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Brown KS, Caruso CM. The effect of experimental pollinator decline on pollinator-mediated selection on floral traits. Ecol Evol 2023; 13:e10706. [PMID: 37953983 PMCID: PMC10636310 DOI: 10.1002/ece3.10706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Accepted: 10/22/2023] [Indexed: 11/14/2023] Open
Abstract
Human-mediated environmental change, by reducing mean fitness, is hypothesized to strengthen selection on traits that mediate interactions among species. For example, human-mediated declines in pollinator populations are hypothesized to reduce mean seed production by increasing the magnitude of pollen limitation and thus strengthen pollinator-mediated selection on floral traits that increase pollinator attraction or pollen transfer efficiency. To test this hypothesis, we measured two female fitness components and six floral traits of Lobelia siphilitica plants exposed to supplemental hand-pollination, ambient open-pollination, or reduced open-pollination treatments. The reduced treatment simulated pollinator decline, while the supplemental treatment was used to estimate pollen limitation and pollinator-mediated selection. We found that plants in the reduced pollination treatment were significantly pollen limited, resulting in pollinator-mediated selection for taller inflorescences and more vibrant petals, both traits that could increase pollinator attraction. This contrasts with plants in the ambient pollination treatment, where reproduction was not pollen limited and there was not significant pollinator-mediated selection on any floral trait. Our results support the hypothesis that human-mediated environmental change can strengthen selection on traits of interacting species and suggest that these traits have the potential to evolve in response to changing environments.
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Affiliation(s)
- Kaitlyn S. Brown
- Department of Integrative BiologyUniversity of GuelphGuelphOntarioCanada
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2
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Hossack GC, Caruso CM. Simulated pollinator decline has similar effects on seed production of female and hermaphrodite Lobelia siphilitica, but different effects on selection on floral traits. Am J Bot 2023; 110:e16106. [PMID: 36401558 DOI: 10.1002/ajb2.16106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 11/06/2022] [Accepted: 11/10/2022] [Indexed: 06/16/2023]
Abstract
PREMISE Pollinator decline, by reducing seed production, is predicted to strengthen natural selection on floral traits. However, the effect of pollinator decline on gender dimorphic species (such as gynodioecious species, where plants produce female or hermaphrodite flowers) may differ between the sex morphs: if pollinator decline reduces the seed production of females more than hermaphrodites, then it should also have a larger effect on selection on floral traits in females than in hermaphrodites. METHODS To simulate pollinator decline, we experimentally reduced pollinator access to female and hermaphrodite Lobelia siphilitica plants. We compared the seed production of plants in the reduced pollination treatment to plants that were exposed to ambient pollination conditions. Within each treatment, we also measured directional selection on four floral traits of females and hermaphrodites. RESULTS Experimentally reducing pollination decreased seed production of both females and hermaphrodites by ~21%. Reducing pollination also strengthened selection on floral traits, but this effect was not larger in females than in hermaphrodites. Instead, reducing pollination intensified selection for taller inflorescences in hermaphrodites, but did not intensify selection on any floral trait in females. CONCLUSIONS Our results suggest that pollinator decline will not have a larger effect on either seed production or selection on floral traits of female plants. As such, any effect of pollinator decline on seed production may be similar for gender dimorphic and monomorphic species. However, the potential for floral traits of females (and thus of gender dimorphic species) to evolve in response to pollinator decline may be limited.
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Affiliation(s)
| | - Christina M Caruso
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, Canada
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3
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Lee KJ, Caruso CM. Plasticity in floral longevity and sex-phase duration of Lobelia siphilitica in response to simulated pollinator declines. Am J Bot 2022; 109:526-534. [PMID: 35253215 DOI: 10.1002/ajb2.1837] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Revised: 02/14/2022] [Accepted: 02/17/2022] [Indexed: 06/14/2023]
Abstract
PREMISE Pollinator declines can reduce the quantity and quality of pollination services, resulting in less pollen deposited on flowers and lower seed production by plants. In response to these reductions, plant species that cannot autonomously self-pollinate and thus are dependent on pollinators to set seed could plastically adjust their floral traits. Such plasticity could increase the opportunity for outcross pollination directly, as well as indirectly by affecting inflorescence traits. METHODS To test whether plants can respond to pollinator declines by plastically adjusting their floral traits, we simulated declines by experimentally reducing pollinator access to Lobelia siphilitica plants and measuring two traits of early- and late-season flowers: (1) floral longevity; and (2) sex-phase duration. To test whether plasticity in these floral traits affected inflorescence traits, we measured daily display size and phenotypic gender. RESULTS We found that experimentally reducing pollination did not affect female-phase duration, but did extend the male-phase duration of early-season flowers by 13% and the longevity of late-season flowers by 12.8%. However, plants with an extended male phase did not have a more male-biased phenotypic gender, and plants with an extended floral longevity did not have a larger daily display. CONCLUSIONS Our results suggest that plants can respond to pollinator declines by plastically adjusting both the longevity and sex-phase duration of their flowers. If this plasticity increases the opportunity for outcross pollination, then it could be one mechanism by which pollinator-dependent plant species maintain seed production as pollinators decline.
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Affiliation(s)
- Kiana J Lee
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
| | - Christina M Caruso
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
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Appiah-Madson HJ, Knox EB, Caruso CM, Case AL. Do Genetic Drift and Gene Flow Affect the Geographic Distribution of Female Plants in Gynodioecious Lobelia siphilitica? Plants (Basel) 2022; 11:825. [PMID: 35336707 PMCID: PMC8950786 DOI: 10.3390/plants11060825] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Revised: 03/18/2022] [Accepted: 03/18/2022] [Indexed: 06/14/2023]
Abstract
Variation in population sex ratio is particularly pronounced in gynodioecious angiosperms. Extremely high female frequencies in gynodioecious populations cannot be readily explained by selective forces alone. To assess the contributions of drift and gene flow to extreme sex-ratio variation, we documented sex ratio and population size in 92 populations of Lobelia siphilitica across its range and genotyped plants using plastid and nuclear genetic markers. Similarity in spatial patterns of genetic and demographic variables may suggest that drift and/or gene flow have contributed to population sex-ratio variation in L. siphilitica. We found strong spatial structuring of extremely high female frequencies: populations with >50% female plants are restricted to the south−central portion of the range. However, we did not detect any spatial structuring in population size nor metrics of genetic diversity, suggesting that extreme variation in female frequency is not strongly affected by drift or gene flow. Extreme sex-ratio variation is frequently observed in gynodioecious plants, but its causes are difficult to identify. Further investigation into mechanisms that create or maintain the spatial structure of sex ratios in gynodioecious species will provide much needed insight.
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Affiliation(s)
- Hannah J. Appiah-Madson
- Department of Marine and Environmental Science, Ocean Genome Legacy Center, Northeastern University, Nahant, MA 01908, USA
| | - Eric B. Knox
- Department of Biology, Indiana University, Bloomington, IN 47405, USA;
| | - Christina M. Caruso
- Department of Integrative Biology, University of Guelph, Guelph, ON N1G 2W1, Canada;
| | - Andrea L. Case
- Department of Biological Sciences, Kent State University, Kent, OH 44240, USA;
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Yakimowski SB, Teitel Z, Caruso CM. Defence by duplication: The relation between phenotypic glyphosate resistance and EPSPS gene copy number variation in Amaranthus palmeri. Mol Ecol 2021; 30:5328-5342. [PMID: 34662479 DOI: 10.1111/mec.16231] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Revised: 08/17/2021] [Accepted: 09/08/2021] [Indexed: 12/12/2022]
Abstract
Gene copy number variation (CNV) has been increasingly associated with organismal responses to environmental stress, but we know little about the quantitative relation between CNV and phenotypic variation. In this study we quantify the relation between variation in EPSPS (5-enolpyruvylshikimate-3-phosphate synthase) copy number using digital drop PCR and variation in phenotypic glyphosate resistance in 22 populations of Amaranthus palmeri (Palmer Amaranth), a range-expanding agricultural weed. Overall, we detected a significant positive relation between population mean copy number and resistance. The majority of populations exhibited high glyphosate resistance yet maintained low-resistance individuals, resulting in bimodality in many populations. We also investigated threshold models for the relation between copy number and resistance, and found evidence for a threshold of ~15 EPSPS copies: there was a steep increase in resistance below the threshold, followed by a much shallower increase. Across 924 individuals, as copy number increased the range of variation in resistance decreased, yielding an increasing frequency of high phenotypic resistance individuals. Among populations we detected a decline in variation (s.d.) as mean phenotypic resistance increased from moderate to high, consistent with the prediction that as phenotypic resistance increases in populations, stabilizing selection decreases variation in the trait. Our study demonstrates that populations of A. palmeri can harbour wide variation in EPSPS copy number and phenotypic glyphosate resistance, reflecting the history of, and template for future, resistance evolution.
