1
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Forcellati MR, Green TL, Watanabe A. Brain shapes of large-bodied, flightless ratites (Aves: Palaeognathae) emerge through distinct developmental allometries. ROYAL SOCIETY OPEN SCIENCE 2024; 11:240765. [PMID: 39263457 PMCID: PMC11387061 DOI: 10.1098/rsos.240765] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/10/2024] [Revised: 07/27/2024] [Accepted: 07/31/2024] [Indexed: 09/13/2024]
Abstract
Comparative neuroanatomical studies have long debated the role of development in the evolution of novel and disparate brain morphologies. Historically, these studies have emphasized whether evolutionary shifts along conserved or distinct developmental allometric trends cause changes in brain morphologies. However, the degree to which interspecific differences between variably sized taxa originate through modifying developmental allometry remains largely untested. Taxa with disparate brain shapes and sizes thus allow for investigation into how developmental trends contribute to neuroanatomical diversification. Here, we examine a developmental series of large-bodied ratite birds (approx. 60-140 kg). We use three-dimensional geometric morphometrics on cephalic endocasts of common ostriches, emus and southern cassowaries and compare their developmental trajectories with those of the more modestly sized domestic chicken, previously shown to be in the same allometric grade as ratites. The results suggest that ratites and chickens exhibit disparate endocranial shapes not simply accounted for by their size differences. When shape and age are examined, chickens partly exhibit more accelerated and mature brain shapes than ratites of similar size and age. Taken together, our study indicates that disparate brain shapes between these differently sized taxa have emerged from the evolution of distinct developmental allometries, rather than simply following conserved scaling trends.
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Affiliation(s)
- Meghan R Forcellati
- Department of Ecology, Evolution, and Environmental Biology, Columbia University, New York, NY 10027, USA
- Richard Gilder Graduate School, American Museum of Natural History, New York, NY 10024, USA
| | - Todd L Green
- Biomedical and Anatomical Sciences, New York Institute of Technology, College of Osteopathic Medicine at Arkansas State University, Jonesboro, AR 72401, USA
- Department of Anatomy, New York Institute of Technology, College of Osteopathic Medicine, Old Westbury, NY 11568, USA
| | - Akinobu Watanabe
- Department of Anatomy, New York Institute of Technology, College of Osteopathic Medicine, Old Westbury, NY 11568, USA
- Division of Paleontology, American Museum of Natural History, New York, NY 10024, USA
- Life Sciences Department, Natural History Museum, London SW7 5BD, UK
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2
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Mangalam M, Isoyama Y, Ogata H, Nose-Ogura S, Kayaba M, Nagai N, Kiyono K. Multi-scaling allometry in human development, mammalian morphology, and tree growth. Sci Rep 2024; 14:19957. [PMID: 39198500 PMCID: PMC11358500 DOI: 10.1038/s41598-024-69199-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2024] [Accepted: 08/01/2024] [Indexed: 09/01/2024] Open
Abstract
Various animal and plant species exhibit allometric relationships among their respective traits, wherein one trait undergoes expansion as a power-law function of another due to constraints acting on growth processes. For instance, the acknowledged consensus posits that tree height scales with the two-thirds power of stem diameter. In the context of human development, it is posited that body weight scales with the second power of height. This prevalent allometric relationship derives its nomenclature from fitting two variables linearly within a logarithmic framework, thus giving rise to the term "power-law relationship." Here, we challenge the conventional assumption that a singular power-law equation adequately encapsulates the allometric relationship between any two traits. We strategically leverage quantile regression analysis to demonstrate that the scaling exponent characterizing this power-law relationship is contingent upon the centile within these traits' distributions. This observation fundamentally underscores the proposition that individuals occupying disparate segments of the distribution may employ distinct growth strategies, as indicated by distinct power-law exponents. We introduce the innovative concept of "multi-scale allometry" to encapsulate this newfound insight. Through a comprehensive reevaluation of (i) the height-weight relationship within a cohort comprising 7, 863, 520 Japanese children aged 5-17 years for which the age, sex, height, and weight were recorded as part of a national study, (ii) the stem-diameter-height and crown-radius-height relationships within an expansive sample of 498, 838 georeferenced and taxonomically standardized records of individual trees spanning diverse geographical locations, and (iii) the brain-size-body-size relationship within an extensive dataset encompassing 1, 552 mammalian species, we resolutely substantiate the viability of multi-scale allometric analysis. This empirical substantiation advocates a paradigm shift from uni-scaling to multi-scaling allometric modeling, thereby affording greater prominence to the inherent growth processes that underlie the morphological diversity evident throughout the living world.
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Affiliation(s)
- Madhur Mangalam
- Division of Biomechanics and Research Development, Department of Biomechanics, Center for Research in Human Movement Variability, University of Nebraska at Omaha, Omaha, NE, 68182, USA.
| | - Yosuke Isoyama
- Graduate School of Engineering Science, Osaka University, Osaka, 560-8531, Japan
| | - Hitomi Ogata
- Graduate School of Humanities and Social Sciences, Hiroshima University, Hiroshima, 739-8521, Japan
| | - Sayaka Nose-Ogura
- Department of Sports Medicine and Research, Japan High-Performance Sport Center, Japan Institute Sports Sciences, Tokyo, 115-0056, Japan
- Department of Obstetrics and Gynecology, University of Tokyo Hospital, Tokyo, 113-8655, Japan
| | - Momoko Kayaba
- Faculty of Medicine, University of Tsukuba, Tsukuba, 305-8577, Japan
| | - Narumi Nagai
- School of Human Science and Environment, University of Hyogo, Himeji, 670-0092, Japan
| | - Ken Kiyono
- Graduate School of Engineering Science, Osaka University, Osaka, 560-8531, Japan
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3
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Hawkes K. Life history impacts on infancy and the evolution of human social cognition. Front Psychol 2023; 14:1197378. [PMID: 38023007 PMCID: PMC10666779 DOI: 10.3389/fpsyg.2023.1197378] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Accepted: 10/06/2023] [Indexed: 12/01/2023] Open
Abstract
Greater longevity, slower maturation and shorter birth intervals are life history features that distinguish humans from the other living members of our hominid family, the great apes. Theory and evidence synthesized here suggest the evolution of those features can explain both our bigger brains and our cooperative sociality. I rely on Sarah Hrdy's hypothesis that survival challenges for ancestral infants propelled the evolution of distinctly human socioemotional appetites and Barbara Finlay and colleagues' findings that mammalian brain size is determined by developmental duration. Similar responsiveness to varying developmental contexts in chimpanzee and human one-year-olds suggests similar infant responsiveness in our nearest common ancestor. Those ancestral infants likely began to acquire solid food while still nursing and fed themselves at weaning as chimpanzees and other great apes do now. When human ancestors colonized habitats lacking foods that infants could handle, dependents' survival became contingent on subsidies. Competition to engage subsidizers selected for capacities and tendencies to enlist and maintain social connections during the early wiring of expanding infant brains with lifelong consequences that Hrdy labeled "emotionally modern" social cognition.
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Affiliation(s)
- Kristen Hawkes
- Department of Anthropology, College of Social and Behavioral Science, University of Utah, Salt Lake City, UT, United States
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4
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Dunbar RIM, Shultz S. Four errors and a fallacy: pitfalls for the unwary in comparative brain analyses. Biol Rev Camb Philos Soc 2023; 98:1278-1309. [PMID: 37001905 DOI: 10.1111/brv.12953] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Revised: 03/17/2023] [Accepted: 03/17/2023] [Indexed: 04/03/2023]
Abstract
Comparative analyses are the backbone of evolutionary analysis. However, their record in producing a consensus has not always been good. This is especially true of attempts to understand the factors responsible for the evolution of large brains, which have been embroiled in an increasingly polarised debate over the past three decades. We argue that most of these disputes arise from a number of conceptual errors and associated logical fallacies that are the result of a failure to adopt a biological systems-based approach to hypothesis-testing. We identify four principal classes of error: a failure to heed Tinbergen's Four Questions when testing biological hypotheses, misapplying Dobzhansky's Dictum when testing hypotheses of evolutionary adaptation, poorly chosen behavioural proxies for underlying hypotheses, and the use of inappropriate statistical methods. In the interests of progress, we urge a more careful and considered approach to comparative analyses, and the adoption of a broader, rather than a narrower, taxonomic perspective.
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Affiliation(s)
- Robin I M Dunbar
- Department of Experimental Psychology, Anna Watts Building, University of Oxford, Oxford, OX2 6GG, UK
| | - Susanne Shultz
- Department of Earth and Environmental Sciences, Michael Smith Building, University of Manchester, Manchester, M13 9PT, UK
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5
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Goswami A, Noirault E, Coombs EJ, Clavel J, Fabre AC, Halliday TJD, Churchill M, Curtis A, Watanabe A, Simmons NB, Beatty BL, Geisler JH, Fox DL, Felice RN. Developmental origin underlies evolutionary rate variation across the placental skull. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220083. [PMID: 37183904 PMCID: PMC10184245 DOI: 10.1098/rstb.2022.0083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/16/2023] Open
Abstract
The placental skull has evolved into myriad forms, from longirostrine whales to globular primates, and with a diverse array of appendages from antlers to tusks. This disparity has recently been studied from the perspective of the whole skull, but the skull is composed of numerous elements that have distinct developmental origins and varied functions. Here, we assess the evolution of the skull's major skeletal elements, decomposed into 17 individual regions. Using a high-dimensional morphometric approach for a dataset of 322 living and extinct eutherians (placental mammals and their stem relatives), we quantify patterns of variation and estimate phylogenetic, allometric and ecological signal across the skull. We further compare rates of evolution across ecological categories and ordinal-level clades and reconstruct rates of evolution along lineages and through time to assess whether developmental origin or function discriminate the evolutionary trajectories of individual cranial elements. Our results demonstrate distinct macroevolutionary patterns across cranial elements that reflect the ecological adaptations of major clades. Elements derived from neural crest show the fastest rates of evolution, but ecological signal is equally pronounced in bones derived from neural crest and paraxial mesoderm, suggesting that developmental origin may influence evolutionary tempo, but not capacity for specialisation. This article is part of the theme issue 'The mammalian skull: development, structure and function'.
