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Speechley EM, Ashton BJ, Foo YZ, Simmons LW, Ridley AR. Meta-analyses reveal support for the Social Intelligence Hypothesis. Biol Rev Camb Philos Soc 2024. [PMID: 38855980 DOI: 10.1111/brv.13103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Revised: 05/13/2024] [Accepted: 05/15/2024] [Indexed: 06/11/2024]
Abstract
The Social Intelligence Hypothesis (SIH) is one of the leading explanations for the evolution of cognition. Since its inception a vast body of literature investigating the predictions of the SIH has accumulated, using a variety of methodologies and species. However, the generalisability of the hypothesis remains unclear. To gain an understanding of the robustness of the SIH as an explanation for the evolution of cognition, we systematically searched the literature for studies investigating the predictions of the SIH. Accordingly, we compiled 103 studies with 584 effect sizes from 17 taxonomic orders. We present the results of four meta-analyses which reveal support for the SIH across interspecific, intraspecific and developmental studies. However, effect sizes did not differ significantly between the cognitive or sociality metrics used, taxonomy or testing conditions. Thus, support for the SIH is similar across studies using neuroanatomy and cognitive performance, those using broad categories of sociality, group size and social interactions, across taxonomic groups, and for tests conducted in captivity or the wild. Overall, our meta-analyses support the SIH as an evolutionary and developmental explanation for cognitive variation.
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Affiliation(s)
- Elizabeth M Speechley
- Centre for Evolutionary Biology, University of Western Australia, 35 Stirling Highway, Perth, WA, 6009, Australia
| | - Benjamin J Ashton
- Centre for Evolutionary Biology, University of Western Australia, 35 Stirling Highway, Perth, WA, 6009, Australia
- School of Natural Sciences, Macquarie University, 205b Culloden Road, Sydney, NSW, 2109, Australia
| | - Yong Zhi Foo
- Centre for Evolutionary Biology, University of Western Australia, 35 Stirling Highway, Perth, WA, 6009, Australia
| | - Leigh W Simmons
- Centre for Evolutionary Biology, University of Western Australia, 35 Stirling Highway, Perth, WA, 6009, Australia
| | - Amanda R Ridley
- Centre for Evolutionary Biology, University of Western Australia, 35 Stirling Highway, Perth, WA, 6009, Australia
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2
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Button DJ, Zanno LE. Neuroanatomy of the late Cretaceous Thescelosaurus neglectus (Neornithischia: Thescelosauridae) reveals novel ecological specialisations within Dinosauria. Sci Rep 2023; 13:19224. [PMID: 37932280 PMCID: PMC10628235 DOI: 10.1038/s41598-023-45658-3] [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: 06/06/2023] [Accepted: 10/22/2023] [Indexed: 11/08/2023] Open
Abstract
Ornithischian dinosaurs exhibited a diversity of ecologies, locomotory modes, and social structures, making them an ideal clade in which to study the evolution of neuroanatomy and behaviour. Here, we present a 3D digital reconstruction of the endocranial spaces of the latest Cretaceous neornithischian Thescelosaurus neglectus, in order to interpret the neuroanatomy and paleobiology of one of the last surviving non-avian dinosaurs. Results demonstrate that the brain of Thescelosaurus was relatively small compared to most other neornithischians, instead suggesting cognitive capabilities within the range of extant reptiles. Other traits include a narrow hearing range, with limited ability to distinguish high frequencies, paired with unusually well-developed olfactory lobes and anterior semicircular canals, indicating acute olfaction and vestibular sensitivity. This character combination, in conjunction with features of the postcranial anatomy, is consistent with specializations for burrowing behaviours in the clade, as evidenced by trace and skeletal fossil evidence in earlier-diverging thescelosaurids, although whether they reflect ecological adaptations or phylogenetic inheritance in T. neglectus itself is unclear. Nonetheless, our results provide the first evidence of neurological specializations to burrowing identified within Ornithischia, and non-avian dinosaurs more generally, expanding the range of ecological adaptations recognized within this major clade.