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Affiliation(s)
| | - Zachary Teitel
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, Canada
| | - Christina M Caruso
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, Canada
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6
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Villellas J, Ehrlén J, Crone EE, Csergő AM, Garcia MB, Laine AL, Roach DA, Salguero-Gómez R, Wardle GM, Childs DZ, Elderd BD, Finn A, Munné-Bosch S, Bachelot B, Bódis J, Bucharova A, Caruso CM, Catford JA, Coghill M, Compagnoni A, Duncan RP, Dwyer JM, Ferguson A, Fraser LH, Griffoul E, Groenteman R, Hamre LN, Helm A, Kelly R, Laanisto L, Lonati M, Münzbergová Z, Nuche P, Olsen SL, Oprea A, Pärtel M, Petry WK, Ramula S, Rasmussen PU, Enri SR, Roeder A, Roscher C, Schultz C, Skarpaas O, Smith AL, Tack AJM, Töpper JP, Vesk PA, Vose GE, Wandrag E, Wingler A, Buckley YM. PHENOTYPIC PLASTICITY MASKS RANGE-WIDE GENETIC DIFFERENTIATION FOR VEGETATIVE BUT NOT REPRODUCTIVE TRAITS IN A SHORT-LIVED PLANT. Ecol Lett 2021; 24:2378-2393. [PMID: 34355467 DOI: 10.1111/ele.13858] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Revised: 05/13/2021] [Accepted: 05/19/2021] [Indexed: 12/12/2022]
Abstract
Genetic differentiation and phenotypic plasticity jointly shape intraspecific trait variation, but their roles differ among traits. In short-lived plants, reproductive traits may be more genetically determined due to their impact on fitness, whereas vegetative traits may show higher plasticity to buffer short-term perturbations. Combining a multi-treatment greenhouse experiment with observational field data throughout the range of a widespread short-lived herb, Plantago lanceolata, we (1) disentangled genetic and plastic responses of functional traits to a set of environmental drivers and (2) assessed how genetic differentiation and plasticity shape observational trait-environment relationships. Reproductive traits showed distinct genetic differentiation that largely determined observational patterns, but only when correcting traits for differences in biomass. Vegetative traits showed higher plasticity and opposite genetic and plastic responses, masking the genetic component underlying field-observed trait variation. Our study suggests that genetic differentiation may be inferred from observational data only for the traits most closely related to fitness.
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Affiliation(s)
- Jesus Villellas
- Departamento de Biodiversidad, Ecología y Evolución, Universidad Complutense de Madrid, Madrid, Spain.,School of Natural Sciences, Zoology, Trinity College Dublin, Dublin, Ireland
| | - Johan Ehrlén
- Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden
| | - Elizabeth E Crone
- Department of Biology, Tufts University, Medford, Massachusetts, USA
| | - Anna Mária Csergő
- School of Natural Sciences, Zoology, Trinity College Dublin, Dublin, Ireland.,Department of Botany and Soroksár Botanical Garden, Szent István University, Budapest, Hungary
| | - Maria B Garcia
- Department of Biodiversity Conservation and Ecosystem Restoration, Pyrenean Institute of Ecology (CSIC), Zaragoza, Spain
| | - Anna-Liisa Laine
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland.,Organismal & Evolutionary Biology Research Program, Faculty of Biological & Environmental Sciences, University of Helsinki, Helsinki, Finland
| | - Deborah A Roach
- Department of Biology, University of Virginia, Charlottesville, Virginia, USA
| | - Roberto Salguero-Gómez
- Department of Zoology, University of Oxford, Oxford, UK.,Max Planck Institute for Demographic Research, Rostock, Germany.,School of Biological Sciences, The University of Queensland, St Lucia, Queensland, Australia
| | - Glenda M Wardle
- School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales, Australia
| | - Dylan Z Childs
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield, UK
| | - Bret D Elderd
- Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana, USA
| | - Alain Finn
- School of Natural Sciences, Zoology, Trinity College Dublin, Dublin, Ireland
| | - Sergi Munné-Bosch
- Department of Evolutionary Biology, Ecology and Environmental Sciences, Faculty of Biology, University of Barcelona, Barcelona, Spain.,Institut de Recerca de la Biodiversitat, Universitat de Barcelona, Barcelona, Spain
| | - Benedicte Bachelot
- Department of Plant Biology, Ecology and Evolution, Oklahoma State University, Stillwater, Oklahoma, USA
| | - Judit Bódis
- Department of Plant Sciences and Biotechnology, Georgikon Faculty, University of Pannonia, Keszthely, Hungary
| | - Anna Bucharova
- Biodiversity and Ecosystem Research Group, Institut of Landscape Ecology, University of Münster, Germany.,Plant Evolutionary Ecology, Institut of Evolution and Ecology, University of Tübingen, Tübingen, Germany
| | - Christina M Caruso
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, Canada
| | - Jane A Catford
- Department of Geography, King's College London, London, UK.,Biological Sciences, University of Southampton, Southampton, UK
| | - Matthew Coghill
- Department of Natural Resource Sciences, Thompson Rivers University, Kamloops, British Columbia, Canada
| | - Aldo Compagnoni
- Institute of Biology, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Richard P Duncan
- Institute for Applied Ecology, University of Canberra, Canberra, Australian Capital Territory, Australia
| | - John M Dwyer
- School of Biological Sciences, The University of Queensland, St Lucia, Queensland, Australia.,CSIRO Land & Water, EcoSciences Precinct, Dutton Park, Queensland, Australia
| | | | - Lauchlan H Fraser
- Department of Natural Resource Sciences, Thompson Rivers University, Kamloops, British Columbia, Canada
| | | | | | - Liv Norunn Hamre
- Department of Environmental Sciences, Western Norway University of Applied Sciences, Sogndal, Norway
| | - Aveliina Helm
- Institute of Ecology and Earth Sciences, University of Tartu, Tartu, Estonia
| | - Ruth Kelly
- School of Natural Sciences, Zoology, Trinity College Dublin, Dublin, Ireland.,Agri-Food and Biosciences Institute, Belfast, Northern Ireland, UK
| | - Lauri Laanisto
- Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences, Tartu, Estonia
| | - Michele Lonati
- Department of Agriculture, Forest and Food Science, University of Torino, Grugliasco, Italy
| | - Zuzana Münzbergová
- Department of Botany, Faculty of Science, Charles University, Prague, Czech Republic.,Department of Population Ecology, Institute of Botany, Czech Academy of Sciences, Prague, Czech Republic
| | - Paloma Nuche
- School of Natural Sciences, Zoology, Trinity College Dublin, Dublin, Ireland
| | | | - Adrian Oprea
- Botanic Garden "Anastasie Fatu", University "Alexandru Ioan Cuza" Iaşi, Romania
| | - Meelis Pärtel
- Institute of Ecology and Earth Sciences, University of Tartu, Tartu, Estonia
| | - William K Petry
- Department of Plant & Microbial Biology, North Carolina State University, Raleigh, North Carolina, USA
| | - Satu Ramula
- Department of Biology, University of Turku, Turku, Finland
| | - Pil U Rasmussen
- Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden.,The National Research Centre for the Working Environment, Copenhagen, Denmark
| | - Simone Ravetto Enri
- Department of Agriculture, Forest and Food Science, University of Torino, Grugliasco, Italy
| | - Anna Roeder
- Department of Physiological Diversity, Helmholtz Centre for Environmental Research (UFZ), Leipzig, Germany.,German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Leipzig, Germany
| | - Christiane Roscher
- Department of Physiological Diversity, Helmholtz Centre for Environmental Research (UFZ), Leipzig, Germany.,German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Leipzig, Germany
| | - Cheryl Schultz
- School of Biological Sciences, Washington State University, Vancouver, Washington, USA
| | - Olav Skarpaas
- Natural History Museum, University of Oslo, Oslo, Norway
| | - Annabel L Smith
- School of Natural Sciences, Zoology, Trinity College Dublin, Dublin, Ireland.,School of Agriculture and Food Sciences, University of Queensland, Gatton, Queensland, Australia
| | - Ayco J M Tack
- Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden
| | | | - Peter A Vesk
- School of BioSciences, University of Melbourne, Melbourne, Victoria, Australia
| | - Gregory E Vose
- Department of Ecology and Evolutionary Biology, University of California, Irvine, California, USA
| | - Elizabeth Wandrag
- Institute for Applied Ecology, University of Canberra, Canberra, Australian Capital Territory, Australia.,Department of Biology, University of York, York, UK
| | - Astrid Wingler
- School of Biological, Earth & Environmental Sciences and Environmental Research Institute, University College Cork, Cork, Ireland
| | - Yvonne M Buckley
- School of Natural Sciences, Zoology, Trinity College Dublin, Dublin, Ireland.,School of Biological Sciences, The University of Queensland, St Lucia, Queensland, Australia
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Benoit AD, Caruso CM. A sit-and-wait predator, but not an active-pursuit predator, alters pollinator-mediated selection on floral traits. Ecology 2021; 102:e03506. [PMID: 34319595 DOI: 10.1002/ecy.3506] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/18/2020] [Revised: 05/12/2021] [Accepted: 05/25/2021] [Indexed: 12/27/2022]
Abstract
Indirect species interactions are ubiquitous in nature, often outnumbering direct species interactions. Yet despite evidence that indirect interactions have strong ecological effects, relatively little is known about whether they can shape adaptive evolution by altering the strength and/or direction of natural selection. We tested whether indirect interactions affect the strength and direction of pollinator-mediated selection on floral traits of the bumble-bee pollinated wildflower Lobelia siphilitica. We estimated the indirect effects of two pollinator predators with contrasting hunting modes: dragonflies (Aeshnidae and Corduliidae) and ambush bugs (Phymata americana, Reduviidae). Because dragonflies are active pursuit predators, we hypothesized that they would strengthen pollinator-mediated selection by weakening plant-pollinator interactions (i.e., a density-mediated indirect effect). In contrast, because ambush bugs are sit-and-wait predators, we hypothesized that they would weaken or reverse the direction of pollinator-mediated selection by altering pollinator foraging behavior (i.e., a trait-mediated indirect effect). Specifically, if ambush bugs hunt from plants with traits that attract pollinators (i.e., prey), then pollinators will spend less time visiting those plants, weakening or reversing the direction of selection on attractive floral traits. We did not find evidence that high dragonfly abundance strengthened selection on floral traits via a density-mediated indirect effect: neither pollen limitation (a proxy for the strength of plant-pollinator interactions) nor directional selection on floral traits of L. siphilitica differed significantly between high- and low-dragonfly abundance treatments. In contrast, we did find evidence that ambush bug presence affected selection on floral traits via a trait-mediated indirect effect: ambush bugs hunted from L. siphilitica plants with larger daily floral displays, reversing the direction of pollinator-mediated selection on daily display size. These results suggest that indirect species interactions have the potential to shape adaptive evolution by altering natural selection.