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Affiliation(s)
- Anjali Goswami
- Department of Life Sciences, Natural History Museum, London SW7 5BD, UK
- Department of Genetics, Evolution, and Environment, University College London, London WC1E 6BT, UK
| | - Eve Noirault
- Department of Life Sciences, Natural History Museum, London SW7 5BD, UK
| | - Ellen J Coombs
- Department of Life Sciences, Natural History Museum, London SW7 5BD, UK
- Department of Genetics, Evolution, and Environment, University College London, London WC1E 6BT, UK
- Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, DC 20013, USA
| | - Julien Clavel
- Université Lyon, Université Claude Bernard Lyon 1, CNRS, ENTPE, UMR 5023 LEHNA, 69622 Villeurbanne, France
| | - Anne-Claire Fabre
- Department of Life Sciences, Natural History Museum, London SW7 5BD, UK
- Naturhistorisches Museum Bern, 3005 Bern, Switzerland
- Institute of Ecology and Evolution, University of Bern, 3012 Bern, Switzerland
| | - Thomas J D Halliday
- Department of Life Sciences, Natural History Museum, London SW7 5BD, UK
- School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham B15 2TT, UK
| | - Morgan Churchill
- Department of Biology, University of Wisconsin Oshkosh, Oshkosh, WI 54901, USA
| | - Abigail Curtis
- Department of Biology, University of Washington, Seattle, WA 98195, USA
| | - Akinobu Watanabe
- Department of Life Sciences, Natural History Museum, London SW7 5BD, UK
- Department of Anatomy, College of Osteopathic Medicine, New York Institute of Technology, Old Westbury, NY 11568, USA
- Division of Paleontology, American Museum of Natural History, New York, NY 10024, USA
| | - Nancy B Simmons
- Department of Mammalogy, Division of Vertebrate Zoology, American Museum of Natural History, New York, NY 10024, USA
| | - Brian L Beatty
- Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, DC 20013, USA
- Department of Anatomy, College of Osteopathic Medicine, New York Institute of Technology, Old Westbury, NY 11568, USA
| | - Jonathan H Geisler
- Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, DC 20013, USA
- Department of Anatomy, College of Osteopathic Medicine, New York Institute of Technology, Old Westbury, NY 11568, USA
| | - David L Fox
- Department of Earth and Environmental Sciences, University of Minnesota, Minneapolis, MN 55455, USA
| | - Ryan N Felice
- Department of Life Sciences, Natural History Museum, London SW7 5BD, UK
- Department of Genetics, Evolution, and Environment, University College London, London WC1E 6BT, UK
- Centre for Integrative Anatomy, Department of Cell and Developmental Biology, University College London, London WC1E 6BT, UK
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6
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Roston RA, Boessenecker RW, Geisler JH. Evolution and development of the cetacean skull roof: a case study in novelty and homology. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220086. [PMID: 37183892 PMCID: PMC10184229 DOI: 10.1098/rstb.2022.0086] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2022] [Accepted: 11/15/2022] [Indexed: 05/16/2023] Open
Abstract
Skulls of living whales and dolphins (cetaceans) are telescoped-bones of the skull roof are overlapped by expanded facial bones and/or anteriorly extended occipital bones. Evolution of the underlying skull roof (calvarium), which lies between the telescoped regions, is relatively unstudied. We explore the evolution and development of the calvarium of toothed whales (odontocetes) by integrating fetal data with Oligocene odontocete fossils from North America, including eight neonatal and juvenile skulls of Olympicetus†. We identified two potential synapomorphies of crown Cetacea: contact of interparietals with frontals, and a single anterior median interparietal (AMI) element. Within Odontoceti, loss of contact between the parietals diagnoses the clade including Delphinida, Ziphiidae and Platanistidae (=Synrhina). Delphinida is characterized by a greatly enlarged interparietal. New fetal series of delphinoids reveal a consistent developmental pattern with three elements: the AMI and bilateral posterior interparietals (PIs). The PIs most resemble the medial interparietal elements of terrestrial artiodactyls, suggesting that the AMI of cetaceans could be a unique ossification. More broadly, the paucity of conserved anatomical relationships of the interparietals, as well as the fact that the elements often do not coalesce into a single bone, demonstrates that assessing homology of the interparietals across mammals remains challenging. This article is part of the theme issue 'The mammalian skull: development, structure and function'.
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Affiliation(s)
- R. A. Roston
- Department of Oral Health Sciences, School of Dentistry, University of Washington, Seattle, WA 98195, USA
- Center for Developmental Biology and Regenerative Medicine, Seattle Children's Research Institute, Seattle, WA 98101, USA
| | - R. W. Boessenecker
- Department of Geology and Environmental Geosciences, College of Charleston, Charleston, SC 29424, USA
- University of California Museum of Paleontology, University of California, Berkeley, CA 94720, USA
| | - J. H. Geisler
- Department of Anatomy, College of Osteopathic Medicine, New York Institute of Technology, Old Westbury, NY 11568, USA
- Department of Paleobiology, National Museum of Natural History, Washington, DC 20560, USA
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7
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Pohle AK, Zalewski A, Muturi M, Dullin C, Farková L, Keicher L, Dechmann DKN. Domestication effect of reduced brain size is reverted when mink become feral. ROYAL SOCIETY OPEN SCIENCE 2023; 10:230463. [PMID: 37416828 PMCID: PMC10320332 DOI: 10.1098/rsos.230463] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Accepted: 06/12/2023] [Indexed: 07/08/2023]
Abstract
A typical consequence of breeding animal species for domestication is a reduction in relative brain size. When domesticated animals escape from captivity and establish feral populations, the larger brain of the wild phenotype is usually not regained. In the American mink (Neovison vison), we found an exception to this rule. We confirmed the previously described reduction in relative braincase size and volume compared to their wild North American ancestors in mink bred for their fur in Poland, in a dataset of 292 skulls. We then also found a significant regrowth of these measures in well-established feral populations in Poland. Closely related, small mustelids are known for seasonal reversible changes in skull and brain size. It seems that these small mustelids are able to regain the brain size, which is adaptive for living in the wild, and flexibly respond to selection accordingly.
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Affiliation(s)
- Ann-Kathrin Pohle
- Department of Migration, Max Planck Institute of Animal Behavior, Am Obstberg 1, 78315 Radolfzell, Germany
- Department for the Ecology of Animal Societies, Max Planck Institute of Animal Behavior, Bücklestraße 5a, 78467 Konstanz, Germany
- University of Konstanz, Universitätsstraße 10, 78457 Konstanz, Germany
| | - Andrzej Zalewski
- Mammal Research Institute, Polish Academy of Sciences, 17-230 Białowieża, Poland
| | - Marion Muturi
- Department of Migration, Max Planck Institute of Animal Behavior, Am Obstberg 1, 78315 Radolfzell, Germany
| | - Christian Dullin
- Department for Diagnostic and Interventional Radiology, University Medical Center Goettingen, Robert-Koch-Straße 40, 37075 Goettingen, Germany
- Department Translational Molecular Imaging, Max Planck Institute for Multidisciplinary Sciences, Herman-Rein-Straße 3, 37075 Goettingen, Germany
- Department for Diagnostic and Interventional Radiology, University Hospital Heidelberg, Im Neuenheimer Feld 420, 69120 Heidelberg, Germany
| | - Lucie Farková
- Department of Migration, Max Planck Institute of Animal Behavior, Am Obstberg 1, 78315 Radolfzell, Germany
- Department of Zoology, Charles University, Viničná 7, 128 00 Prague, Czech Republic
| | - Lara Keicher
- Department of Migration, Max Planck Institute of Animal Behavior, Am Obstberg 1, 78315 Radolfzell, Germany
- University of Konstanz, Universitätsstraße 10, 78457 Konstanz, Germany
| | - Dina K. N. Dechmann
- Department of Migration, Max Planck Institute of Animal Behavior, Am Obstberg 1, 78315 Radolfzell, Germany
- University of Konstanz, Universitätsstraße 10, 78457 Konstanz, Germany
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8
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The impact of environmental factors on the evolution of brain size in carnivorans. Commun Biol 2022; 5:998. [PMID: 36130990 PMCID: PMC9492690 DOI: 10.1038/s42003-022-03748-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Accepted: 07/20/2022] [Indexed: 11/28/2022] Open
Abstract
The reasons why some animals have developed larger brains has long been a subject of debate. Yet, it remains unclear which selective pressures may favour the encephalization and how it may act during evolution at different taxonomic scales. Here we studied the patterns and tempo of brain evolution within the order Carnivora and present large-scale comparative analysis of the effect of ecological, environmental, social, and physiological variables on relative brain size in a sample of 174 extant carnivoran species. We found a complex pattern of brain size change between carnivoran families with differences in both the rate and diversity of encephalization. Our findings suggest that during carnivorans’ evolution, a trade-off have occurred between the cognitive advantages of acquiring a relatively large brain allowing to adapt to specific environments, and the metabolic costs of the brain which may constitute a disadvantage when facing the need to colonize new environments. The brain size of carnivores has evolved to balance a trade-off between increased cognitive function and increased metabolic cost.
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9
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Abstract
The reasons why some animals have developed larger brains has long been a subject of debate. Yet, it remains unclear which selective pressures may favour the encephalization and how it may act during evolution at different taxonomic scales. Here we studied the patterns and tempo of brain evolution within the order Carnivora and present large-scale comparative analysis of the effect of ecological, environmental, social, and physiological variables on relative brain size in a sample of 174 extant carnivoran species. We found a complex pattern of brain size change between carnivoran families with differences in both the rate and diversity of encephalization. Our findings suggest that during carnivorans' evolution, a trade-off have occurred between the cognitive advantages of acquiring a relatively large brain allowing to adapt to specific environments, and the metabolic costs of the brain which may constitute a disadvantage when facing the need to colonize new environments.
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10
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Lynch LM, Allen KL. Relative Brain Volume of Carnivorans Has Evolved in Correlation with Environmental and Dietary Variables Differentially among Clades. BRAIN, BEHAVIOR AND EVOLUTION 2022; 97:284-297. [PMID: 35235933 DOI: 10.1159/000523787] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2021] [Accepted: 02/16/2022] [Indexed: 12/21/2022]
Abstract
Carnivorans possess relatively large brains compared to most other mammalian clades. Factors like environmental complexity (Cognitive Buffer Hypothesis) and diet quality (Expensive-Tissue Hypothesis) have been proposed as mechanisms for encephalization in other large-brained clades. We examine whether the Cognitive Buffer and Expensive-Tissue Hypotheses account for brain size variation within Carnivora. Under these hypotheses, we predict a positive correlation between brain size and environmental complexity or protein consumption. Relative endocranial volume (phylogenetic generalized least-squares residual from species' mean body mass) and 9 environmental and dietary variables were collected from the literature for 148 species of terrestrial and marine carnivorans. We found that the correlation between relative brain volume and environment and diet differed among clades, a trend consistent with other larger brained vertebrates (i.e., Primates, Aves). Mustelidae and Procyonidae demonstrate larger brains in species with higher-quality diets, consistent with the Expensive-Tissue Hypothesis, while in Herpestidae, correlations between relative brain size and environment are consistent with the Cognitive Buffer Hypothesis. Our results indicate that carnivorans may have evolved relatively larger brains under similar selective pressures as primates despite the considerable differences in life history and behavior between these two clades.
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Affiliation(s)
- Leigha M Lynch
- Washington University School of Medicine in St. Louis, St. Louis, Missouri, USA.,Midwestern University, Glendale, Arizona, USA
| | - Kari L Allen
- Washington University School of Medicine in St. Louis, St. Louis, Missouri, USA
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11
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Percival CJ, Devine J, Hassan CR, Vidal‐Garcia M, O'Connor‐Coates CJ, Zaffarini E, Roseman C, Katz D, Hallgrimsson B. The genetic basis of neurocranial size and shape across varied lab mouse populations. J Anat 2022; 241:211-229. [PMID: 35357006 PMCID: PMC9296060 DOI: 10.1111/joa.13657] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Revised: 02/11/2022] [Accepted: 03/08/2022] [Indexed: 11/26/2022] Open
Abstract
Brain and skull tissues interact through molecular signalling and mechanical forces during head development, leading to a strong correlation between the neurocranium and the external brain surface. Therefore, when brain tissue is unavailable, neurocranial endocasts are often used to approximate brain size and shape. Evolutionary changes in brain morphology may have resulted in secondary changes to neurocranial morphology, but the developmental and genetic processes underlying this relationship are not well understood. Using automated phenotyping methods, we quantified the genetic basis of endocast variation across large genetically varied populations of laboratory mice in two ways: (1) to determine the contributions of various genetic factors to neurocranial form and (2) to help clarify whether a neurocranial variation is based on genetic variation that primarily impacts bone development or on genetic variation that primarily impacts brain development, leading to secondary changes in bone morphology. Our results indicate that endocast size is highly heritable and is primarily determined by additive genetic factors. In addition, a non-additive inbreeding effect led to founder strains with lower neurocranial size, but relatively large brains compared to skull size; suggesting stronger canalization of brain size and/or a general allometric effect. Within an outbred sample of mice, we identified a locus on mouse chromosome 1 that is significantly associated with variation in several positively correlated endocast size measures. Because the protein-coding genes at this locus have been previously associated with brain development and not with bone development, we propose that genetic variation at this locus leads primarily to variation in brain volume that secondarily leads to changes in neurocranial globularity. We identify a strain-specific missense mutation within Akt3 that is a strong causal candidate for this genetic effect. Whilst it is not appropriate to generalize our hypothesis for this single locus to all other loci that also contribute to the complex trait of neurocranial skull morphology, our results further reveal the genetic basis of neurocranial variation and highlight the importance of the mechanical influence of brain growth in determining skull morphology.