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Affiliation(s)
- David J Button
- Bristol Palaeobiology Group, School of Earth Sciences, University of Bristol, Bristol, BS8 1TQ, UK.
| | - Lindsay E Zanno
- Paleontology, North Carolina Museum of Natural Sciences, Raleigh, NC, USA
- Department of Biological Sciences, North Carolina State University, Raleigh, NC, USA
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3
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Clear E, Grant R, Gardiner J, Brassey C. Baculum shape complexity correlates to metrics of post-copulatory sexual selection in Musteloidea. J Morphol 2023; 284:e21572. [PMID: 36806148 PMCID: PMC10952176 DOI: 10.1002/jmor.21572] [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: 10/13/2022] [Revised: 02/14/2023] [Accepted: 02/18/2023] [Indexed: 02/22/2023]
Abstract
The penis bone, or baculum, is present in many orders of mammals, although its function is still relatively unknown, mainly due to the challenges with studying the baculum in vivo. Suggested functions include increasing vaginal friction, prolonging intromission and inducing ovulation. Since it is difficult to study baculum function directly, functional morphology can give important insights. Shape complexity techniques, in particular, are likely to offer a useful metric of baculum morphology, especially since finding homologous landmarks on such a structure is challenging. This study focuses on measuring baculum shape complexity in the Musteloidea-a large superfamily spanning a range of body sizes with well-developed, qualitatively diverse bacula. We compared two shape complexity metrics-alpha shapes and ariaDNE and conducted analyses over a range of six different coefficients, or bandwidths, in 32 species of Musteloidea. Overall, we found that shape complexity, especially at the baculum distal tip, is associated with intromission duration using both metrics. These complexities can include hooks, bifurcations and other additional projections. In addition, alpha shapes complexity was also associated with relative testes mass. These results suggest that post-copulatory mechanisms of sexual selection are probably driving the evolution of more complex-shaped bacula tips in Musteloidea and are likely to be especially involved in increasing intromission duration during copulation.
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Affiliation(s)
- Emma Clear
- Faculty of Science and EngineeringManchester Metropolitan UniversityManchesterUK
| | - Robyn Grant
- Faculty of Science and EngineeringManchester Metropolitan UniversityManchesterUK
| | - James Gardiner
- Institute of Life Course and Medical SciencesThe University of LiverpoolLiverpoolUK
| | - Charlotte Brassey
- Faculty of Science and EngineeringManchester Metropolitan UniversityManchesterUK
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4
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Abstract
Large brains provide adaptive cognitive benefits but require unusually high, near-constant energy inputs and become fully functional well after their growth is completed. Consequently, young of most larger-brained endotherms should not be able to independently support the growth and development of their own brains. This paradox is solved if the evolution of extended parental provisioning facilitated brain size evolution. Comparative studies indeed show that extended parental provisioning coevolved with brain size and that it may improve immature survival. The major role of extended parental provisioning supports the idea that the ability to sustain the costs of brains limited brain size evolution.