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Affiliation(s)
- Amanda D Benoit
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
| | - Christina M Caruso
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
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Giles GE, Hasselquist L, Caruso CM, Eddy MD. Load Carriage and Physical Exertion Influence Cognitive Control in Military Scenarios. Med Sci Sports Exerc 2020; 51:2540-2546. [PMID: 31274685 DOI: 10.1249/mss.0000000000002085] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
INTRODUCTION Physical exertion has both beneficial and detrimental effects on cognitive performance, particularly cognitive control. Research into physical exertion under conditions of load carriage is particularly important given that military personnel and first responders must perform optimally under such combinatorial physical stressors. The present work sought to characterize cognitive control as a function of physical exertion and load carriage in a military operational scenario. METHODS Thirty-one active-duty soldiers underwent a 4-h operationally relevant and fatiguing scenario that included two 1-h foot marches under load carriage conditions of 8.8, 47.2, 50.7 kg on each of three separate days. During each foot march, they completed five 5-min blocks of an auditory go/no-go task of response inhibition. RESULTS Results showed that response inhibition declined with increasing load carriage and physical exertion, as evidenced by lower proportion of correct responses, higher proportion of false alarms, and lower response sensitivity between all three load conditions, particularly upon successive foot marches and time blocks within each foot march. CONCLUSIONS The results support previous laboratory-based work on load carriage and physical exertion and suggest that deteriorations in cognitive control witnessed in laboratory settings are more pronounced within realistic operational scenarios akin to those encountered by military personnel and first responders.
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Affiliation(s)
- Grace E Giles
- US Army Combat Capabilities Development Command Soldier Center (CCDC Soldier Center), Natick, MA
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9
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Smith AL, Hodkinson TR, Villellas J, Catford JA, Csergő AM, Blomberg SP, Crone EE, Ehrlén J, Garcia MB, Laine AL, Roach DA, Salguero-Gómez R, Wardle GM, Childs DZ, Elderd BD, Finn A, Munné-Bosch S, Baudraz MEA, Bódis J, Brearley FQ, Bucharova A, Caruso CM, Duncan RP, Dwyer JM, Gooden B, Groenteman R, Hamre LN, Helm A, Kelly R, Laanisto L, Lonati M, Moore JL, Morales M, Olsen SL, Pärtel M, Petry WK, Ramula S, Rasmussen PU, Enri SR, Roeder A, Roscher C, Saastamoinen M, Tack AJM, Töpper JP, Vose GE, Wandrag EM, Wingler A, Buckley YM. Global gene flow releases invasive plants from environmental constraints on genetic diversity. Proc Natl Acad Sci U S A 2020; 117:4218-4227. [PMID: 32034102 PMCID: PMC7049112 DOI: 10.1073/pnas.1915848117] [Citation(s) in RCA: 59] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
When plants establish outside their native range, their ability to adapt to the new environment is influenced by both demography and dispersal. However, the relative importance of these two factors is poorly understood. To quantify the influence of demography and dispersal on patterns of genetic diversity underlying adaptation, we used data from a globally distributed demographic research network comprising 35 native and 18 nonnative populations of Plantago lanceolata Species-specific simulation experiments showed that dispersal would dilute demographic influences on genetic diversity at local scales. Populations in the native European range had strong spatial genetic structure associated with geographic distance and precipitation seasonality. In contrast, nonnative populations had weaker spatial genetic structure that was not associated with environmental gradients but with higher within-population genetic diversity. Our findings show that dispersal caused by repeated, long-distance, human-mediated introductions has allowed invasive plant populations to overcome environmental constraints on genetic diversity, even without strong demographic changes. The impact of invasive plants may, therefore, increase with repeated introductions, highlighting the need to constrain future introductions of species even if they already exist in an area.
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Affiliation(s)
- Annabel L Smith
- Zoology, School of Natural Sciences, Trinity College Dublin, Dublin 2, Ireland;
- School of Agriculture and Food Science, University of Queensland, Gatton, 4343, Australia
| | - Trevor R Hodkinson
- Botany, School of Natural Sciences, Trinity College Dublin, Dublin 2, Ireland
| | - Jesus Villellas
- Departamento Biogeografía y Cambio Global, Museo Nacional de Ciencias Naturales-Consejo Superior de Investigaciones Científicas (MNCN-CSIC), E-28006 Madrid, Spain
| | - Jane A Catford
- Department of Geography, King's College London, WC2B 4BG London, United Kingdom
| | - Anna Mária Csergő
- Zoology, School of Natural Sciences, Trinity College Dublin, Dublin 2, Ireland
- Department of Botany, Faculty of Horticultural Science, Szent István University, 1118 Budapest, Hungary
- Soroksár Botanical Garden, Faculty of Horticultural Science, Szent István University, 1118 Budapest, Hungary
| | - Simone P Blomberg
- School of Biological Sciences, University of Queensland, Brisbane, QLD 4072, Australia
| | | | - Johan Ehrlén
- Department of Ecology, Environment and Plant Sciences, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Maria B Garcia
- Pyrenean Institute of Ecology, CSIC, 50059 Zaragoza, Spain
| | - Anna-Liisa Laine
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, CH-8057 Zurich, Switzerland
- Research Centre for Ecological Change, Faculty of Biological and Environmental Sciences, University of Helsinki, FI-00014 Helsinki, Finland
| | - Deborah A Roach
- Department of Biology, University of Virginia, Charlottesville, VA 22904
| | | | - Glenda M Wardle
- School of Life and Environmental Sciences, The University of Sydney, Sydney, NSW 2006, Australia
| | - Dylan Z Childs
- Department of Animal and Plant Sciences, University of Sheffield, S10 2TN Sheffield, United Kingdom
| | - Bret D Elderd
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803
| | - Alain Finn
- Zoology, School of Natural Sciences, Trinity College Dublin, Dublin 2, Ireland
| | - Sergi Munné-Bosch
- Department of Evolutionary Biology, Ecology and Environmental Sciences, University of Barcelona, 08028 Barcelona, Spain
- Institut de Recerca de la Biodiversitat, University of Barcelona, 08028 Barcelona, Spain
| | - Maude E A Baudraz
- Zoology, School of Natural Sciences, Trinity College Dublin, Dublin 2, Ireland
| | - Judit Bódis
- Georgikon Faculty, University of Pannonia, H-8360 Keszthely, Hungary
| | - Francis Q Brearley
- Department of Natural Sciences, Manchester Metropolitan University, M1 5GD Manchester, United Kingdom
| | - Anna Bucharova
- Plant Evolutionary Ecology, Institute of Evolution and Ecology, University of Tübingen, 72074 Tübingen, Germany
- Ecosystem and Biodiversity Research Group, Institute of Landscape Ecology, University of Münster, 48149 Münster, Germany
| | - Christina M Caruso
- Department of Integrative Biology, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Richard P Duncan
- Institute for Applied Ecology, University of Canberra, Canberra, ACT 2617, Australia
| | - John M Dwyer
- School of Biological Sciences, University of Queensland, Brisbane, QLD 4072, Australia
- CSIRO Land & Water, Commonwealth Scientific and Industrial Research Organisation (CSIRO), Dutton Park, QLD 4102, Australia
| | - Ben Gooden
- CSIRO Health & Biosecurity, CSIRO, Black Mountain, ACT 2601, Australia
- School of Earth, Atmospheric and Life Sciences, Faculty of Science, Medicine and Health, University of Wollongong, Wollongong, NSW 2522, Australia
| | | | - Liv Norunn Hamre
- Department of Environmental Sciences, Western Norway University of Applied Sciences, N-6856 Sogndal, Norway
| | - Aveliina Helm
- Institute of Ecology and Earth Sciences, University of Tartu, 51005 Tartu, Estonia
| | - Ruth Kelly
- Zoology, School of Natural Sciences, Trinity College Dublin, Dublin 2, Ireland
| | - Lauri Laanisto
- Biodiversity and Nature Tourism, Estonian University of Life Sciences, 51006 Tartu, Estonia
| | - Michele Lonati
- Department of Agricultural, Forest and Food Science, University of Torino, 10015 Grugliasco, Italy
| | - Joslin L Moore
- School of Biological Sciences, Monash University, Clayton, VIC 3800, Australia
| | - Melanie Morales
- Department of Evolutionary Biology, Ecology and Environmental Sciences, University of Barcelona, 08028 Barcelona, Spain