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Affiliation(s)
| | - Jay Devine
- Cell Biology and AnatomyUniversity of Calgary Cumming School of MedicineCalgaryCanada
| | | | - Marta Vidal‐Garcia
- Cell Biology and AnatomyUniversity of Calgary Cumming School of MedicineCalgaryCanada
| | | | - Eva Zaffarini
- Cell Biology and AnatomyUniversity of Calgary Cumming School of MedicineCalgaryCanada
| | - Charles Roseman
- Department of Evolution, Ecology, and BehaviorUniversity of IllinoisUrbanaIllinoisUSA
| | - David Katz
- Cell Biology and AnatomyUniversity of Calgary Cumming School of MedicineCalgaryCanada
| | - Benedikt Hallgrimsson
- Cell Biology and Anatomy, Alberta Children's Hospital Research Institute, Cumming School of MedicineUniversity of CalgaryCalgaryCanada
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12
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Neuron numbers link innovativeness with both absolute and relative brain size in birds. Nat Ecol Evol 2022; 6:1381-1389. [PMID: 35817825 DOI: 10.1038/s41559-022-01815-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2021] [Accepted: 05/19/2022] [Indexed: 12/31/2022]
Abstract
A longstanding issue in biology is whether the intelligence of animals can be predicted by absolute or relative brain size. However, progress has been hampered by an insufficient understanding of how neuron numbers shape internal brain organization and cognitive performance. On the basis of estimations of neuron numbers for 111 bird species, we show here that the number of neurons in the pallial telencephalon is positively associated with a major expression of intelligence: innovation propensity. The number of pallial neurons, in turn, is greater in brains that are larger in both absolute and relative terms and positively covaries with longer post-hatching development periods. Thus, our analyses show that neuron numbers link cognitive performance to both absolute and relative brain size through developmental adjustments. These findings help unify neuro-anatomical measures at multiple levels, reconciling contradictory views over the biological significance of brain expansion. The results also highlight the value of a life history perspective to advance our understanding of the evolutionary bases of the connections between brain and cognition.
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13
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Bertrand OC, Shelley SL, Williamson TE, Wible JR, Chester SGB, Flynn JJ, Holbrook LT, Lyson TR, Meng J, Miller IM, Püschel HP, Smith T, Spaulding M, Tseng ZJ, Brusatte SL. Brawn before brains in placental mammals after the end-Cretaceous extinction. Science 2022; 376:80-85. [PMID: 35357913 DOI: 10.1126/science.abl5584] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Mammals are the most encephalized vertebrates, with the largest brains relative to body size. Placental mammals have particularly enlarged brains, with expanded neocortices for sensory integration, the origins of which are unclear. We used computed tomography scans of newly discovered Paleocene fossils to show that contrary to the convention that mammal brains have steadily enlarged over time, early placentals initially decreased their relative brain sizes because body mass increased at a faster rate. Later in the Eocene, multiple crown lineages independently acquired highly encephalized brains through marked growth in sensory regions. We argue that the placental radiation initially emphasized increases in body size as extinction survivors filled vacant niches. Brains eventually became larger as ecosystems saturated and competition intensified.
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Affiliation(s)
- Ornella C Bertrand
- School of GeoSciences, University of Edinburgh, Grant Institute, Edinburgh, Scotland EH9 3FE, UK
| | - Sarah L Shelley
- School of GeoSciences, University of Edinburgh, Grant Institute, Edinburgh, Scotland EH9 3FE, UK.,Section of Mammals, Carnegie Museum of Natural History, Pittsburgh, PA, USA
| | | | - John R Wible
- Section of Mammals, Carnegie Museum of Natural History, Pittsburgh, PA, USA
| | - Stephen G B Chester
- Department of Anthropology, Brooklyn College, City University of New York, Brooklyn, NY, USA.,Department of Anthropology, The Graduate Center, City University of New York, New York, NY, USA.,New York Consortium in Evolutionary Primatology, New York, NY, USA
| | - John J Flynn
- Division of Paleontology, American Museum of Natural History, New York, NY, USA.,Department of Earth and Environmental Sciences, Columbia University, New York, NY, USA.,Ecology, Evolutionary Biology, and Behavior subprogram, PhD Program in Biology, The Graduate Center, City University of New York, New York, NY, USA.,PhD Program in Earth and Environmental Sciences, The Graduate Center, City University of New York, New York, NY, USA
| | - Luke T Holbrook
- Department of Biological Sciences, Rowan University, Glassboro, NJ, USA
| | | | - Jin Meng
- Division of Paleontology, American Museum of Natural History, New York, NY, USA
| | - Ian M Miller
- Denver Museum of Nature & Science, Denver, CO, USA.,National Geographic Society, Washington, DC, USA
| | - Hans P Püschel
- School of GeoSciences, University of Edinburgh, Grant Institute, Edinburgh, Scotland EH9 3FE, UK
| | - Thierry Smith
- Directorate Earth and History of Life, Royal Belgian Institute of Natural Sciences, Brussels, Belgium
| | - Michelle Spaulding
- Department of Biological Sciences, Purdue University Northwest, Westville, IN, USA
| | - Z Jack Tseng
- Department of Integrative Biology and Museum of Paleontology, University of California, Berkeley, CA, USA
| | - Stephen L Brusatte
- School of GeoSciences, University of Edinburgh, Grant Institute, Edinburgh, Scotland EH9 3FE, UK.,New Mexico Museum of Natural History and Science, Albuquerque, NM, USA
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14
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MacIver MA, Finlay BL. The neuroecology of the water-to-land transition and the evolution of the vertebrate brain. Philos Trans R Soc Lond B Biol Sci 2022; 377:20200523. [PMID: 34957852 PMCID: PMC8710882 DOI: 10.1098/rstb.2020.0523] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The water-to-land transition in vertebrate evolution offers an unusual opportunity to consider computational affordances of a new ecology for the brain. All sensory modalities are changed, particularly a greatly enlarged visual sensorium owing to air versus water as a medium, and expanded by mobile eyes and neck. The multiplication of limbs, as evolved to exploit aspects of life on land, is a comparable computational challenge. As the total mass of living organisms on land is a hundredfold larger than the mass underwater, computational improvements promise great rewards. In water, the midbrain tectum coordinates approach/avoid decisions, contextualized by water flow and by the animal's body state and learning. On land, the relative motions of sensory surfaces and effectors must be resolved, adding on computational architectures from the dorsal pallium, such as the parietal cortex. For the large-brained and long-living denizens of land, making the right decision when the wrong one means death may be the basis of planning, which allows animals to learn from hypothetical experience before enactment. Integration of value-weighted, memorized panoramas in basal ganglia/frontal cortex circuitry, with allocentric cognitive maps of the hippocampus and its associated cortices becomes a cognitive habit-to-plan transition as substantial as the change in ecology. This article is part of the theme issue 'Systems neuroscience through the lens of evolutionary theory'.
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Affiliation(s)
- Malcolm A. MacIver
- Center for Robotics and Biosystems, Northwestern University, Evanston, IL 60208, USA
| | - Barbara L. Finlay
- Department of Psychology, Behavioral and Evolutionary Neuroscience Group, Cornell University, Ithaca, NY 14850, USA
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15
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Závorka L, Koene JP, Armstrong TA, Fehlinger L, Adams CE. Differences in brain morphology of brown trout across stream, lake, and hatchery environments. Ecol Evol 2022; 12:e8684. [PMID: 35309753 PMCID: PMC8902666 DOI: 10.1002/ece3.8684] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Revised: 02/07/2022] [Accepted: 02/09/2022] [Indexed: 11/11/2022] Open
Abstract
It has been suggested that a trade-off between cognitive capacity and developmental costs may drive brain size and morphology across fish species, but this pattern is less well explored at the intraspecific level. Physical habitat complexity has been proposed as a key selection pressure on cognitive capacity that shapes brain morphology of fishes. In this study, we compared brain morphology of brown trout, Salmo trutta, from stream, lake, and hatchery environments, which generally differ in physical complexity ranging from low habitat complexity in the hatchery to high habitat complexity in streams and intermediate complexity in lakes. We found that brain size, and the size of optic tectum and telencephalon differed across the three habitats, both being largest in lake fish with a tendency to be smaller in the stream compared to hatchery fish. Therefore, our findings do not support the hypothesis that in brown trout the volume of brain and its regions important for navigation and decision-making increases in physically complex habitats. We suggest that the observed differences in brain size might be associated with diet quality and habitat-specific behavioral adaptations rather than physical habitat complexity.
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Affiliation(s)
- Libor Závorka
- WasserCluster Lunz – Inter‐University Centre for Aquatic Ecosystem ResearchLunz am SeeAustria
- Institute of Biodiversity, Animal Health and Comparative MedicineCollege of Medical, Veterinary and Life SciencesUniversity of GlasgowGlasgowUK
| | - J. Peter Koene
- Institute of Biodiversity, Animal Health and Comparative MedicineCollege of Medical, Veterinary and Life SciencesUniversity of GlasgowGlasgowUK
- Scottish Centre for Ecology and the Natural Environment (SCENE)University of GlasgowGlasgowUK
| | - Tiffany A. Armstrong
- Institute of Biodiversity, Animal Health and Comparative MedicineCollege of Medical, Veterinary and Life SciencesUniversity of GlasgowGlasgowUK
| | - Lena Fehlinger
- WasserCluster Lunz – Inter‐University Centre for Aquatic Ecosystem ResearchLunz am SeeAustria
| | - Colin E. Adams
- Scottish Centre for Ecology and the Natural Environment (SCENE)University of GlasgowGlasgowUK
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16
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Chambers HR, Heldstab SA, O’Hara SJ. Why big brains? A comparison of models for both primate and carnivore brain size evolution. PLoS One 2021; 16:e0261185. [PMID: 34932586 PMCID: PMC8691615 DOI: 10.1371/journal.pone.0261185] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Accepted: 11/24/2021] [Indexed: 11/19/2022] Open
Abstract
Despite decades of research, much uncertainty remains regarding the selection pressures responsible for brain size variation. Whilst the influential social brain hypothesis once garnered extensive support, more recent studies have failed to find support for a link between brain size and sociality. Instead, it appears there is now substantial evidence suggesting ecology better predicts brain size in both primates and carnivores. Here, different models of brain evolution were tested, and the relative importance of social, ecological, and life-history traits were assessed on both overall encephalisation and specific brain regions. In primates, evidence is found for consistent associations between brain size and ecological factors, particularly diet; however, evidence was also found advocating sociality as a selection pressure driving brain size. In carnivores, evidence suggests ecological variables, most notably home range size, are influencing brain size; whereas, no support is found for the social brain hypothesis, perhaps reflecting the fact sociality appears to be limited to a select few taxa. Life-history associations reveal complex selection mechanisms to be counterbalancing the costs associated with expensive brain tissue through extended developmental periods, reduced fertility, and extended maximum lifespan. Future studies should give careful consideration of the methods chosen for measuring brain size, investigate both whole brain and specific brain regions where possible, and look to integrate multiple variables, thus fully capturing all of the potential factors influencing brain size.