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5
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De Meester G, Van Linden L, Torfs J, Pafilis P, Šunje E, Steenssens D, Zulčić T, Sassalos A, Van Damme R. Learning with lacertids: Studying the link between ecology and cognition within a comparative framework. Evolution 2022; 76:2531-2552. [PMID: 36111365 DOI: 10.1111/evo.14618] [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: 04/03/2022] [Revised: 08/10/2022] [Accepted: 08/21/2022] [Indexed: 01/22/2023]
Abstract
Cognition is an essential tool for animals to deal with environmental challenges. Nonetheless, the ecological forces driving the evolution of cognition throughout the animal kingdom remain enigmatic. Large-scale comparative studies on multiple species and cognitive traits have been advanced as the best way to facilitate our understanding of cognitive evolution, but such studies are rare. Here, we tested 13 species of lacertid lizards (Reptilia: Lacertidae) using a battery of cognitive tests measuring inhibitory control, problem-solving, and spatial and reversal learning. Next, we tested the relationship between species' performance and (a) resource availability (temperature and precipitation), habitat complexity (Normalized Difference Vegetation Index), and habitat variability (seasonality) in their natural habitat and (b) their life history (size at hatching and maturity, clutch size, and frequency). Although species differed markedly in their cognitive abilities, such variation was mostly unrelated to their ecology and life history. Yet, species living in more variable environments exhibited lower behavioral flexibility, likely due to energetic constrains in such habitats. Our standardized protocols provide opportunities for collaborative research, allowing increased sample sizes and replication, essential for moving forward in the field of comparative cognition. Follow-up studies could include more detailed measures of habitat structure and look at other potential selective drivers such as predation.
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Affiliation(s)
- Gilles De Meester
- Functional Morphology Lab, Department of Biology, University of Antwerp, Wilrijk, 2610, Belgium.,Section of Zoology and Marine Biology, Department of Biology, National and Kapodistrian University of Athens, Athens, 157 84, Greece
| | - Lisa Van Linden
- Functional Morphology Lab, Department of Biology, University of Antwerp, Wilrijk, 2610, Belgium
| | - Jonas Torfs
- Functional Morphology Lab, Department of Biology, University of Antwerp, Wilrijk, 2610, Belgium
| | - Panayiotis Pafilis
- Section of Zoology and Marine Biology, Department of Biology, National and Kapodistrian University of Athens, Athens, 157 84, Greece
| | - Emina Šunje
- Functional Morphology Lab, Department of Biology, University of Antwerp, Wilrijk, 2610, Belgium.,Department of Biology, Faculty of Natural Sciences, University of Sarajevo, Sarajevo, 71000, Bosnia and Herzegovina.,Herpetological Association in Bosnia and Herzegovina: BHHU: ATRA, Sarajevo, 71000, Bosnia and Herzegovina
| | - Dries Steenssens
- Functional Morphology Lab, Department of Biology, University of Antwerp, Wilrijk, 2610, Belgium
| | - Tea Zulčić
- Herpetological Association in Bosnia and Herzegovina: BHHU: ATRA, Sarajevo, 71000, Bosnia and Herzegovina
| | - Athanasios Sassalos
- Section of Zoology and Marine Biology, Department of Biology, National and Kapodistrian University of Athens, Athens, 157 84, Greece
| | - Raoul Van Damme
- Functional Morphology Lab, Department of Biology, University of Antwerp, Wilrijk, 2610, Belgium
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6
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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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7
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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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8
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Down a Rabbit Hole: Burrowing Behaviour and Larger Home Ranges are Related to Larger Brains in Leporids. J MAMM EVOL 2022. [DOI: 10.1007/s10914-022-09624-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
Abstract
AbstractStudies on the evolution of brain size variation usually focus on large clades encompassing broad phylogenetic groups. This risks introducing ‘noise’ in the results, often obscuring effects that might be detected in less inclusive clades. Here, we focus on a sample of endocranial volumes (endocasts) of 18 species of rabbits and hares (Lagomorpha: Leporidae), which are a discrete radiation of mammals with a suitably large range of body sizes. Using 60 individuals, we test five popular hypotheses on brain size and olfactory bulb evolution in mammals. We also address the pervasive issue of missing data, using multiple phylogenetic imputations as to conserve the full sample size for all analyses. Our analyses show that home range and burrowing behaviour are the only predictors of leporid brain size variation. Litter size, which is one of the most widely reported constraints on brain size, was unexpectedly not associated with brain size. However, a constraining effect may be masked by a strong association of litter size with temperature seasonality, warranting further study. Lastly, we show that unreasonable estimations of phylogenetic signal (Pagel’s lamba) warrant additional caution when using small sample sizes, such as ours, in comparative studies.