- Research Group of Plant Biology under Mediterranean Conditions, Faculty of Biology, University of Balearic Islands, 07122 Palma de Mallorca, Spain
| | - Siri Lie Olsen
- Norwegian Institute for Nature Research, N-0349 Oslo, Norway
| | - Meelis Pärtel
- Institute of Ecology and Earth Sciences, University of Tartu, 51005 Tartu, Estonia
| | - William K Petry
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544
| | - Satu Ramula
- Department of Biology, University of Turku, 20014 Turku, Finland
| | - Pil U Rasmussen
- Department of Ecology, Environment and Plant Sciences, Stockholm University, SE-106 91 Stockholm, Sweden
- The National Research Centre for the Working Environment, 2100 København Ø, Denmark
| | - Simone Ravetto Enri
- Department of Agricultural, Forest and Food Science, University of Torino, 10015 Grugliasco, Italy
| | - Anna Roeder
- Department of Physiological Diversity, Helmholtz Centre for Environmental Research - UFZ, 04103 Leipzig, Germany
- German Centre for Integrative Biodiversity Research Halle-Jena-Leipzig (iDiv), 04318 Leipzig, Germany
| | - Christiane Roscher
- Department of Physiological Diversity, Helmholtz Centre for Environmental Research - UFZ, 04103 Leipzig, Germany
- German Centre for Integrative Biodiversity Research Halle-Jena-Leipzig (iDiv), 04318 Leipzig, Germany
| | - Marjo Saastamoinen
- Helsinki Institute of Life Science, University of Helsinki, 00100 Helsinki, Finland
- Organismal and Evolutionary Research Programme, University of Helsinki, 00014 Helsinki, Finland
| | - Ayco J M Tack
- Department of Ecology, Environment and Plant Sciences, Stockholm University, SE-106 91 Stockholm, Sweden
| | | | - Gregory E Vose
- Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697
| | - Elizabeth M Wandrag
- Institute for Applied Ecology, University of Canberra, Canberra, ACT 2617, Australia
- School of Environmental and Rural Science, University of New England, Armidale, NSW 2351, Australia
| | - Astrid Wingler
- School of Biological, Earth & Environmental Sciences and Environmental Research Institute, University College Cork, Cork T23 N73K, Ireland
| | - Yvonne M Buckley
- Zoology, School of Natural Sciences, Trinity College Dublin, Dublin 2, Ireland
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10
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Panique H, Caruso CM. Simulated pollinator declines intensify selection on floral traits that facilitate selfing and outcrossing in Impatiens capensis. Am J Bot 2020; 107:148-154. [PMID: 31828763 DOI: 10.1002/ajb2.1403] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Accepted: 11/07/2019] [Indexed: 06/10/2023]
Abstract
PREMISE Anthropogenic environmental change is causing pollinator populations to decline. These declines should intensify selection for floral traits that facilitate outcrossing by making plants more attractive to pollinators and/or for floral traits that facilitate selfing in the absence of pollinators. However, the effect of pollinator declines on selection on floral traits could be modified by other environmental factors such as herbivores. METHODS We studied the effect of simulated pollinator declines on selection on floral traits of Impatiens capensis, a mixed-mating species that produces both obligately selfing cleistogamous flowers and primarily outcrossing chasmogamous flowers. We measured directional selection differentials via seeds per plant on two traits that facilitate outcrossing (chasmogamous flower size and number) and one trait that facilitates selfing (cleistogamous flower number) in ambient, reduced pollinator access, and reduced pollinator access combined with increased foliar herbivory treatments. RESULTS Reduced pollinator access intensified selection for larger chasmogamous flowers and more cleistogamous flowers. In contrast, increased herbivory did not affect selection on any floral trait. CONCLUSIONS Reduced pollinator access intensified selection for a trait that facilitates outcrossing, suggesting that even species such as I. capensis that can autonomously self-pollinate have the potential to respond to pollinator declines by evolving floral traits that reinforce interactions between plants and pollinators. However, reduced pollinator access also intensified selection for a trait that facilitates selfing, suggesting that I. capensis could adapt to pollinator declines by evolving floral traits that maintain the production of both selfed and outcrossed seeds.
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Affiliation(s)
- Hazel Panique
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, Canada
| | - Christina M Caruso
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, Canada
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11
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Adhikari B, Caruso CM, Case AL. Beyond balancing selection: frequent mitochondrial recombination contributes to high-female frequencies in gynodioecious Lobelia siphilitica (Campanulaceae). New Phytol 2019; 224:1381-1393. [PMID: 31442304 DOI: 10.1111/nph.16136] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2019] [Accepted: 08/13/2019] [Indexed: 06/10/2023]
Abstract
Gynodioecy is a sexual system in which females and hermaphrodites co-occur. In most gynodioecious angiosperms, sex is determined by an interaction between mitochondrial male-sterility genes (CMS) that arise via recombination and nuclear restorer alleles that evolve to suppress them. In theory, gynodioecy occurs when multiple CMS types are maintained at equilibrium frequencies by balancing selection. However, some gynodioecious populations contain very high frequencies of females. High female frequencies are not expected under balancing selection, but could be explained by the repeated introduction of novel CMS types. To test for balancing selection and/or the repeated introduction of novel CMS, we characterised cytoplasmic haplotypes from 61 populations of Lobelia siphilitica that vary widely in female frequency. We confirmed that mitotype diversity and female frequency were positively correlated across populations, consistent with balancing selection. However, while low-female populations hosted mostly common mitotypes, high-female populations and female plants hosted mostly rare, recombinant mitotypes likely to carry novel CMS types. Our results suggest that balancing selection maintains established CMS types across this species, but extreme female frequencies result from frequent invasion by novel CMS types. We conclude that balancing selection alone cannot account for extreme population sex-ratio variation within a gynodioecious species.
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Affiliation(s)
- Binaya Adhikari
- Department of Biological Sciences, Kent State University, Kent, OH, 44240, USA
- Department of Biological and Environmental Sciences, Longwood University, Farmville, VA, 23909, USA
| | - Christina M Caruso
- Department of Integrative Biology, University of Guelph, Guelph, ON, N1G 2W1, Canada
| | - Andrea L Case
- Department of Biological Sciences, Kent State University, Kent, OH, 44240, USA
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12
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Caruso CM, Eisen KE, Martin RA, Sletvold N. A meta-analysis of the agents of selection on floral traits. Evolution 2018; 73:4-14. [PMID: 30411337 DOI: 10.1111/evo.13639] [Citation(s) in RCA: 86] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2018] [Revised: 10/23/2018] [Accepted: 10/24/2018] [Indexed: 01/03/2023]
Abstract
Floral traits are hypothesized to evolve primarily in response to selection by pollinators. However, selection can also be mediated by other environmental factors. To understand the relative importance of pollinator-mediated selection and its variation among trait and pollinator types, we analyzed directional selection gradients on floral traits from experiments that manipulated the environment to identify agents of selection. Pollinator-mediated selection was stronger than selection by other biotic factors (e.g., herbivores), but similar in strength to selection by abiotic factors (e.g., soil water), providing partial support for the hypothesis that floral traits evolve primarily in response to pollinators. Pollinator-mediated selection was stronger on pollination efficiency traits than on other trait types, as expected if efficiency traits affect fitness via interactions with pollinators, but other trait types also affect fitness via other environmental factors. In addition to varying among trait types, pollinator-mediated selection varied among pollinator taxa: selection was stronger when bees, long-tongued flies, or birds were the primary visitors than when the primary visitors were Lepidoptera or multiple animal taxa. Finally, reducing pollinator access to flowers had a relatively small effect on selection on floral traits, suggesting that anthropogenic declines in pollinator populations would initially have modest effects on floral evolution.