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Affiliation(s)
- Helen Rebecca Chambers
- School of Science, Engineering & Environment, University of Salford, Salford, Greater Manchester, United Kingdom
| | | | - Sean J. O’Hara
- School of Science, Engineering & Environment, University of Salford, Salford, Greater Manchester, United Kingdom
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17
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Sowersby W, Eckerström-Liedholm S, Kotrschal A, Näslund J, Rowiński P, Gonzalez-Voyer A, Rogell B. Fast life-histories are associated with larger brain size in killifishes. Evolution 2021; 75:2286-2298. [PMID: 34270088 DOI: 10.1111/evo.14310] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Revised: 06/11/2021] [Accepted: 06/25/2021] [Indexed: 11/27/2022]
Abstract
The high energetic demands associated with the vertebrate brain are proposed to result in a trade-off between the pace of life-history and relative brain size. However, because both life-history and brain size also have a strong relationship with body size, any associations between the pace of life-history and relative brain size may be confounded by coevolution with body size. Studies on systems where contrasts in the pace of life-history occur without concordant contrasts in body size could therefore add to our understanding of the potential coevolution between relative brain size and life-history. Using one such system - 21 species of killifish - we employed a common garden design across two ontogenetic stages to investigate the association between relative brain size and the pace of life-history. Contrary to predictions, we found that relative brain size was larger in adult fast-living killifishes, compared to slow-living species. Although we found no differences in relative brain size between juvenile killifishes. Our results suggest that fast- and slow-living killifishes do not exhibit the predicted trade-off between brain size and life-history. Instead, fast and slow-living killifishes could differ in the ontogenetic timing of somatic versus neural growth or inhabit environments that differ considerably in cognitive demands.
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Affiliation(s)
- Will Sowersby
- Department of Zoology, Stockholm University, Stockholm, Sweden.,Department of Biology, Osaka City University, Osaka, Japan
| | - Simon Eckerström-Liedholm
- Department of Zoology, Stockholm University, Stockholm, Sweden.,Wild Animal Initiative, Farmington, Minnesota, USA
| | - Alexander Kotrschal
- Department of Zoology, Stockholm University, Stockholm, Sweden.,Department of Animal Sciences: Behavioural Ecology, Wageningen University, Wageningen, Netherlands
| | - Joacim Näslund
- Department of Zoology, Stockholm University, Stockholm, Sweden.,Department of Aquatic Resources, Institute of Freshwater Research, Swedish University of Agricultural Sciences, Drottningholm, Sweden
| | - Piotr Rowiński
- Department of Zoology, Stockholm University, Stockholm, Sweden
| | - Alejandro Gonzalez-Voyer
- Department of Zoology, Stockholm University, Stockholm, Sweden.,Instituto de Ecología, Universidad Nacional Autónoma de México, México, Mexico
| | - Björn Rogell
- Department of Zoology, Stockholm University, Stockholm, Sweden.,Department of Aquatic Resources, Institute of Freshwater Research, Swedish University of Agricultural Sciences, Drottningholm, Sweden
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18
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Elizondo Lara LC, Young J, Schliep K, De León LF. Brain Allometry Across Macroevolutionary Scales in Squamates Suggests a Conserved Pattern in Snakes. ZOOLOGY 2021; 146:125926. [PMID: 33932854 DOI: 10.1016/j.zool.2021.125926] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Revised: 04/03/2021] [Accepted: 04/07/2021] [Indexed: 11/24/2022]
Abstract
Despite historical interest in brain size evolution in vertebrates, few studies have assessed variation in brain size in squamate reptiles such as snakes and lizards. Here, we analyzed the pattern of brain allometry at macroevolutionary scale in snakes and lizards, using body mass and snout vent length as measures of body size. We also assessed potential energetic trade-offs associated with relative brain size changes in Crotalinae vipers. Body mass showed a conserved pattern of brain allometry across taxa of snakes, but not in lizards. Body length favored changes of brain allometry in both snakes and lizards, but less variability was observed in snakes. Moreover, we did not find evidence for trade-offs between brain size and the size of other organs in Crotalinae. Thus, despite the contribution of body elongation to changes in relative brain size in squamate reptiles, snakes present low variation in brain allometry across taxa. Although the mechanisms driving this conserved pattern are unknown, we hypothesize that the snake body plan plays an important role in balancing the energetic demands of brain and body size increase at macroevolutionary scales. We encourage future research on the evolution of brain and body size in snakes to test this hypothesis.
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Affiliation(s)
- Luis C Elizondo Lara
- Programa de Maestría en Ciencias Biológicas, Vicerrectoría de Investigación y Postgrado, Universidad de Panamá, Avenida Simón Bolívar, Panama City, Panama, Apartado 3366 Panama 4, Panama; Departamento de Fisiología y Comportamiento Animal, Escuela de Biología, Facultad de Ciencias Naturales, Exactas y Tecnología, Universidad de Panamá, Avenida Simón Bolívar, Panama City, Panama, Apartado 3366 Panama 4, Panama.
| | - José Young
- Departamento de Fisiología y Comportamiento Animal, Escuela de Biología, Facultad de Ciencias Naturales, Exactas y Tecnología, Universidad de Panamá, Avenida Simón Bolívar, Panama City, Panama, Apartado 3366 Panama 4, Panama
| | - Klaus Schliep
- Institute of Computational Biotechnology, Graz University of Technology, Graz, Austria
| | - Luis F De León
- Department of Biology, University of Massachusetts, Boston, USA; Instituto de Investigaciones Científicas y Servicios de Alta Tecnología (INDICASAT-AIP), City of Knowledge, Clayton, Panama
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19
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Todorov OS, Blomberg SP, Goswami A, Sears K, Drhlík P, Peters J, Weisbecker V. Testing hypotheses of marsupial brain size variation using phylogenetic multiple imputations and a Bayesian comparative framework. Proc Biol Sci 2021; 288:20210394. [PMID: 33784860 PMCID: PMC8059968 DOI: 10.1098/rspb.2021.0394] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Accepted: 03/01/2021] [Indexed: 12/20/2022] Open
Abstract
Considerable controversy exists about which hypotheses and variables best explain mammalian brain size variation. We use a new, high-coverage dataset of marsupial brain and body sizes, and the first phylogenetically imputed full datasets of 16 predictor variables, to model the prevalent hypotheses explaining brain size evolution using phylogenetically corrected Bayesian generalized linear mixed-effects modelling. Despite this comprehensive analysis, litter size emerges as the only significant predictor. Marsupials differ from the more frequently studied placentals in displaying a much lower diversity of reproductive traits, which are known to interact extensively with many behavioural and ecological predictors of brain size. Our results therefore suggest that studies of relative brain size evolution in placental mammals may require targeted co-analysis or adjustment of reproductive parameters like litter size, weaning age or gestation length. This supports suggestions that significant associations between behavioural or ecological variables with relative brain size may be due to a confounding influence of the extensive reproductive diversity of placental mammals.
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Affiliation(s)
- Orlin S. Todorov
- School of Biological Sciences, The University of Queensland, St Lucia, Queensland, Australia
| | - Simone P. Blomberg
- School of Biological Sciences, The University of Queensland, St Lucia, Queensland, Australia
| | - Anjali Goswami
- Genetics, Evolution, and Environment Department, University College London, UK
- Department of Life Sciences, Natural History Museum, London, UK
| | - Karen Sears
- Department of Ecology and Evolutionary Biology, College of Life Sciences, University of California Los Angeles, CA, USA
| | - Patrik Drhlík
- Faculty of Mechatronics, Informatics and Interdisciplinary Studies, Technical University of Liberec, Czechia
| | - James Peters
- Department of Animal Biology, University of Illinois at Urbana Champaign, USA
| | - Vera Weisbecker
- School of Biological Sciences, The University of Queensland, St Lucia, Queensland, Australia
- College of Science and Engineering, Flinders University, Australia
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20
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Chen SC, Wu LM, Wang B, Dickie JB. Macroevolutionary patterns in seed component mass and different evolutionary trajectories across seed desiccation responses. THE NEW PHYTOLOGIST 2020; 228:770-777. [PMID: 32463920 DOI: 10.1111/nph.16706] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Accepted: 05/15/2020] [Indexed: 06/11/2023]
Abstract
Seed coat and seed reserve show substantial mass variation, play different roles in plant life strategies and are shaped by different selective forces. However, remarkably little is known about the macroevolution of the relative allocation in seed components and its influence on important ecophysiological processes. Using phylogenetic comparative methods and evolutionary modelling approaches, we modelled mass changes in seed components along individual lineages for 940 species and compared the patterns across seed desiccation responses. Seed component allocation was driven primarily by changes in reserve mass rather than coat mass, as evolutionary rates in reserve mass significantly outpaced those in coat mass. Although the scaling patterns between reserve mass and coat mass were similar across desiccation responses, desiccation-sensitive seeds allocated more and evolved faster in reserve compared to desiccation-tolerant seeds. The findings emphasize the relative importance of reserve to coat in the evolution of plant reproductive strategies, revealing potential ecological advantages gained by enlarged reserve. As the first quantification of the evolutionary tempo and mode of seed component mass, our study allows a detailed interpretation of evolutionary pathways underlying seed storage behaviours and advances the understanding of the evolution of desiccation sensitivity in seeds.
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Affiliation(s)
- Si-Chong Chen
- Millennium Seed Bank, Royal Botanic Gardens Kew, Wakehurst, West Sussex, RH17 6TN, UK
| | - La-Mei Wu
- Centre for Integrative Conservation, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan, 666303, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Bo Wang
- Centre for Integrative Conservation, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan, 666303, China
- School of Resources and Environmental Engineering, Anhui University, Hefei, 230601, China
| | - John B Dickie
- Millennium Seed Bank, Royal Botanic Gardens Kew, Wakehurst, West Sussex, RH17 6TN, UK
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21
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Ocampo D, Sánchez C, Barrantes G. Do Different Methods Yield Equivalent Estimations of Brain Size in Birds? BRAIN, BEHAVIOR AND EVOLUTION 2020; 95:113-122. [PMID: 32866953 DOI: 10.1159/000509383] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2019] [Accepted: 06/11/2020] [Indexed: 11/19/2022]
Abstract
The ratio of brain size to body size (relative brain size) is often used as a measure of relative investment in the brain in ecological and evolutionary studies on a wide range of animal groups. In birds, a variety of methods have been used to measure the brain size part of this ratio, including endocranial volume, fixed brain mass, and fresh brain mass. It is still unclear, however, whether these methods yield the same results. Using data obtained from fresh corpses and from published sources, this study shows that endocranial volume, mass of fixed brain tissue, and fresh mass provide equivalent estimations of brain size for 48 bird families, in 19 orders. We found, however, that the various methods yield significantly different brain size estimates for hummingbirds (Trochilidae). For hummingbirds, fixed brain mass tends to underestimate brain size due to reduced tissue density, whereas endocranial volume overestimates brain size because it includes a larger volume than that occupied by the brain.