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9
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Axelrod CJ, Robinson BW, Laberge F. Evolutionary divergence in phenotypic plasticity shapes brain size variation between coexisting sunfish ecotypes. J Evol Biol 2022; 35:1363-1377. [PMID: 36073994 DOI: 10.1111/jeb.14085] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 06/10/2022] [Accepted: 07/13/2022] [Indexed: 11/29/2022]
Abstract
Mechanisms that generate brain size variation and the consequences of such variation on ecological performance are poorly understood in most natural animal populations. We use a reciprocal-transplant common garden experiment and foraging performance trials to test for brain size plasticity and the functional consequences of brain size variation in Pumpkinseed sunfish (Lepomis gibbosus) ecotypes that have diverged between nearshore littoral and offshore pelagic lake habitats. Different age-classes of wild-caught juveniles from both habitats were exposed for 6 months to treatments that mimicked littoral and pelagic foraging. Plastic responses in oral jaw size suggested that treatments mimicked natural habitat-specific foraging conditions. Plastic brain size responses to foraging manipulations differed between ecotypes, as only pelagic sourced fish showed brain size plasticity. Only pelagic juveniles under 1 year-old expressed this plastic response, suggesting that plastic brain size responses decline with age and so may be irreversible. Finally, larger brain size was associated with enhanced foraging performance on live benthic but not pelagic prey, providing the first experimental evidence of a relationship between brain size and prey-specific foraging performance in fishes. The recent post-glacial origin of these ecotypes suggests that brain size plasticity can rapidly evolve and diverge in fish under contrasting ecological conditions.
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Affiliation(s)
- Caleb J Axelrod
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, Canada
| | - Beren W Robinson
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, Canada
| | - Frédéric Laberge
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, Canada
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10
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Heldstab SA, Isler K, Graber SM, Schuppli C, van Schaik CP. The economics of brain size evolution in vertebrates. Curr Biol 2022; 32:R697-R708. [PMID: 35728555 DOI: 10.1016/j.cub.2022.04.096] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Across the animal kingdom, we see remarkable variation in brain size. This variation has even increased over evolutionary time. Traditionally, studies aiming to explain brain size evolution have looked at the fitness benefits of increased brain size in relation to its increased cognitive performance in the social and/or ecological domain. However, brains are among the most energetically expensive tissues in the body and also require an uninterrupted energy supply. If not compensated, these energetic demands inevitably lead to a reduction in energy allocation to other vital functions. In this review, we summarize how an increasing number of studies show that to fully comprehend brain size evolution and the large variation in brain size across lineages, it is important to look at the economics of brains, including the different pathways through which the high energetic costs of brains can be offset. We further show how numerous studies converge on the conclusion that cognitive abilities can only drive brain size evolution in vertebrate lineages where they result in an improved energy balance through favourable ecological preconditions. Cognitive benefits that do not directly improve the organism's energy balance can only be selectively favoured when they produce such large improvements in reproduction or survival that they outweigh the negative energetic effects of the large brain.
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Affiliation(s)
- Sandra A Heldstab
- Department of Anthropology, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland; Development and Evolution of Cognition Research Group, Max Planck Institute of Animal Behavior, Bücklestrasse 5a, 78467 Konstanz, Germany.