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Affiliation(s)
- Christina M Caruso
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
| | - Katherine E Eisen
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada.,Current Address: Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, New York, 14853
| | - Ryan A Martin
- Department of Biology, Case Western Reserve University, Cleveland, Ohio, 44106
| | - Nina Sletvold
- Department of Ecology and Genetics, Uppsala University, Uppsala, 751 05, Sweden
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13
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Siepielski AM, Morrissey MB, Buoro M, Carlson SM, Caruso CM, Clegg SM, Coulson T, DiBattista J, Gotanda KM, Francis CD, Hereford J, Kingsolver JG, Augustine KE, Kruuk LEB, Martin RA, Sheldon BC, Sletvold N, Svensson EI, Wade MJ, MacColl ADC. Response to Comment on “Precipitation drives global variation in natural selection”. Science 2018; 359:359/6374/eaan5760. [DOI: 10.1126/science.aan5760] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Accepted: 08/28/2017] [Indexed: 11/02/2022]
Affiliation(s)
- Adam M. Siepielski
- Department of Biological Sciences, University of Arkansas, Fayetteville, AR, USA
| | | | - Mathieu Buoro
- Department of Environmental Science, Policy and Management, University of California, Berkeley, CA, USA
| | - Stephanie M. Carlson
- Department of Environmental Science, Policy and Management, University of California, Berkeley, CA, USA
| | - Christina M. Caruso
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, Canada
| | - Sonya M. Clegg
- Edward Grey Institute, Department of Zoology, University of Oxford, Oxford, UK
| | - Tim Coulson
- Department of Zoology, University of Cambridge, Cambridge, UK
| | - Joseph DiBattista
- Department of Environment and Agriculture, Curtin University, Perth, WA, Australia
| | - Kiyoko M. Gotanda
- Department of Zoology, University of Cambridge, Cambridge, UK
- Redpath Museum and Department of Biology, McGill University, Montreal, Quebec, Canada
| | - Clinton D. Francis
- Department of Biological Sciences, California Polytechnic State University, San Luis Obispo, CA, USA
| | - Joe Hereford
- Department of Evolution and Ecology, University of California, Davis, CA, USA
| | - Joel G. Kingsolver
- Department of Biology, University of North Carolina, Chapel Hill, NC, USA
| | - Kate E. Augustine
- Department of Biology, University of North Carolina, Chapel Hill, NC, USA
| | - Loeske E. B. Kruuk
- Research School of Biology, Australian National University, Canberra, ACT, Australia
| | - Ryan A. Martin
- Department of Biology, Case Western Reserve University, Cleveland, OH, USA
| | - Ben C. Sheldon
- Edward Grey Institute, Department of Zoology, University of Oxford, Oxford, UK
| | - Nina Sletvold
- Department of Ecology and Genetics, Uppsala University, Norbyvägen, Uppsala, Sweden
| | | | - Michael J. Wade
- Department of Biology, Indiana University, Bloomington, IN, USA
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14
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Siepielski AM, Morrissey MB, Buoro M, Carlson SM, Caruso CM, Clegg SM, Coulson T, DiBattista J, Gotanda KM, Francis CD, Hereford J, Kingsolver JG, Augustine KE, Kruuk LEB, Martin RA, Sheldon BC, Sletvold N, Svensson EI, Wade MJ, MacColl ADC. Precipitation drives global variation in natural selection. Science 2017; 355:959-962. [PMID: 28254943 DOI: 10.1126/science.aag2773] [Citation(s) in RCA: 183] [Impact Index Per Article: 26.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Revised: 06/27/2016] [Accepted: 02/02/2017] [Indexed: 12/31/2022]
Abstract
Climate change has the potential to affect the ecology and evolution of every species on Earth. Although the ecological consequences of climate change are increasingly well documented, the effects of climate on the key evolutionary process driving adaptation-natural selection-are largely unknown. We report that aspects of precipitation and potential evapotranspiration, along with the North Atlantic Oscillation, predicted variation in selection across plant and animal populations throughout many terrestrial biomes, whereas temperature explained little variation. By showing that selection was influenced by climate variation, our results indicate that climate change may cause widespread alterations in selection regimes, potentially shifting evolutionary trajectories at a global scale.
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Affiliation(s)
- Adam M Siepielski
- Department of Biological Sciences, University of Arkansas, Fayetteville, AR, USA.
| | | | - Mathieu Buoro
- Department of Environmental Science, Policy and Management, University of California-Berkeley, Berkeley, CA, USA
| | - Stephanie M Carlson
- Department of Environmental Science, Policy and Management, University of California-Berkeley, Berkeley, CA, USA
| | - Christina M Caruso
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, Canada
| | - Sonya M Clegg
- Edward Grey Institute, Department of Zoology, University of Oxford, Oxford, UK.,Environmental Futures Research Institute, Griffith University, 170 Kessels Road, Nathan, QLD, Australia
| | - Tim Coulson
- Department of Zoology, University of Oxford, Oxford, UK
| | - Joseph DiBattista
- Department of Environment and Agriculture, Curtin University, Perth, WA, Australia
| | - Kiyoko M Gotanda
- Department of Zoology, University of Oxford, Oxford, UK.,Redpath Museum and Department of Biology, McGill University, Montreal, Quebec, Canada
| | - Clinton D Francis
- Department of Biological Sciences, California Polytechnic State University, San Luis Obispo, CA, USA
| | - Joe Hereford
- Department of Evolution and Ecology, University of California, Davis, CA, USA
| | - Joel G Kingsolver
- Department of Biology, University of North Carolina, Chapel Hill, NC, USA
| | - Kate E Augustine
- Department of Biology, University of North Carolina, Chapel Hill, NC, USA
| | - Loeske E B Kruuk
- Research School of Biology, The Australian National University, Canberra, ACT, Australia
| | - Ryan A Martin
- Department of Biology, Case Western Reserve University, Cleveland, OH, USA
| | - Ben C Sheldon
- Edward Grey Institute, Department of Zoology, University of Oxford, Oxford, UK
| | - Nina Sletvold
- Department of Ecology and Genetics, Uppsala University, Norbyvägen, Uppsala, Sweden
| | | | - Michael J Wade
- Department of Biology, Indiana University, Bloomington, Indiana, USA
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15
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Caruso CM, Martin RA, Sletvold N, Morrissey MB, Wade MJ, Augustine KE, Carlson SM, MacColl ADC, Siepielski AM, Kingsolver JG. What Are the Environmental Determinants of Phenotypic Selection? A Meta-analysis of Experimental Studies. Am Nat 2017; 190:363-376. [DOI: 10.1086/692760] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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16
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Bailey MF, Case AL, Caruso CM. Physiological effects of temperature do not explain prevalence of females in populations of gynodioecious Lobelia siphilitica growing in warmer climates. Am J Bot 2017; 104:411-418. [PMID: 28325832 DOI: 10.3732/ajb.1600380] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Accepted: 02/22/2017] [Indexed: 06/06/2023]
Abstract
PREMISE OF THE STUDY Gynodioecy is a sexual polymorphism whereby female and hermaphroditic plants co-occur within populations. In many gynodioecious species, stressful abiotic environments are associated with higher frequencies of females. This association suggests that abiotic stress affects the relative fitness of females and hermaphrodites and, thus, the maintenance of gynodioecy. METHODS To test whether abiotic stress affects the fitness of females and hermaphrodites, we grew open-pollinated Lobelia siphilitica families in temperature regimes characteristic of the southern portion of the species' range (where females are common) and the northern portion of the range (where females are rare). We measured physiological and phenological traits that are indicative of heat stress, and fitness components of females and hermaphrodites that could affect the maintenance of gynodioecy. KEY RESULTS Contrary to expectations if growth at high temperatures is stressful, we found that the hot treatment increased leaf chlorophyll content, decreased the percentage of plants that delayed flowering initiation, and did not affect the quantum efficiency of photosystem II. Growth at high temperatures did not affect the magnitude of the difference in rosette size (a correlate of flower number) between females and hermaphrodites, or the variance in pollen viability among hermaphrodites. CONCLUSIONS We found that growing-season temperatures typical of high female L. siphilitica populations were not stressful and did not affect either the fitness of females compared to hermaphrodites or variation in fitness among hermaphrodites. Consequently, further research is necessary to explain correlations between abiotic environmental factors and the frequency of females in this and other gynodioecious species.