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Affiliation(s)
- Diego Ocampo
- Department of Biology, University of Miami, Coral Gables, Florida, USA, .,Escuela de Biología, Universidad de Costa Rica, San José, Costa Rica,
| | - César Sánchez
- Museum of Natural Science and Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana, USA
| | - Gilbert Barrantes
- Escuela de Biología, Universidad de Costa Rica, San José, Costa Rica
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22
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Bowling DL, Dunn JC, Smaers JB, Garcia M, Sato A, Hantke G, Handschuh S, Dengg S, Kerney M, Kitchener AC, Gumpenberger M, Fitch WT. Rapid evolution of the primate larynx? PLoS Biol 2020; 18:e3000764. [PMID: 32780733 PMCID: PMC7418954 DOI: 10.1371/journal.pbio.3000764] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Accepted: 07/08/2020] [Indexed: 12/03/2022] Open
Abstract
Tissue vibrations in the larynx produce most sounds that comprise vocal communication in mammals. Larynx morphology is thus predicted to be a key target for selection, particularly in species with highly developed vocal communication systems. Here, we present a novel database of digitally modeled scanned larynges from 55 different mammalian species, representing a wide range of body sizes in the primate and carnivoran orders. Using phylogenetic comparative methods, we demonstrate that the primate larynx has evolved more rapidly than the carnivoran larynx, resulting in a pattern of larger size and increased deviation from expected allometry with body size. These results imply fundamental differences between primates and carnivorans in the balance of selective forces that constrain larynx size and highlight an evolutionary flexibility in primates that may help explain why we have developed complex and diverse uses of the vocal organ for communication.
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Affiliation(s)
- Daniel L. Bowling
- Department of Psychiatry and Behavioral Sciences, Stanford University, Stanford, California, United States of America
- Department of Behavioral & Cognitive Biology, University of Vienna, Vienna, Austria
| | - Jacob C. Dunn
- Department of Behavioral & Cognitive Biology, University of Vienna, Vienna, Austria
- Behavioural Ecology Research Group, Anglia Ruskin University, Cambridge, United Kingdom
- Biological Anthropology, Department of Archaeology, University of Cambridge, Cambridge, United Kingdom
| | - Jeroen B. Smaers
- Department of Anthropology, Stony Brook University, Stony Brook, New York, United States of America
- Division of Anthropology, American Museum of Natural History, New York City, New York, United States of America
| | - Maxime Garcia
- Department of Behavioral & Cognitive Biology, University of Vienna, Vienna, Austria
- Animal Behaviour, Department of Evolutionary Biology and Environmental Science, University of Zurich, Zurich, Switzerland
| | - Asha Sato
- Center for Language Evolution, University of Edinburgh, Edinburgh, United Kingdom
| | - Georg Hantke
- Department of Natural Sciences, National Museums Scotland, Edinburgh, United Kingdom
| | - Stephan Handschuh
- VetCore Facility for Research, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Sabine Dengg
- Klinische Abteilung für Bildgebende Diagnostik, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Max Kerney
- Behavioural Ecology Research Group, Anglia Ruskin University, Cambridge, United Kingdom
| | - Andrew C. Kitchener
- Department of Natural Sciences, National Museums Scotland, Edinburgh, United Kingdom
| | - Michaela Gumpenberger
- Klinische Abteilung für Bildgebende Diagnostik, University of Veterinary Medicine Vienna, Vienna, Austria
| | - W. Tecumseh Fitch
- Department of Behavioral & Cognitive Biology, University of Vienna, Vienna, Austria
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23
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Ksepka DT, Balanoff AM, Smith NA, Bever GS, Bhullar BAS, Bourdon E, Braun EL, Burleigh JG, Clarke JA, Colbert MW, Corfield JR, Degrange FJ, De Pietri VL, Early CM, Field DJ, Gignac PM, Gold MEL, Kimball RT, Kawabe S, Lefebvre L, Marugán-Lobón J, Mongle CS, Morhardt A, Norell MA, Ridgely RC, Rothman RS, Scofield RP, Tambussi CP, Torres CR, van Tuinen M, Walsh SA, Watanabe A, Witmer LM, Wright AK, Zanno LE, Jarvis ED, Smaers JB. Tempo and Pattern of Avian Brain Size Evolution. Curr Biol 2020; 30:2026-2036.e3. [DOI: 10.1016/j.cub.2020.03.060] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Revised: 02/05/2020] [Accepted: 03/23/2020] [Indexed: 11/25/2022]
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24
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Rogell B, Dowling DK, Husby A. Controlling for body size leads to inferential biases in the biological sciences. Evol Lett 2019; 4:73-82. [PMID: 32055413 PMCID: PMC7006466 DOI: 10.1002/evl3.151] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2018] [Revised: 10/14/2019] [Accepted: 10/20/2019] [Indexed: 01/15/2023] Open
Abstract
Many traits correlate with body size. Studies that seek to uncover the ecological factors that drive evolutionary responses in traits typically examine these responses relative to associated changes in body size using multiple regression analysis. However, it is not well appreciated that in the presence of strongly correlated variables, the partial (i.e., relative) regression coefficients often change sign compared to the original coefficients. Such sign reversals are difficult to interpret in a biologically meaningful way, and could lead to erroneous evolutionary inferences if the true mechanism underlying the sign reversal differed from the proposed mechanism. Here, we use simulations to demonstrate that sign reversal occurs over a wide range of parameter values common in the biological sciences. Further, as a case‐in‐point, we review the literature on brain size evolution; a field that explores how ecological traits relate to the evolution of relative brain size (brain size relative to body size). We find that most studies show sign reversals and thus that the inferences of many studies in this field may be inconclusive. Finally, we propose some approaches to mitigating this issue.
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Affiliation(s)
- Björn Rogell
- Department of Zoology Stockholm University Svante Arrhenius väg 18 Stockholm Sweden.,Department of Aquatic Resources, Institute of Freshwater Research Swedish University of Agricultural Sciences Drottningholm 17893 Sweden
| | - Damian K Dowling
- School of Biological Sciences Monash University Clayton Victoria 3800 Australia
| | - Arild Husby
- Centre for Biodiversity Dynamics Norwegian University of Science and Technology 7491 Trondheim Norway.,Evolutionary Biology, Department of Ecology and Genetics Uppsala University 75236 Uppsala Sweden
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25
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Font E, García-Roa R, Pincheira-Donoso D, Carazo P. Rethinking the Effects of Body Size on the Study of Brain Size Evolution. BRAIN, BEHAVIOR AND EVOLUTION 2019; 93:182-195. [DOI: 10.1159/000501161] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2018] [Accepted: 05/22/2019] [Indexed: 11/19/2022]
Abstract
Body size correlates with most structural and functional components of an organism’s phenotype – brain size being a prime example of allometric scaling with animal size. Therefore, comparative studies of brain evolution in vertebrates rely on controlling for the scaling effects of body size variation on brain size variation by calculating brain weight/body weight ratios. Differences in the brain size-body size relationship between taxa are usually interpreted as differences in selection acting on the brain or its components, while selection pressures acting on body size, which are among the most prevalent in nature, are rarely acknowledged, leading to conflicting and confusing conclusions. We address these problems by comparing brain-body relationships from across >1,000 species of birds and non-avian reptiles. Relative brain size in birds is often assumed to be 10 times larger than in reptiles of similar body size. We examine how differences in the specific gravity of body tissues and in body design (e.g., presence/absence of a tail or a dense shell) between these two groups can affect estimates of relative brain size. Using phylogenetic comparative analyses, we show that the gap in relative brain size between birds and reptiles has been grossly exaggerated. Our results highlight the need to take into account differences between taxa arising from selection pressures affecting body size and design, and call into question the widespread misconception that reptile brains are small and incapable of supporting sophisticated behavior and cognition.
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26
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Wartel A, Lindenfors P, Lind J. Whatever you want: Inconsistent results are the rule, not the exception, in the study of primate brain evolution. PLoS One 2019; 14:e0218655. [PMID: 31329603 PMCID: PMC6645455 DOI: 10.1371/journal.pone.0218655] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Accepted: 06/06/2019] [Indexed: 01/14/2023] Open
Abstract
Primate brains differ in size and architecture. Hypotheses to explain this variation are numerous and many tests have been carried out. However, after body size has been accounted for there is little left to explain. The proposed explanatory variables for the residual variation are many and covary, both with each other and with body size. Further, the data sets used in analyses have been small, especially in light of the many proposed predictors. Here we report the complete list of models that results from exhaustively combining six commonly used predictors of brain and neocortex size. This provides an overview of how the output from standard statistical analyses changes when the inclusion of different predictors is altered. By using both the most commonly tested brain data set and the inclusion of new data we show that the choice of included variables fundamentally changes the conclusions as to what drives primate brain evolution. Our analyses thus reveal why studies have had troubles replicating earlier results and instead have come to such different conclusions. Although our results are somewhat disheartening, they highlight the importance of scientific rigor when trying to answer difficult questions. It is our position that there is currently no empirical justification to highlight any particular hypotheses, of those adaptive hypotheses we have examined here, as the main determinant of primate brain evolution.
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Affiliation(s)
- Andreas Wartel
- Centre for Cultural Evolution and Department of Zoology Stockholm University, Stockholm, Sweden
| | - Patrik Lindenfors
- Centre for Cultural Evolution and Department of Zoology Stockholm University, Stockholm, Sweden
- Institute for Future Studies, Stockholm, Sweden
| | - Johan Lind
- Centre for Cultural Evolution and Department of Zoology Stockholm University, Stockholm, Sweden
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27
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Affiliation(s)
- Joseph Robert Burger
- Department of Biology, University of North Carolina, Chapel Hill, NC, USA
- North Carolina Museum of Natural Sciences, Raleigh, NC, USA
| | | | - Claire Leadbetter
- Department of Biology, University of North Carolina, Chapel Hill, NC, USA
| | - Farhin Shaikh
- Department of Biology, University of North Carolina, Chapel Hill, NC, USA
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Hofman MA. On the nature and evolution of the human mind. PROGRESS IN BRAIN RESEARCH 2019; 250:251-283. [DOI: 10.1016/bs.pbr.2019.03.016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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29
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Ocampo D, Barrantes G, Uy JAC. Morphological adaptations for relatively larger brains in hummingbird skulls. Ecol Evol 2018; 8:10482-10488. [PMID: 30464820 PMCID: PMC6238128 DOI: 10.1002/ece3.4513] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Revised: 08/12/2018] [Accepted: 08/17/2018] [Indexed: 02/03/2023] Open
Abstract
A common allometric pattern called Haller's Rule states that small species have relatively larger brains and eyes than larger species of the same taxonomic group. This pattern imposes drastic structural changes and energetic costs on small species to produce and maintain a disproportionate amount of nervous tissue. Indeed, several studies have shown the significant metabolic costs of having relatively larger brains; however, little is known about the structural constraints and adaptations required for housing these relatively larger brains and eyes. Because hummingbirds include the smallest birds, they are ideal for exploring how small species evolve morphological adaptations for housing relatively larger brain and eyes. We here present results from a comparative study of hummingbirds and show that the smallest species have the lowest levels of ossification, the most compact braincases, and relatively larger eye sockets, but lower eye/head proportion, than larger species. In contrast to Passerines, skull ossification in hummingbirds correlates with body and brain size but not with age. Correlation of these skull traits with body size might represent adaptations to facilitate housing relatively larger brain and eyes, rather than just heterochronic effects related to change in body size. These structural changes in skull traits allow small animals to accommodate disproportionately larger brains and eyes without further increasing overall head size.