| | - Karin Isler
- Department of Anthropology, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Sereina M Graber
- Department of Anthropology, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Caroline Schuppli
- Department of Anthropology, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland; Development and Evolution of Cognition Research Group, Max Planck Institute of Animal Behavior, Bücklestrasse 5a, 78467 Konstanz, Germany
| | - Carel P van Schaik
- Department of Anthropology, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland; Comparative Socioecology Group, Max Planck Institute of Animal Behavior, Bücklestrasse 5a, 78467 Konstanz, Germany; Department of Evolutionary Biology and Environmental Science, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
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11
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AnimalTraits - a curated animal trait database for body mass, metabolic rate and brain size. Sci Data 2022; 9:265. [PMID: 35654905 PMCID: PMC9163144 DOI: 10.1038/s41597-022-01364-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Accepted: 04/26/2022] [Indexed: 11/23/2022] Open
Abstract
Trait databases have become important resources for large-scale comparative studies in ecology and evolution. Here we introduce the AnimalTraits database, a curated database of body mass, metabolic rate and brain size, in standardised units, for terrestrial animals. The database has broad taxonomic breadth, including tetrapods, arthropods, molluscs and annelids from almost 2000 species and 1000 genera. All data recorded in the database are sourced from their original empirical publication, and the original metrics and measurements are included with each record. This allows for subsequent data transformations as required. We have included rich metadata to allow users to filter the dataset. The additional R scripts we provide will assist researchers with aggregating standardised observations into species-level trait values. Our goals are to provide this resource without restrictions, to keep the AnimalTraits database current, and to grow the number of relevant traits in the future. Measurement(s) | metabolic rate quantification • body mass • brain size | Technology Type(s) | metabolic rate measurement • body mass quantification • brain mass brain volume |
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12
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The Evolution of Brain Size in Ectothermic Tetrapods: Large Brain Mass Trades-Off with Lifespan in Reptiles. Evol Biol 2022. [DOI: 10.1007/s11692-022-09562-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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13
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Bezerra AM, Citeli N, Galvão A, Carvalho-e-Silva SPD. Minimizing the damage: a methodological proposal to remove the brains of anurans and squamates. IHERINGIA. SERIE ZOOLOGIA 2022. [DOI: 10.1590/1678-4766e2022013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Affiliation(s)
| | | | - Ana Galvão
- Universidade Federal do Rio de Janeiro, Brazil
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14
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Collyer ML, Baken EK, Adams DC. A standardized effect size for evaluating and comparing the strength of phylogenetic signal. Methods Ecol Evol 2021. [DOI: 10.1111/2041-210x.13749] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
| | - Erica K. Baken
- Department of Science Chatham University Pittsburgh PA USA
- Department of Ecology, Evolution, and Organismal Biology Iowa State University Ames IA USA
| | - Dean C. Adams
- Department of Ecology, Evolution, and Organismal Biology Iowa State University Ames IA USA
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15
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Crofts SB, Stankowich T. Stabbing Spines: A review of the Biomechanics and Evolution of Defensive Spines. Integr Comp Biol 2021; 61:655-667. [PMID: 34038530 DOI: 10.1093/icb/icab099] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Spines are ubiquitous in both plants and animals, and while most spines were likely originally used for defense, over time many have been modified in a variety of ways. Here we take an integrative approach to review the form, function, and evolution of spines as a defensive strategy in order to make new connections between physical mechanisms and functional behavior. While this review focuses on spines in mammals, we reference and draw ideas from the literature on spines in other taxa, including plants. We begin by exploring the biomechanics of defensive spines, their varied functions, and nondefensive modifications. We pay particular attention to the mechanics involved in passive puncture and the ways organisms have overcome limitations associated with the low energy input. We then focus on the ecological, physiological, and behavioral factors that promote the evolution of spiny defenses, including predator- and habitat-mediated hypotheses. While there is considerable evidence to support both, studies have generally found that (1) defensive spines are usually effective against one class of attacker (e.g., larger predators) but ineffective against or even facilitate predation by others and (2) species that are more visible or exposed to predators are under much stronger selection to evolve defensive spines or some other robust defense. What type of defensive morphology that evolves, however, is less predictable and probably strongly dependent on both the dominant source of predation and the habitat structure of the organism (e.g., arboreal, terrestrial, and fossorial). We then explore traits that often are correlated with defensive spines and armor, potentially forming armor syndromes, suites of traits that evolve together with body armor in a correlated fashion. In mammals, these include aposematic warning coloration, locomotion style, diet, metabolic rate, and relative brain size. Finally, we encourage integration of mechanistic, behavioral, and evolutionary studies of defensive spines and suggest future avenues of research in the biomechanics, evolution, and behavior of spines and spiny organisms.