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Affiliation(s)
- Maia F Bailey
- Department of Biology, Providence College, Providence, Rhode Island 02918, USA
| | - Andrea L Case
- Department of Biological Sciences, Kent State University, Kent, Ohio 44242, USA
| | - Christina M Caruso
- Department of Integrative Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
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17
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Rivkin LR, Case AL, Caruso CM. Why is gynodioecy a rare but widely distributed sexual system? Lessons from the Lamiaceae. New Phytol 2016; 211:688-696. [PMID: 26991013 DOI: 10.1111/nph.13926] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Accepted: 02/06/2016] [Indexed: 06/05/2023]
Abstract
Gynodioecy, a sexual system where females and hermaphrodites co-occur, is found in << 1% of angiosperm species. To understand why gynodioecy is rare, we need to understand why females are maintained in some lineages, but not in others. We modelled the evolution of gynodioecy in the Lamiaceae, and investigated whether transition rates between gynodioecious and nongynodioecious states varied across the family. We also investigated whether the evolution of gynodioecy was correlated with the evolution of a herbaceous growth form and temperate distribution. Transition rates differed between Lamiaceae subfamilies. In the Nepetoideae, there were many transitions towards gynodioecy (n = 11), but also many reversions to nongynodioecy (n = 29). In addition, a herbaceous growth form, but not a temperate distribution, affected the rate of transitions both towards and away from gynodioecy; transitions towards gynodioecy occurred ˜16 times more frequently and transitions away from gynodioecy occurred ˜11 times more frequently in herbaceous lineages than in woody lineages. Within the Lamiaceae, lineages in which gynodioecy has frequently evolved also have a high rate of reversions to the nongynodioecious state. Consequently, to understand why gynodioecy is rare, we need to understand why sexual systems are more evolutionarily labile in some lineages than in others.
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Affiliation(s)
- L Ruth Rivkin
- Department of Integrative Biology, University of Guelph, Guelph, ON, N1G 2W1, Canada
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, M5S 3B2, Canada
| | - Andrea L Case
- Department of Biological Sciences, Kent State University, Kent, OH, 44242-0001, USA
| | - Christina M Caruso
- Department of Integrative Biology, University of Guelph, Guelph, ON, N1G 2W1, Canada
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18
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Caruso CM, Parachnowitsch AL. Do Plants Eavesdrop on Floral Scent Signals? Trends Plant Sci 2016; 21:9-15. [PMID: 26476624 DOI: 10.1016/j.tplants.2015.09.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Revised: 09/02/2015] [Accepted: 09/07/2015] [Indexed: 05/18/2023]
Abstract
Plants emit a diverse array of volatile organic compounds that can function as cues to other plants. Plants can use volatiles emitted by neighbors to gain information about their environment, and respond by adjusting their phenotype. Less is known about whether the many different volatile signals that plants emit are all equally likely to function as cues to other plants. We review evidence for the function of floral volatile signals and conclude that plants are as likely to perceive and respond to floral volatiles as to other, better-studied volatiles. We propose that eavesdropping on floral volatile cues is particularly likely to be adaptive because plants can respond to these cues by adjusting traits that directly affect pollination and mating.
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Affiliation(s)
- Christina M Caruso
- Department of Integrative Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
| | - Amy L Parachnowitsch
- Plant Ecology and Evolution, Evolutionary Biology Centre, Uppsala University, 75236 Uppsala, Sweden
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19
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Rivkin LR, Case AL, Caruso CM. Frequency-dependent fitness in gynodioecious Lobelia siphilitica. Evolution 2015; 69:1232-43. [PMID: 25824809 DOI: 10.1111/evo.12654] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2014] [Accepted: 03/19/2015] [Indexed: 12/30/2022]
Abstract
Selection is frequency dependent when an individual's fitness depends on the frequency of its phenotype. Frequency-dependent selection should be common in gynodioecious plants, where individuals are female or hermaphroditic; if the fitness of females is limited by the availability of pollen to fertilize their ovules, then they should have higher fitness when rare than when common. To test whether the fitness of females is frequency dependent, we manipulated the sex ratio in arrays of gynodioecious Lobelia siphilitica. To test whether fitness was frequency dependent because of variation in pollen availability, we compared open-pollinated and supplemental hand-pollinated plants. Open-pollinated females produced more seeds when they were rare than when they were common, as expected if fitness is negatively frequency dependent. However, hand-pollinated females also produced more seeds when they were rare, indicating that variation in pollen availability was not the cause of frequency-dependent fitness. Instead, fitness was frequency dependent because both hand- and open-pollinated females opened more flowers when they were rare than when they were common. This plasticity in the rate of anthesis could cause fitness to be frequency dependent even when reproduction is not pollen limited, and thus expand the conditions under which frequency-dependent selection operates in gynodioecious species.
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Affiliation(s)
- L Ruth Rivkin
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada.
| | - Andrea L Case
- Department of Biological Sciences, Kent State University, Kent, Ohio, 44242
| | - Christina M Caruso
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
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20
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Lieberman HR, Thompson LA, Caruso CM, Niro PJ, Mahoney CR, McClung JP, Caron GR. The catecholamine neurotransmitter precursor tyrosine increases anger during exposure to severe psychological stress. Psychopharmacology (Berl) 2015; 232:943-51. [PMID: 25220844 PMCID: PMC4325185 DOI: 10.1007/s00213-014-3727-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/20/2013] [Accepted: 08/22/2014] [Indexed: 12/01/2022]
Abstract
RATIONALE Acute stress produces behavioral and physiological changes modulated by central catecholamines (CA). Stress increases CA activity, and depletion of CA stores reduces responses to stress. Increasing CA activity by administration of the dietary amino acid CA precursor tyrosine may increase responsiveness to stress. This study determined whether tyrosine enhances the ability of humans to respond to severe stress. METHODS Severe psychological stress was generated during training at Survival, Evasion, Resistance, and Escape (SERE) School. The acute stressor consisted of two mock interrogations conducted during several days of simulated captivity. Seventy-eight healthy male and female military personnel participated in this double-blind, between-subjects study, in which they received either tyrosine (300 mg/kg, N = 36) or placebo (N = 36). Tyrosine (or placebo) was administered in food bars in two doses of 150 mg/kg each approximately 60 min before each mock interrogation. Mood (Profile of Mood States), saliva cortisol, and heart rate (HR) were assessed prior to stress exposure during a week of academic training preceding mock captivity and immediately following the mock interrogations. RESULTS The severe stress produced robust effects on mood (i.e., increased tension, depression, anger, fatigue, vigor, and confusion; p < .001), cortisol, and HR (p < .001). Tyrosine increased anger (p = .002, ANOVA treatment condition by test session interaction) during stress but had no other effects. CONCLUSION Tyrosine did not alter most subjective or physiological responses to severe acute stress, but it increased ratings of anger. The modest increase in anger may be an adaptive emotional response in stressful environments.
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Affiliation(s)
- Harris R. Lieberman
- Military Nutrition Division, US Army Research Institute of Environmental Medicine, Kansas Street, Natick, MA 01760 USA
| | - Lauren A. Thompson
- Military Nutrition Division, US Army Research Institute of Environmental Medicine, Kansas Street, Natick, MA 01760 USA
| | - Christina M. Caruso
- Military Nutrition Division, US Army Research Institute of Environmental Medicine, Kansas Street, Natick, MA 01760 USA
| | - Philip J. Niro
- Military Nutrition Division, US Army Research Institute of Environmental Medicine, Kansas Street, Natick, MA 01760 USA
| | - Caroline R. Mahoney
- Cognitive Sciences, US Army Natick Soldier Research, Development, and Engineering Center, Kansas Street, Natick, MA 01760 USA
| | - James P. McClung
- Military Nutrition Division, US Army Research Institute of Environmental Medicine, Kansas Street, Natick, MA 01760 USA
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21
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Caruso CM, Case AL, Bailey MF. The evolutionary ecology of cytonuclear interactions in angiosperms. Trends Plant Sci 2012; 17:638-643. [PMID: 22784826 DOI: 10.1016/j.tplants.2012.06.006] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2012] [Revised: 06/08/2012] [Accepted: 06/13/2012] [Indexed: 06/01/2023]
Abstract
Interactions between cytoplasmic and nuclear genomes have significant evolutionary consequences. In angiosperms, the most common cytonuclear interaction is between mitochondrial genes that disrupt pollen production (cytoplasmic male sterility, CMS) and nuclear genes that restore it (nuclear male fertility restorers, Rf). The outcome of CMS/Rf interactions can depend on whether Rf alleles have negative pleiotropic effects on fitness. Although these fitness costs are often considered to be independent of the ecological context, we argue that the effects of Rf alleles on fitness should be context dependent. Thus, measuring the cost of restoration across a range of environments could help explain geographic and phylogenetic variation in the distribution of Rf alleles and the outcome of CMS/Rf interactions.