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Affiliation(s)
- Diego Ocampo
- Department of BiologyUniversity of MiamiCoral GablesFlorida
- Escuela de BiologíaUniversidad de Costa RicaSan JoséCosta Rica
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30
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Hawkes K, Finlay BL. Mammalian brain development and our grandmothering life history. Physiol Behav 2018; 193:55-68. [DOI: 10.1016/j.physbeh.2018.01.013] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2017] [Revised: 01/15/2018] [Accepted: 01/16/2018] [Indexed: 11/28/2022]
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31
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Navarrete AF, Blezer ELA, Pagnotta M, de Viet ESM, Todorov OS, Lindenfors P, Laland KN, Reader SM. Primate Brain Anatomy: New Volumetric MRI Measurements for Neuroanatomical Studies. BRAIN, BEHAVIOR AND EVOLUTION 2018; 91:109-117. [PMID: 29894995 DOI: 10.1159/000488136] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Accepted: 03/05/2018] [Indexed: 12/20/2022]
Abstract
Since the publication of the primate brain volumetric dataset of Stephan and colleagues in the early 1980s, no major new comparative datasets covering multiple brain regions and a large number of primate species have become available. However, technological and other advances in the last two decades, particularly magnetic resonance imaging (MRI) and the creation of institutions devoted to the collection and preservation of rare brain specimens, provide opportunities to rectify this situation. Here, we present a new dataset including brain region volumetric measurements of 39 species, including 20 species not previously available in the literature, with measurements of 16 brain areas. These volumes were extracted from MRI of 46 brains of 38 species from the Netherlands Institute of Neuroscience Primate Brain Bank, scanned at high resolution with a 9.4-T scanner, plus a further 7 donated MRI of 4 primate species. Partial measurements were made on an additional 8 brains of 5 species. We make the dataset and MRI scans available online in the hope that they will be of value to researchers conducting comparative studies of primate evolution.
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Affiliation(s)
- Ana F Navarrete
- Centre for Social Learning and Cognitive Evolution, School of Biology, University of St. Andrews, St. Andrews, United Kingdom.,Department of Biology and Helmholtz Institute, Utrecht University, Utrecht, the Netherlands
| | - Erwin L A Blezer
- Biomedical MR Imaging and Spectroscopy Group, Center for Image Sciences, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Murillo Pagnotta
- Centre for Social Learning and Cognitive Evolution, School of Biology, University of St. Andrews, St. Andrews, United Kingdom
| | - Elizabeth S M de Viet
- Department of Biology and Helmholtz Institute, Utrecht University, Utrecht, the Netherlands
| | - Orlin S Todorov
- Department of Biology and Helmholtz Institute, Utrecht University, Utrecht, the Netherlands
| | - Patrik Lindenfors
- Institute for Future Studies, Stockholm, Sweden.,Centre for Cultural Evolution & Department of Zoology, Stockholm University, Stockholm, Sweden
| | - Kevin N Laland
- Centre for Social Learning and Cognitive Evolution, School of Biology, University of St. Andrews, St. Andrews, United Kingdom
| | - Simon M Reader
- Department of Biology and Helmholtz Institute, Utrecht University, Utrecht, the Netherlands.,Department of Biology, McGill University, Montreal, Québec, Canada
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32
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McNab BK, Köhler M. The difficulty with correlations: Energy expenditure and brain mass in bats. Comp Biochem Physiol A Mol Integr Physiol 2017; 212:9-14. [DOI: 10.1016/j.cbpa.2017.06.017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Revised: 06/16/2017] [Accepted: 06/16/2017] [Indexed: 10/19/2022]
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33
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Veitschegger K. The effect of body size evolution and ecology on encephalization in cave bears and extant relatives. BMC Evol Biol 2017; 17:124. [PMID: 28583080 PMCID: PMC5460516 DOI: 10.1186/s12862-017-0976-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2017] [Accepted: 05/22/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The evolution of larger brain volumes relative to body size in Mammalia is the subject of an extensive amount of research. Early on palaeontologists were interested in the brain of cave bears, Ursus spelaeus, and described its morphology and size. However, until now, it was not possible to compare the absolute or relative brain size in a phylogenetic context due to the lack of an established phylogeny, comparative material, and phylogenetic comparative methods. In recent years, many tools for comparing traits within phylogenies were developed and the phylogenetic position of cave bears was resolved based on nuclear as well as mtDNA. RESULTS Cave bears exhibit significantly lower encephalization compared to their contemporary relatives and intraspecific brain mass variation remained rather small. Encephalization was correlated with the combined dormancy-diet score. Body size evolution was a main driver in the degree of encephalization in cave bears as it increased in a much higher pace than brain size. In Ursus spelaeus, brain and body size increase over time albeit differently paced. This rate pattern is different in the highest encephalized bear species within the dataset, Ursus malayanus. The brain size in this species increased while body size heavily decreased compared to its ancestral stage. CONCLUSIONS Early on in the evolution of cave bears encephalization decreased making it one of the least encephalized bear species compared to extant and extinct members of Ursidae. The results give reason to suspect that as herbivorous animals, cave bears might have exhibited a physiological buffer strategy to survive the strong seasonality of their environment. Thus, brain size was probably affected by the negative trade-off with adipose tissue as well as diet. The decrease of relative brain size in the herbivorous Ursus spelaeus is the result of a considerable increase in body size possibly in combination with environmental conditions forcing them to rest during winters.
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Affiliation(s)
- Kristof Veitschegger
- Palaeontological Institute and Museum, University of Zurich, Karl Schmid-Strasse 4, 8006, Zürich, Switzerland.
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34
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Sakai ST, Arsznov BM, Hristova AE, Yoon EJ, Lundrigan BL. Big Cat Coalitions: A Comparative Analysis of Regional Brain Volumes in Felidae. Front Neuroanat 2016; 10:99. [PMID: 27812324 PMCID: PMC5071314 DOI: 10.3389/fnana.2016.00099] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Accepted: 09/28/2016] [Indexed: 11/13/2022] Open
Abstract
Broad-based species comparisons across mammalian orders suggest a number of factors that might influence the evolution of large brains. However, the relationship between these factors and total and regional brain size remains unclear. This study investigated the relationship between relative brain size and regional brain volumes and sociality in 13 felid species in hopes of revealing relationships that are not detected in more inclusive comparative studies. In addition, a more detailed analysis was conducted of four focal species: lions (Panthera leo), leopards (Panthera pardus), cougars (Puma concolor), and cheetahs (Acinonyx jubatus). These species differ markedly in sociality and behavioral flexibility, factors hypothesized to contribute to increased relative brain size and/or frontal cortex size. Lions are the only truly social species, living in prides. Although cheetahs are largely solitary, males often form small groups. Both leopards and cougars are solitary. Of the four species, leopards exhibit the most behavioral flexibility, readily adapting to changing circumstances. Regional brain volumes were analyzed using computed tomography. Skulls (n = 75) were scanned to create three-dimensional virtual endocasts, and regional brain volumes were measured using either sulcal or bony landmarks obtained from the endocasts or skulls. Phylogenetic least squares regression analyses found that sociality does not correspond with larger relative brain size in these species. However, the sociality/solitary variable significantly predicted anterior cerebrum (AC) volume, a region that includes frontal cortex. This latter finding is despite the fact that the two social species in our sample, lions and cheetahs, possess the largest and smallest relative AC volumes, respectively. Additionally, an ANOVA comparing regional brain volumes in four focal species revealed that lions and leopards, while not significantly different from one another, have relatively larger AC volumes than are found in cheetahs or cougars. Further, female lions possess a significantly larger AC volume than conspecific males; female lion values were also larger than those of the other three species (regardless of sex). These results may reflect greater complexity in a female lion’s social world, but additional studies are necessary. These data suggest that within family comparisons may reveal variations not easily detected by broad comparative analyses.
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Affiliation(s)
- Sharleen T Sakai
- Department of Psychology, Michigan State University, East LansingMI, USA; Neuroscience Program, Michigan State University, East LansingMI, USA
| | - Bradley M Arsznov
- Department of Psychology, Minnesota State University, Mankato, Mankato MN, USA
| | - Ani E Hristova
- Department of Psychology, Michigan State University, East Lansing MI, USA
| | - Elise J Yoon
- Department of Psychology, Michigan State University, East Lansing MI, USA
| | - Barbara L Lundrigan
- Department of Integrative Biology and Michigan State University Museum, Michigan State University, East Lansing MI, USA
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35
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Henriksen R, Johnsson M, Andersson L, Jensen P, Wright D. The domesticated brain: genetics of brain mass and brain structure in an avian species. Sci Rep 2016; 6:34031. [PMID: 27687864 PMCID: PMC5043184 DOI: 10.1038/srep34031] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Accepted: 09/05/2016] [Indexed: 11/08/2022] Open
Abstract
As brain size usually increases with body size it has been assumed that the two are tightly constrained and evolutionary studies have therefore often been based on relative brain size (i.e. brain size proportional to body size) rather than absolute brain size. The process of domestication offers an excellent opportunity to disentangle the linkage between body and brain mass due to the extreme selection for increased body mass that has occurred. By breeding an intercross between domestic chicken and their wild progenitor, we address this relationship by simultaneously mapping the genes that control inter-population variation in brain mass and body mass. Loci controlling variation in brain mass and body mass have separate genetic architectures and are therefore not directly constrained. Genetic mapping of brain regions indicates that domestication has led to a larger body mass and to a lesser extent a larger absolute brain mass in chickens, mainly due to enlargement of the cerebellum. Domestication has traditionally been linked to brain mass regression, based on measurements of relative brain mass, which confounds the large body mass augmentation due to domestication. Our results refute this concept in the chicken.
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Affiliation(s)
- R. Henriksen
- AVIAN Behavioural Genomics and Physiology Group, IFM Biology, Linköping University, Linköping 58183, Sweden
| | - M. Johnsson
- AVIAN Behavioural Genomics and Physiology Group, IFM Biology, Linköping University, Linköping 58183, Sweden
| | - L. Andersson
- Dept of Medical Biochemistry and Microbiology, Uppsala University, BMC, Husargatan 3, Uppsala 75123, Sweden
| | - P. Jensen
- AVIAN Behavioural Genomics and Physiology Group, IFM Biology, Linköping University, Linköping 58183, Sweden
| | - D. Wright
- AVIAN Behavioural Genomics and Physiology Group, IFM Biology, Linköping University, Linköping 58183, Sweden
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36
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Halley AC. Prenatal Brain-Body Allometry in Mammals. BRAIN, BEHAVIOR AND EVOLUTION 2016; 88:14-24. [DOI: 10.1159/000447254] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 05/30/2016] [Indexed: 11/19/2022]
Abstract
Variation in relative brain size among adult mammals is produced by different patterns of brain and body growth across ontogeny. Fetal development plays a central role in generating this diversity, and aspects of prenatal physiology such as maternal relative metabolic rate, altriciality, and placental morphology have been proposed to explain allometric differences in neonates and adults. Primates are also uniquely encephalized across fetal development, but it remains unclear when this pattern emerges during development and whether it is common to all primate radiations. To reexamine these questions across a wider range of mammalian radiations, data on the primarily fetal rapid growth phase (RGP) of ontogenetic brain-body allometry was compiled for diverse primate (np = 12) and nonprimate (nnp = 16) mammalian species, and was complemented by later ontogenetic data in 16 additional species (np = 9; nnp = 7) as well as neonatal proportions in a much larger sample (np = 38; nnp = 83). Relative BMR, litter size, altriciality, and placental morphology fail to predict RGP slopes as would be expected if physiological and life history variables constrained fetal brain growth, but are associated with differences in birth timing along allometric trajectories. Prenatal encephalization is shared by all primate radiations, is unique to the primate Order, and is characterized by: (1) a robust change in early embryonic brain/body proportions, and (2) higher average RGP allometric slopes due to slower fetal body growth. While high slopes are observed in several nonprimate species, primates alone exhibit an intercept shift at 1 g body size. This suggests that primate prenatal encephalization is a consequence of early changes to embryonic neural and somatic tissue growth in primates that remain poorly understood.