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Affiliation(s)
| | - Theodore Stankowich
- Department of Biological Sciences, California State University Long Beach, Long Beach, CA, USA
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16
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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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17
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Yao Z, Qi Y, Yue B, Fu J. Brain size variation along altitudinal gradients in the Asiatic Toad ( Bufo gargarizans). Ecol Evol 2021; 11:3015-3027. [PMID: 33841763 PMCID: PMC8019028 DOI: 10.1002/ece3.7192] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Revised: 12/05/2020] [Accepted: 12/21/2020] [Indexed: 11/23/2022] Open
Abstract
Size changes in brain and brain regions along altitudinal gradients provide insight into the trade-off between energetic expenditure and cognitive capacity. We investigated the brain size variations of the Asiatic Toad (Bufo gargarizans) across altitudes from 700 m to 3,200 m. A total of 325 individuals from 11 sites and two transects were sampled. To reduce confounding factors, all sampling sites within each transect were within a maximum distance of 85 km and an altitudinal difference close to 2,000 m. Brains were dissected, and five regions were both measured directly and with 3D CT scan. There is a significant negative correlation between the relative whole-brain volume (to snout-vent length) and altitude. Furthermore, the relative volumes (to whole-brain volume) of optic tectum and cerebellum also decrease along the altitudinal gradients, while the telencephalon increases its relative volume along the gradients. Therefore, our results are mostly consistent with the expensive brain hypothesis and the functional constraint hypothesis. We suggest that most current hypotheses are not mutually exclusive and data supporting one hypothesis are often partially consistent with others. More studies on mechanisms are needed to explain the brain size evolution in natural populations.
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Affiliation(s)
- Zhongyi Yao
- Chengdu Institute of BiologyChinese Academy of SciencesChengduChina
- College of Life SciencesSichuan UniversityChengduChina
- University of Chinese Academy of SciencesBeijingChina
| | - Yin Qi
- Chengdu Institute of BiologyChinese Academy of SciencesChengduChina
| | - Bisong Yue
- College of Life SciencesSichuan UniversityChengduChina
| | - Jinzhong Fu
- Chengdu Institute of BiologyChinese Academy of SciencesChengduChina
- Department of Integrative BiologyUniversity of GuelphGuelphONCanada
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18
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Storks L, Powell BJ, Leal M. Peeking Inside the Lizard Brain: Neuron Numbers in Anolis and Its Implications for Cognitive Performance and Vertebrate Brain Evolution. Integr Comp Biol 2020; 63:icaa129. [PMID: 33175153 DOI: 10.1093/icb/icaa129] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Studies of vertebrate brain evolution have mainly focused on measures of brain size, particularly relative mass and its allometric scaling across lineages, commonly with the goal of identifying the substrates that underly differences in cognition. However, recent studies on birds and mammals have demonstrated that brain size is an imperfect proxy for neuronal parameters that underly function, such as the number of neurons that make up a given brain region. Here we present estimates of neuron numbers and density in two species of lizard, Anolis cristatellus and A. evermanni, representing the first such data from squamate species, and explore its implications for differences in cognitive performance and vertebrate brain evolution. The isotropic fractionator protocol outlined in this article is optimized for the unique challenges that arise when using this technique with lineages having nucleated erythrocytes and relatively small brains. The number and density of neurons and other cells we find in Anolis for the telencephalon, cerebellum, and the rest of the brain (ROB) follow similar patterns as published data from other vertebrate species. Anolis cristatellus and A. evermanni exhibited differences in their performance in a motor task frequently used to evaluate behavioral flexibility, which was not mirrored by differences in the number, density, or proportion of neurons in either the cerebellum, telencephalon, or ROB. However, the brain of A. evermanni had a significantly higher number of nonneurons and a higher nonneuron to neuron ratio across the whole brain, which could contribute to the observed differences in problem solving between A. cristatellus and A. evermanni. Although limited to two species, our findings suggest that neuron number and density in lizard brains scale similarly to endothermic vertebrates in contrast to the differences observed in brain to body mass relationships. Data from a wider range of species are necessary before we can fully understand vertebrate brain evolution at the neuronal level.