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Affiliation(s)
- Christina M Caruso
- Department of Integrative Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
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Caruso CM, Case AL. TESTING MODELS OF SEX RATIO EVOLUTION IN A GYNODIOECIOUS PLANT: FEMALE FREQUENCY COVARIES WITH THE COST OF MALE FERTILITY RESTORATION. Evolution 2012; 67:561-6. [DOI: 10.1111/j.1558-5646.2012.01798.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Parachnowitsch AL, Caruso CM, Campbell SA, Kessler A. Lobelia siphilitica plants that escape herbivory in time also have reduced latex production. PLoS One 2012; 7:e37745. [PMID: 22662205 PMCID: PMC3360611 DOI: 10.1371/journal.pone.0037745] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2011] [Accepted: 04/26/2012] [Indexed: 12/20/2022] Open
Abstract
Flowering phenology is an important determinant of a plant’s reproductive success. Both assortative mating and niche construction can result in the evolution of correlations between phenology and other reproductive, functional, and life history traits. Correlations between phenology and herbivore defence traits are particularly likely because the timing of flowering can allow a plant to escape herbivory. To test whether herbivore escape and defence are correlated, we estimated phenotypic and genetic correlations between flowering phenology and latex production in greenhouse-grown Lobelia siphilitica L. (Lobeliaceae). Lobelia siphilitica plants that flower later escape herbivory by a specialist pre-dispersal seed predator, and thus should invest fewer resources in defence. Consistent with this prediction, we found that later flowering was phenotypically and genetically correlated with reduced latex production. To test whether herbivore escape and latex production were costly, we also measured four fitness correlates. Flowering phenology was negatively genetically correlated with three out of four fitness estimates, suggesting that herbivore escape can be costly. In contrast, we did not find evidence for costs of latex production. Generally, our results suggest that herbivore escape and defence traits will not evolve independently in L. siphilitica.
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Affiliation(s)
- Amy L Parachnowitsch
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, New York, United States of America.
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Pasiakos SM, Caruso CM, Kellogg MD, Kramer FM, Lieberman HR. Appetite and endocrine regulators of energy balance after 2 days of energy restriction: insulin, leptin, ghrelin, and DHEA-S. Obesity (Silver Spring) 2011; 19:1124-30. [PMID: 21212768 DOI: 10.1038/oby.2010.316] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Using a double-blind, placebo-controlled crossover design, the effects of 48 h near complete energy restriction on endocrine regulators of appetite and satiety were assessed. Twelve men and one woman participated in this controlled, 2-day diet intervention study. One experimental trial was completed in a calorie deprived state (CAL-DEP; <10% of estimated energy requirements) and others in a fed condition (carbohydrate only and carbohydrate and fat; data were pooled and compared to CAL-DEP). Test meals containing prescribed energy intake and indistinguishable in sensory characteristics were provided during each trial. Glucose, insulin, leptin, ghrelin, cortisol, dehydroepiandrosterone-sulfate (DHEA-S), and satiety were repeatedly assessed. Mean glucose, insulin, and leptin concentrations were lower (P < 0.0001) for CAL-DEP compared to the fully fed (FED) state. Ghrelin and DHEA-S were higher (P < 0.0001) for CAL-DEP relative to FED. Cortisol levels declined each day regardless of diet (P < 0.0001) but were 32% higher (P < 0.01) at the conclusion of the session for CAL-DEP compared to FED. Satiety was 25% lower (P < 0.0001) for CAL-DEP relative to FED and decreased (P < 0.0001) over time regardless of diet. In the FED state, insulin (r = 0.55), glucose (r = 0.76), cortisol (r = -0.59), and DHEA-S (r = -0.62) were associated (P < 0.05) with satiety, but not during CAL-DEP. These findings show that 2 days of severe energy restriction alter several endocrine regulators of appetite independent of perception of increased hunger suggesting a physiological mechanism to explain overeating following acute periods of severe energy restriction.
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Affiliation(s)
- Stefan M Pasiakos
- Military Nutrition Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts, USA.
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Abstract
*In many gynodioecious plants, sex is determined by cytoplasmic male sterility genes (CMS) and nuclear male fertility restorers (Rf). Models predict that the costs of restoration are important determinants of population sex ratios. However, current approaches to the estimation of these costs require prior identification of CMS genotypes, information that is available for few species. *We tested a novel approach to estimating the cost of restoration in natural populations without determining CMS or Rf genotypes. We used estimates of pollen viability and offspring sex ratios from open- and hand-pollinated families of Lobelia siphilitica to test whether the cost of restoration, expressed as low pollen viability, is higher in populations with more females. *Among populations with CMS, we found that variation in pollen viability was higher in small populations with more females, as expected if the proportion of females within populations increases with the maximum cost of restoration. In controlled crosses, families with low pollen viability also produced fewer females, suggesting that variation in viability is primarily determined by the number and frequency of Rf alleles carried. *This approach to estimating the cost of restoration can be applied to other cytonuclear gynodioecious species, offering new opportunities for testing gynodioecy models in the wild.
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Affiliation(s)
- Andrea L Case
- Department of Biological Sciences, Kent State University, Kent, OH, USA.
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Abstract
Physiological changes with ontogeny are common in plants. Although ontogenetic changes are hypothesized to improve plant function, their adaptive significance has rarely been tested. Here, we estimated phenotypic selection on ontogenetic change in photosynthesis (A) and stomatal conductance (g(s)) of Avena barbata. We tested whether ontogenetic changes in A and g(s) increased fitness in wet and dry soil environments. To determine whether evolution in response to this selection would be constrained, we estimated the heritability of ontogenetic change in physiology, as well as cross-environment genetic correlations. Ontogenetic change in A, but not g(s), was adaptive in the wet soil environment; plants that maintained or increased A from the prereproductive to the reproductive phase had higher fitness. In the dry soil environment, ontogenetic change in A and g(s) was adaptively neutral. We detected significant genetic variation for ontogenetic change in A and g(s), but no cross-environment genetic correlations, suggesting that the evolution of these traits would not be genetically constrained. We demonstrate that ontogenetic changes in physiological traits can increase fitness but the adaptive value of these changes varies among traits and environments.
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Affiliation(s)
| | | | - Mark E Sherrard
- Department of Integrative Biology, University of Guelph, Guelph, Ontario N1G 2W1 Canada
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Abstract
Herbivores that oviposit in flowers of animal-pollinated plants depend on pollinators for seed production and are therefore expected to choose flowers that attract pollinators. This provides a mechanism by which seed herbivores and pollinators could impose conflicting selection on floral traits. We measured phenotypic selection on floral traits of Lobelia siphilitica (Lobeliaceae) via female fitness to determine the relative strength of selection by pollinators and a specialist predispersal seed herbivore. We were able to attribute selection on flowering phenology to the herbivores. However, no selection could be attributed to pollinators, resulting in no conflicting selection on floral traits. Unlike pollinators, whose preference for certain floral traits does not always translate into higher fitness, any discrimination by seed herbivores is likely to decrease fitness of the preferred floral phenotype. Thus predispersal seed herbivores may be a significant agent of selection on floral traits.
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Affiliation(s)
- Amy L Parachnowitsch
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
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Abstract
Sexual dimorphism is common in plants and animals. Although this dimorphism is often assumed to be adaptive, natural selection has rarely been measured on sexually dimorphic traits of plants. We measured phenotypic selection via seed set on two floral and four carbon uptake traits of female and hermaphrodite Lobelia siphilitica. Because females can reproduce only via seeds, which are costlier than pollen, we predicted that females with smaller flowers and enhanced carbon uptake would have higher fitness, resulting in either sex morph-specific directional selection or stabilizing selection for different optimal trait values in females and hermaphrodites. We found that directional selection on one carbon uptake trait differed between females and hermaphrodites. We did not detect significant stabilizing selection on traits of either sex morph. Our results provide little support for the hypothesis that sexual dimorphism in gynodioecious plants evolved in response to sex morph-specific selection.
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Affiliation(s)
- C M Caruso
- Department of Integrative Biology, University of Guelph, Guelph, ON, Canada.