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37
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Tsuboi M, Kotrschal A, Hayward A, Buechel SD, Zidar J, Løvlie H, Kolm N. Evolution of brain-body allometry in Lake Tanganyika cichlids. Evolution 2016; 70:1559-68. [DOI: 10.1111/evo.12965] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Revised: 05/12/2016] [Accepted: 05/18/2016] [Indexed: 11/30/2022]
Affiliation(s)
- Masahito Tsuboi
- Evolutionary Biology Centre; Department of Ecology and Genetics/Animal Ecology; Uppsala University; Norbyvägen 18D SE-75236 Uppsala Sweden
| | - Alexander Kotrschal
- Department of Zoology/Ethology; Stockholm University; Svante Arrhenius väg 18B SE-10691 Stockholm Sweden
| | - Alexander Hayward
- Department of Zoology/Ethology; Stockholm University; Svante Arrhenius väg 18B SE-10691 Stockholm Sweden
| | - Severine Denise Buechel
- Department of Zoology/Ethology; Stockholm University; Svante Arrhenius väg 18B SE-10691 Stockholm Sweden
| | - Josefina Zidar
- IFM Biology; Linköping University; Campus Valla SE-58183 Linköping Sweden
| | - Hanne Løvlie
- IFM Biology; Linköping University; Campus Valla SE-58183 Linköping Sweden
| | - Niclas Kolm
- Department of Zoology/Ethology; Stockholm University; Svante Arrhenius väg 18B SE-10691 Stockholm Sweden
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38
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Gignac P, O'Brien H. Suchian Feeding Success at the Interface of Ontogeny and Macroevolution. Integr Comp Biol 2016; 56:449-58. [PMID: 27252224 PMCID: PMC4990708 DOI: 10.1093/icb/icw041] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
There have been a number of attempts to explain how crocodylian bite-force performance covaries with cranial form and diet. However, the mechanics and morphologies of crocodylian jaws have thus far remained incongruent with data on their performance and evolution. For example, it is largely assumed that the functional anatomy and performance of adults tightly fits the adult niche. At odds with this precept are groups with resource-dependent growth, whose juvenile stages undergo shifts in mass, morphology, and resource usage to overcome strong selection related to issues of small body size, as compared to adults. Crocodylians are an example of such a group. As living suchians, they also have a long and fossil-rich evolutionary history, characterized by analogous increases in body size, diversifications in rostrodental form, and shifts in diet. Here we use biomechanical and evolutionary modeling techniques to study the development and evolution of the suchian feeding apparatus and to formally assess the impact of potential ontogenetic-evolutionary parallels on clade dynamics. We show that patterns of ontogenetic and evolutionary bite-force changes exhibit inverted patterns of heterochrony, indicating that early ontogenetic trends are established as macroevolutionary patterns within Neosuchia, prior to the origin of Eusuchia. Although selection can act on any life-history stage, our findings suggest that selection on neonates and juveniles, in particular, can contribute to functionally important morphologies that aid individual and clade success without being strongly tied to their adult niche.
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Affiliation(s)
- Paul Gignac
- *Department of Anatomy and Cell Biology, Oklahoma State University Center for Health Sciences, Tulsa, Oklahoma 74107-1898, USA
| | - Haley O'Brien
- *Department of Anatomy and Cell Biology, Oklahoma State University Center for Health Sciences, Tulsa, Oklahoma 74107-1898, USA Department of Biological Sciences (Graduate Program in Ecology and Evolutionary Biology), Ohio University, Athens, Ohio 45701, USA
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39
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Marugán-Lobón J, Watanabe A, Kawabe S. Studying avian encephalization with geometric morphometrics. J Anat 2016; 229:191-203. [PMID: 27112986 DOI: 10.1111/joa.12476] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/02/2016] [Indexed: 02/02/2023] Open
Abstract
Encephalization is a core concept in comparative neurobiology, aiming to quantify the neurological capacity of organisms. For measuring encephalization, many studies have employed relative brain sizes corrected for expected allometric scaling to body size. Here we highlight the utility of a multivariate geometric morphometric (GM) approach for visualizing and analyzing neuroanatomical shape variation associated with encephalization. GM readily allows the statistical evaluation of covariates, such as size, and many software tools exist for visualizing their effects on shape. Thus far, however, studies using GM have not attempted to translate the meaning of encephalization to shape data. As such, we tested the statistical relationship between size and encephalization quotients (EQs) to brain shape utilizing a broad interspecific sample of avian endocranial data. Although statistically significant, the analyses indicate that allometry accounts for <10% of total neuroanatomical shape variation. Notably, we find that EQs, despite being corrected for allometric scaling based on size, contain size-related neuroanatomical shape changes. In addition, much of what is traditionally considered encephalization comprises clade-specific trends in relative forebrain expansion, particularly driven by landbirds. EQs, therefore, fail to capture 90% of the total neuroanatomical variation after correcting for allometry and shared phylogenetic history. Moving forward, GM techniques provide crucial tools for investigating key drivers of this vast, largely unexplored aspect of avian brain morphology.
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Affiliation(s)
- Jesús Marugán-Lobón
- Unidad de Paleontología, Departamento de Biología, Universidad Autónoma de Madrid, Madrid, Spain.,Dinosaur Institute, Natural History Museum of Los Angeles County, Los Angeles, CA, USA
| | - Akinobu Watanabe
- Division of Paleontology, American Museum of Natural History, New York, NY, USA.,Richard Gilder Graduate School, American Museum of Natural History, New York, NY, USA
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40
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Soligo C, Smaers JB. Contextualising primate origins--an ecomorphological framework. J Anat 2016; 228:608-29. [PMID: 26830706 PMCID: PMC4804135 DOI: 10.1111/joa.12441] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/16/2015] [Indexed: 12/15/2022] Open
Abstract
Ecomorphology - the characterisation of the adaptive relationship between an organism's morphology and its ecological role - has long been central to theories of the origin and early evolution of the primate order. This is exemplified by two of the most influential theories of primate origins: Matt Cartmill's Visual Predation Hypothesis, and Bob Sussman's Angiosperm Co-Evolution Hypothesis. However, the study of primate origins is constrained by the absence of data directly documenting the events under investigation, and has to rely instead on a fragmentary fossil record and the methodological assumptions inherent in phylogenetic comparative analyses of extant species. These constraints introduce particular challenges for inferring the ecomorphology of primate origins, as morphology and environmental context must first be inferred before the relationship between the two can be considered. Fossils can be integrated in comparative analyses and observations of extant model species and laboratory experiments of form-function relationships are critical for the functional interpretation of the morphology of extinct species. Recent developments have led to important advancements, including phylogenetic comparative methods based on more realistic models of evolution, and improved methods for the inference of clade divergence times, as well as an improved fossil record. This contribution will review current perspectives on the origin and early evolution of primates, paying particular attention to their phylogenetic (including cladistic relationships and character evolution) and environmental (including chronology, geography, and physical environments) contextualisation, before attempting an up-to-date ecomorphological synthesis of primate origins.
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Affiliation(s)
| | - Jeroen B Smaers
- Department of Anthropology, Stony Brook University, Stony Brook, NY, USA
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41
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Grabowski M. Bigger Brains Led to Bigger Bodies?: The Correlated Evolution of Human Brain and Body Size. CURRENT ANTHROPOLOGY 2016. [DOI: 10.1086/685655] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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42
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Abstract
Primates constitute one of the most diverse mammalian clades, and a notable feature of their diversification is the evolution of brain morphology. However, the evolutionary processes and ecological factors behind these changes are largely unknown. In this work, we investigate brain shape diversification of New World monkeys during their adaptive radiation in relation to different ecological dimensions. Our results reveal that brain diversification in this clade can be explained by invoking a model of adaptive peak shifts to unique and shared optima, defined by a multidimensional ecological niche hypothesis. Particularly, we show that the evolution of convergent brain phenotypes may be related to ecological factors associated with group size (e.g., social complexity). Together, our results highlight the complexity of brain evolution and the ecological significance of brain shape changes during the evolutionary diversification of a primate clade.
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43
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Griffin RH, Yapuncich GS. The Independent Evolution Method Is Not a Viable Phylogenetic Comparative Method. PLoS One 2015; 10:e0144147. [PMID: 26683838 PMCID: PMC4687617 DOI: 10.1371/journal.pone.0144147] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2015] [Accepted: 11/11/2015] [Indexed: 11/19/2022] Open
Abstract
Phylogenetic comparative methods (PCMs) use data on species traits and phylogenetic relationships to shed light on evolutionary questions. Recently, Smaers and Vinicius suggested a new PCM, Independent Evolution (IE), which purportedly employs a novel model of evolution based on Felsenstein’s Adaptive Peak Model. The authors found that IE improves upon previous PCMs by producing more accurate estimates of ancestral states, as well as separate estimates of evolutionary rates for each branch of a phylogenetic tree. Here, we document substantial theoretical and computational issues with IE. When data are simulated under a simple Brownian motion model of evolution, IE produces severely biased estimates of ancestral states and changes along individual branches. We show that these branch-specific changes are essentially ancestor-descendant or “directional” contrasts, and draw parallels between IE and previous PCMs such as “minimum evolution”. Additionally, while comparisons of branch-specific changes between variables have been interpreted as reflecting the relative strength of selection on those traits, we demonstrate through simulations that regressing IE estimated branch-specific changes against one another gives a biased estimate of the scaling relationship between these variables, and provides no advantages or insights beyond established PCMs such as phylogenetically independent contrasts. In light of our findings, we discuss the results of previous papers that employed IE. We conclude that Independent Evolution is not a viable PCM, and should not be used in comparative analyses.
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Affiliation(s)
- Randi H. Griffin
- Department of Evolutionary Anthropology, Duke University, Durham, North Carolina, United States of America
- * E-mail: (RHG); (GSY)
| | - Gabriel S. Yapuncich
- Department of Evolutionary Anthropology, Duke University, Durham, North Carolina, United States of America
- * E-mail: (RHG); (GSY)
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44
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Abstract
The world of primate genomics is expanding rapidly in new and exciting ways owing to lowered costs and new technologies in molecular methods and bioinformatics. The primate order is composed of 78 genera and 478 species, including human. Taxonomic inferences are complex and likely a consequence of ongoing hybridization, introgression, and reticulate evolution among closely related taxa. Recently, we applied large-scale sequencing methods and extensive taxon sampling to generate a highly resolved phylogeny that affirms, reforms, and extends previous depictions of primate speciation. The next stage of research uses this phylogeny as a foundation for investigating genome content, structure, and evolution across primates. Ongoing and future applications of a robust primate phylogeny are discussed, highlighting advancements in adaptive evolution of genes and genomes, taxonomy and conservation management of endangered species, next-generation genomic technologies, and biomedicine.