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Affiliation(s)
- Levi Storks
- Division of Biological Sciences, University of Missouri, Columbia, MO, USA
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Axelrod CJ, Laberge F, Robinson BW. Isolating the effects of ontogenetic niche shift on brain size development using pumpkinseed sunfish ecotypes. Evol Dev 2020; 22:312-322. [DOI: 10.1111/ede.12333] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- Caleb J. Axelrod
- Department of Integrative BiologyUniversity of Guelph Guelph Ontario Canada
| | - Frédéric Laberge
- Department of Integrative BiologyUniversity of Guelph Guelph Ontario Canada
| | - Beren W. Robinson
- Department of Integrative BiologyUniversity of Guelph Guelph Ontario Canada
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Yaxley KJ, Foley RA. Reconstructing the ancestral phenotypes of great apes and humans (Homininae) using subspecies-level phylogenies. Biol J Linn Soc Lond 2019. [DOI: 10.1093/biolinnean/blz140] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Abstract
Owing to their close affinity, the African great apes are of interest in the study of human evolution. Although numerous researchers have described the ancestors we share with these species with reference to extant great apes, few have done so with phylogenetic comparative methods. One obstacle to the application of these techniques is the within-species phenotypic variation found in this group. Here, we leverage this variation, modelling common ancestors using ancestral state reconstructions (ASRs) with reference to subspecies-level trait data. A subspecies-level phylogeny of the African great apes and humans was estimated from full-genome mitochondrial DNA sequences and used to implement ASRs for 14 continuous traits known to vary between great ape subspecies. Although the inclusion of within-species phenotypic variation increased the phylogenetic signal for our traits and improved the performance of our ASRs, whether this was done through the inclusion of subspecies phylogeny or through the use of existing methods made little difference. Our ASRs corroborate previous findings that the last common ancestor of humans, chimpanzees and bonobos was a chimp-like animal, but also suggest that the last common ancestor of humans, chimpanzees, bonobos and gorillas was an animal unlike any extant African great ape.
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Affiliation(s)
| | - Robert A Foley
- Leverhulme Centre for Human Evolutionary Studies, University of Cambridge, Cambridge, UK
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Griffing AH, Sanger TJ, Daza JD, Nielsen SV, Pinto BJ, Stanley EL, Gamble T. Embryonic development of a parthenogenetic vertebrate, the mourning gecko (
Lepidodactylus lugubris
). Dev Dyn 2019; 248:1070-1090. [DOI: 10.1002/dvdy.72] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Revised: 06/10/2019] [Accepted: 06/11/2019] [Indexed: 12/11/2022] Open
Affiliation(s)
- Aaron H. Griffing
- Department of Biological SciencesMarquette University Milwaukee Wisconsin
| | - Thomas J. Sanger
- Department of BiologyLoyola University in Chicago Chicago Illinois
| | - Juan D. Daza
- Department of Biological SciencesSam Houston State University Huntsville Texas
| | - Stuart V. Nielsen
- Department of HerpetologyFlorida Museum of Natural History Gainesville Florida
| | - Brendan J. Pinto
- Department of Biological SciencesMarquette University Milwaukee Wisconsin
| | - Edward L. Stanley
- Department of HerpetologyFlorida Museum of Natural History Gainesville Florida
| | - Tony Gamble
- Department of Biological SciencesMarquette University Milwaukee Wisconsin
- Milwaukee Public Museum Milwaukee Wisconsin
- Bell Museum of Natural HistoryUniversity of Minnesota Saint Paul Minnesota
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