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Affiliation(s)
- Jill Pecon-Slattery
- Laboratory of Genomic Diversity, National Cancer Institute, Frederick, Maryland 21702; Current Affiliation: Smithsonian Conservation Biology Institute, National Zoological Park, Front Royal, Virginia 22630;
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45
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MacDonald K, Smaers JB, Steele J. Hominin geographical range dynamics and relative brain size: Do non-human primates provide a good analogy? J Hum Evol 2015; 87:66-77. [PMID: 26077889 DOI: 10.1016/j.jhevol.2015.05.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2013] [Revised: 05/12/2015] [Accepted: 05/17/2015] [Indexed: 11/15/2022]
Abstract
We use climatic and satellite remote sensing data to characterize environmental seasonality in the geographical ranges of extant non-human primates in order to assess the effect of relative brain size on tolerance of more seasonal habitats. Demonstration of such an effect in living non-human primates could provide a comparative framework for modeling hominin dispersals and geographical range dynamics in the Pliocene and Pleistocene. Our analyses found no such effect: there are neither positive nor negative correlations between relative brain size and either geographical range size or the average and range of values for environmental seasonality, whether analysed at the level of all primates, or within parvorders (strepsirrhine, catarrhine, platyrrhine). Independent analyses by other researchers comparing feeding behaviour and ecology at individual primate study sites demonstrate that in seasonal environments, the year-round metabolic costs of maintaining a relatively large brain are met by adaptive behavioural/dietary strategies. However, consistent with our own results, those comparative studies found that there was no overall association, whether positive or negative, between 'raw' environmental seasonality and primate relative brain size. We must therefore look elsewhere for a comparative model of hominin geographical range dynamics in the Pleistocene.
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Affiliation(s)
- Katharine MacDonald
- Faculty of Archaeology, University of Leiden, Postbus 9515, 2300 RA Leiden, The Netherlands.
| | | | - James Steele
- Institute of Archaeology, University College London, UK; SGAES, University of the Witwatersrand, South Africa
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Weisbecker V, Blomberg S, Goldizen AW, Brown M, Fisher D. The evolution of relative brain size in marsupials is energetically constrained but not driven by behavioral complexity. BRAIN, BEHAVIOR AND EVOLUTION 2015; 85:125-35. [PMID: 25966967 DOI: 10.1159/000377666] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Accepted: 02/02/2015] [Indexed: 11/19/2022]
Abstract
Evolutionary increases in mammalian brain size relative to body size are energetically costly but are also thought to confer selective advantages by permitting the evolution of cognitively complex behaviors. However, many suggested associations between brain size and specific behaviors - particularly related to social complexity - are possibly confounded by the reproductive diversity of placental mammals, whose brain size evolution is the most frequently studied. Based on a phylogenetic generalized least squares analysis of a data set on the reproductively homogenous clade of marsupials, we provide the first quantitative comparison of two hypotheses based on energetic constraints (maternal investment and seasonality) with two hypotheses that posit behavioral selection on relative brain size (social complexity and environmental interactions). We show that the two behavioral hypotheses have far less support than the constraint hypotheses. The only unambiguous associates of brain size are the constraint variables of litter size and seasonality. We also found no association between brain size and specific behavioral complexity categories within kangaroos, dasyurids, and possums. The largest-brained marsupials after phylogenetic correction are from low-seasonality New Guinea, supporting the notion that low seasonality represents greater nutrition safety for brain maintenance. Alternatively, low seasonality might improve the maternal support of offspring brain growth. The lack of behavioral brain size associates, found here and elsewhere, supports the general 'cognitive buffer hypothesis' as the best explanatory framework of mammalian brain size evolution. However, it is possible that brain size alone simply does not provide sufficient resolution on the question of how brain morphology and cognitive capacities coevolve.
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Affiliation(s)
- Vera Weisbecker
- School of Biological Sciences, University of Queensland, St. Lucia, Qld., Australia
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Goswami A, Smaers JB, Soligo C, Polly PD. The macroevolutionary consequences of phenotypic integration: from development to deep time. Philos Trans R Soc Lond B Biol Sci 2015; 369:20130254. [PMID: 25002699 PMCID: PMC4084539 DOI: 10.1098/rstb.2013.0254] [Citation(s) in RCA: 223] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Phenotypic integration is a pervasive characteristic of organisms. Numerous analyses have demonstrated that patterns of phenotypic integration are conserved across large clades, but that significant variation also exists. For example, heterochronic shifts related to different mammalian reproductive strategies are reflected in postcranial skeletal integration and in coordination of bone ossification. Phenotypic integration and modularity have been hypothesized to shape morphological evolution, and we extended simulations to confirm that trait integration can influence both the trajectory and magnitude of response to selection. We further demonstrate that phenotypic integration can produce both more and less disparate organisms than would be expected under random walk models by repartitioning variance in preferred directions. This effect can also be expected to favour homoplasy and convergent evolution. New empirical analyses of the carnivoran cranium show that rates of evolution, in contrast, are not strongly influenced by phenotypic integration and show little relationship to morphological disparity, suggesting that phenotypic integration may shape the direction of evolutionary change, but not necessarily the speed of it. Nonetheless, phenotypic integration is problematic for morphological clocks and should be incorporated more widely into models that seek to accurately reconstruct both trait and organismal evolution.
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Affiliation(s)
- A Goswami
- Research Department of Genetics, Evolution and Environment, University College London, Gower Street, London WC1E 6BT, UK Department of Earth Sciences, University College London, Gower Street, London WC1E 6BT, UK
| | - J B Smaers
- Research Department of Genetics, Evolution and Environment, University College London, Gower Street, London WC1E 6BT, UK Department of Anthropology, University College London, 14 Taviton Street, London WC1H 0BW, UK Department of Anthropology, Stony Brook University, Circle Road, Stony Brook, NY 11794, USA
| | - C Soligo
- Department of Anthropology, University College London, 14 Taviton Street, London WC1H 0BW, UK
| | - P D Polly
- Department of Geological Sciences, Indiana University, 1001 East 10th Street, Bloomington, IN 47401, USA
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Jones KE, Smaers JB, Goswami A. Impact of the terrestrial-aquatic transition on disparity and rates of evolution in the carnivoran skull. BMC Evol Biol 2015; 15:8. [PMID: 25648618 PMCID: PMC4328284 DOI: 10.1186/s12862-015-0285-5] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Accepted: 01/15/2015] [Indexed: 11/25/2022] Open
Abstract
Background Which factors influence the distribution patterns of morphological diversity among clades? The adaptive radiation model predicts that a clade entering new ecological niche will experience high rates of evolution early in its history, followed by a gradual slowing. Here we measure disparity and rates of evolution in Carnivora, specifically focusing on the terrestrial-aquatic transition in Pinnipedia. We analyze fissiped (mostly terrestrial, arboreal, and semi-arboreal, but also including the semi-aquatic otter) and pinniped (secondarily aquatic) carnivorans as a case study of an extreme ecological transition. We used 3D geometric morphometrics to quantify cranial shape in 151 carnivoran specimens (64 fissiped, 87 pinniped) and five exceptionally-preserved fossil pinnipeds, including the stem-pinniped Enaliarctos emlongi. Range-based and variance-based disparity measures were compared between pinnipeds and fissipeds. To distinguish between evolutionary modes, a Brownian motion model was compared to selective regime shifts associated with the terrestrial-aquatic transition and at the base of Pinnipedia. Further, evolutionary patterns were estimated on individual branches using both Ornstein-Uhlenbeck and Independent Evolution models, to examine the origin of pinniped diversity. Results Pinnipeds exhibit greater cranial disparity than fissipeds, even though they are less taxonomically diverse and, as a clade nested within fissipeds, phylogenetically younger. Despite this, there is no increase in the rate of morphological evolution at the base of Pinnipedia, as would be predicted by an adaptive radiation model, and a Brownian motion model of evolution is supported. Instead basal pinnipeds populated new areas of morphospace via low to moderate rates of evolution in new directions, followed by later bursts within the crown-group, potentially associated with ecological diversification within the marine realm. Conclusion The transition to an aquatic habitat in carnivorans resulted in a shift in cranial morphology without an increase in rate in the stem lineage, contra to the adaptive radiation model. Instead these data suggest a release from evolutionary constraint model, followed by aquatic diversifications within crown families. Electronic supplementary material The online version of this article (doi:10.1186/s12862-015-0285-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Katrina E Jones
- Center for Functional Anatomy and Evolution, Johns Hopkins University, Baltimore, MD, USA. .,Department of Organismic and Evolutionary Biology, Museum of Comparative Zoology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA.
| | - Jeroen B Smaers
- Department of Anthropology, Stony Brook University, Stony Brook, New York, NY, 11794-4364, USA.
| | - Anjali Goswami
- Department of Genetics, Evolution & Environment, University College London, Gower Street, London, WC1E 6BT, UK. .,Department of Earth Sciences, University College London, Gower Street, London, WC1E 6BT, UK.
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The mating brain: early maturing sneaker males maintain investment into the brain also under fast body growth in Atlantic salmon ( Salmo salar). Evol Ecol 2014; 28:1043-1055. [PMID: 26069390 PMCID: PMC4459551 DOI: 10.1007/s10682-014-9715-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Accepted: 05/19/2014] [Indexed: 11/20/2022]
Abstract
It has been suggested that mating behaviours require high levels of cognitive ability. However, since investment into mating and the brain both are costly features, their relationship is likely characterized by energetic trade-offs. Empirical data on the subject remains equivocal. We investigated if early sexual maturation was associated with brain development in Atlantic salmon (Salmo salar), in which males can either stay in the river and sexually mature at a small size (sneaker males) or migrate to the sea and delay sexual maturation until they have grown much larger (anadromous males). Specifically, we tested how sexual maturation may induce plastic changes in brain development by rearing juveniles on either natural or ad libitum feeding levels. After their first season we compared brain size and brain region volumes across both types of male mating tactics and females. Body growth increased greatly across both male mating tactics and females during ad libitum feeding as compared to natural feeding levels. However, despite similar relative increases in body size, early maturing sneaker males maintained larger relative brain size during ad libitum feeding levels as compared to anadromous males and females. We also detected several differences in the relative size of separate brain regions across feeding treatments, sexes and mating strategies. For instance, the relative size of the cognitive centre of the brain, the telencephalon, was largest in sneaker males. Our data support that a large relative brain size is maintained in individuals that start reproduction early also during fast body growth. We propose that the cognitive demands during complex mating behaviours maintain a high level of investment into brain development in reproducing individuals.
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Shine JM, Shine R. Delegation to automaticity: the driving force for cognitive evolution? Front Neurosci 2014; 8:90. [PMID: 24808820 PMCID: PMC4010745 DOI: 10.3389/fnins.2014.00090] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2014] [Accepted: 04/09/2014] [Indexed: 11/30/2022] Open
Abstract
The ability to delegate control over repetitive tasks from higher to lower neural centers may be a fundamental innovation in human cognition. Plausibly, the massive neurocomputational challenges associated with the mastery of balance during the evolution of bipedality in proto-humans provided a strong selective advantage to individuals with brains capable of efficiently transferring tasks in this way. Thus, the shift from quadrupedal to bipedal locomotion may have driven the rapid evolution of distinctive features of human neuronal functioning. We review recent studies of functional neuroanatomy that bear upon this hypothesis, and identify ways to test our ideas.
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Affiliation(s)
- J. M. Shine
- Brain and Mind Research Institute, The University of SydneySydney, NSW, Australia
| | - R. Shine
- School of Biological Sciences, The University of SydneySydney, NSW, Australia
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