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Lieberman HR, Caruso CM, Niro PJ, Adam GE, Kellogg MD, Nindl BC, Kramer FM. A double-blind, placebo-controlled test of 2 d of calorie deprivation: effects on cognition, activity, sleep, and interstitial glucose concentrations. Am J Clin Nutr 2008; 88:667-76. [PMID: 18779282 DOI: 10.1093/ajcn/88.3.667] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND Anecdotal information and limited research suggest that short-term caloric deprivation adversely affects cognition. However, this issue has not been studied using double-blind, placebo-controlled procedures, because the formulation of a calorie-deficient feeding regimen identical to one with calories is impossible using ordinary foods. Therefore, test meals varying in caloric content, but indistinguishable in sensory characteristics, were formulated using hydrocolloid-based gels as the principal structural component. OBJECTIVE The purpose of this study was to examine the effects of 2 d of near-total caloric deprivation on cognitive function, satiety, activity, sleep, and glucose concentrations in a controlled environment. DESIGN A double-blind, placebo-controlled crossover study of caloric deprivation was conduced in a controlled environment for 48 h. Cognitive function in 27 healthy young subjects was assessed repeatedly with standardized tests of vigilance, reaction time, learning, memory, logical reasoning, mood, and satiety. Wrist-worn monitors were used to assess ambulatory vigilance, activity, and sleep. Interstitial glucose concentrations were assessed continuously with a minimally invasive monitor. RESULTS When the subjects received the near calorie-free diets, mean calorie consumption totaled 1311 kJ (313 kcal) over the testing period. During the fully fed treatment sessions, the subjects consumed a mean of 9612 kJ/d (2294 kcal/d), which matched their individual, daily energy requirements. Satiety and interstitial glucose concentrations were lower during the calorie-deprived diet (P < 0.001) than during the fully fed diet. There were no detectable effects of calorie deprivation on any aspect of cognitive performance, ambulatory vigilance, activity, or sleep. The mood states assessed, including fatigue, were not affected by calorie deprivation. CONCLUSIONS Cognitive performance, activity, sleep, and mood are not adversely affected in healthy humans by 2 d of calorie-deprivation when the subjects and investigators are unaware of the calorie content of the treatments.
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Affiliation(s)
- Harris R Lieberman
- Military Nutrition Division, US Army Research Institute of Environmental Medicine, Natick, MA 01760-5007, USA.
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Abstract
Variation in population sex ratio can be influenced by natural selection on alternate sex phenotypes as well as nonselective mechanisms, such as genetic drift and founder effects. If natural selection contributes to variation in population sex ratio, then sex ratio should covary with resource availability or herbivory. With nonselective mechanisms, sex ratio should covary with population size. We estimated sex ratio, resource availability, herbivory and size of 53 populations of gynodioecious Lobelia siphilitica. Females were more common in populations with higher annual temperatures, lower soil moisture and lower predation on female fruits, consistent with sex-specific selection. Females were also more common in small populations, consistent with drift, inbreeding or founder effects. However, small populations occurred in areas with higher temperatures than large populations, suggesting that female frequencies in small populations could be caused by sex-specific selection. Both selective and nonselective mechanisms likely affect sex ratio variation in this gynodioecious species.
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Affiliation(s)
- C M Caruso
- Department of Integrative Biology, University of Guelph, Guelph, ON, Canada.
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McGraw SM, Bathalon GP, Caruso CM, Lieberman HR, Young AJ. Psychological Adaptation of Normal Weight and Overweight Women During Marine Corps Recruit Training. Med Sci Sports Exerc 2006. [DOI: 10.1249/00005768-200605001-01888] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Caruso CM, Maherali H, Sherrard M. Plasticity of physiology in Lobelia: testing for adaptation and constraint. Evolution 2006; 60:980-90. [PMID: 16817538] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Phenotypic plasticity is thought to be a major mechanism allowing sessile organisms such as plants to adapt to environmental heterogeneity. However, the adaptive value of many common plastic responses has not been tested by linking these responses to fitness. Even when plasticity is adaptive, costs of plasticity, such as the energy necessary to maintain regulatory pathways for plastic responses, may constrain its evolution. We used a greenhouse experiment to test whether plastic physiological responses to soil water availability (wet vs. dry conditions) were adaptive and/or costly in the congeneric wildflowers Lobelia cardinalis and L. siphilitica. Eight physiological traits related to carbon and water uptake were measured. Specific leaf area (SLA), photosynthetic rate (A), stomatal conductance (gs), and photosynthetic capacity (Amax) responded plastically to soil water availability in L. cardinalis. Plasticity in Amax was maladaptive, plasticity in A and g(s) was adaptive, and plasticity in SLA was adaptively neutral. The nature of adaptive plasticity in L. cardinalis, however, differed from previous studies. Lobelia cardinalis plants with more conservative water use, characterized by lower g(s), did not have higher fitness under drought conditions. Instead, well-watered L. cardinalis that had higher g(s) had higher fitness. Only Amax responded plastically to drought in L. siphilitica, and this response was adaptively neutral. We detected no costs of plasticity for any physiological trait in either L. cardinalis or L. siphilitica, suggesting that the evolution of plasticity in these traits would not be constrained by costs. Physiological responses to drought in plants are presumed to be adaptive, but our data suggest that much of this plasticity can be adaptively neutral or maladaptive.
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Affiliation(s)
- Christina M Caruso
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, Canada.
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Abstract
Many workers have demonstrated a genetic basis for variation in inflorescence traits, but this variation can also have an environmental component. Because flowering can incur significant water costs, I estimated plasticity of inflorescence traits of three populations of Lobelia siphilitica in response to drought. I manipulated soil water availability in the greenhouse and measured seven inflorescence traits. Under drought conditions, plants from one population flowered later and produced fewer flowers with shorter corollas and narrower landing pads. In contrast, the height of the flowering stalk decreased in response to drought in all three populations. Consequently, pollinator-mediated natural selection on these plastic traits may depend on soil water availability. Plastic responses differed between genotypes only for the height of the flowering stalk and the length of the corolla tube and only in one or two populations. This suggests that genotype × environment interactions would not limit the evolution of inflorescence traits in L. siphilitica. The strength and sign of phenotypic correlations among inflorescence traits did not respond plastically to drought, suggesting that indirect selection on inflorescence traits of L. siphilitica will not vary strongly with water availability. My results suggest that plasticity of inflorescence traits may influence their evolution, but the effects are population- and trait-specific.
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Affiliation(s)
- Christina M Caruso
- Department of Integrative Biology, University of Guelph, Guelph, Ontario N1G 2W1 Canada
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Caruso CM, Remington DLD, Ostergren KE. Variation in resource limitation of plant reproduction influences natural selection on floral traits of Asclepias syriaca. Oecologia 2005; 146:68-76. [PMID: 16028094 DOI: 10.1007/s00442-005-0183-4] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2004] [Accepted: 06/07/2005] [Indexed: 10/25/2022]
Abstract
The availability of both pollen and resources can influence natural selection on floral traits, but their relative importance in shaping floral evolution is unclear. We experimentally manipulated pollinator and resource (fertilizer and water) availability in the perennial wildflower Asclepias syriaca L. Nine floral traits, one male fitness component (number of pollinia removed), and two female fitness components (number of pollinia inserted and number of fruits initiated) were measured for plants in each of three treatments (unmanipulated control, decreased pollinator access, and resource supplementation). Although decreasing pollinators' access to flowers did result in fewer pollinia inserted and removed, fruit set and phenotypic selection on floral traits via female and male fitness did not differ from the control. In contrast, resource supplementation increased fruit set, and phenotypic selection on seven out of nine floral traits was stronger via female than male fitness, consistent with the prediction that selection via female fitness would be greater when reproduction was less resource-limited. Our results support the hypothesis that abiotic resource availability can influence floral evolution by altering gender-specific selection.
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Caruso CM, Maherali H, Mikulyuk A, Carlson K, Jackson RB. GENETIC VARIANCE AND COVARIANCE FOR PHYSIOLOGICAL TRAITS IN LOBELIA:ARE THERE CONSTRAINTS ON ADAPTIVE EVOLUTION? Evolution 2005. [DOI: 10.1111/j.0014-3820.2005.tb01756.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Caruso CM, Maherali H, Mikulyuk A, Carlson K, Jackson RB. Genetic variance and covariance for physiological traits in Lobelia: are there constraints on adaptive evolution? Evolution 2005; 59:826-37. [PMID: 15926692] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Physiological traits that control the uptake of carbon dioxide and loss of water are key determinants of plant growth and reproduction. Variation in these traits is often correlated with environmental gradients of water, light, and nutrients, suggesting that natural selection is the primary evolutionary mechanism responsible for physiological diversification. Responses to selection, however, can be constrained by the amount of standing genetic variation for physiological traits and genetic correlations between these traits. To examine the potential for constraint on adaptive evolution, we estimated the quantitative genetic basis of physiological trait variation in one population of each of two closely related species (Lobelia siphilitica and L. cardinalis). Restricted maximum likelihood analyses of greenhouse-grown half-sib families were used to estimate genetic variances and covariances for seven traits associated with carbon and water relations. We detected significant genetic variation for all traits in L. siphilitica, suggesting that carbon-gain and water-use traits could evolve in response to natural selection in this population. In particular, narrow-sense heritabilities for photosynthetic rate (A), stomatal conductance (gs), and water-use efficiency (WUE) in our L. siphilitica population were high relative to previous studies in other species. Although there was significant narrow-sense heritability for A in L. cardinalis, we detected little genetic variation for traits associated with water use (gs and WUE), suggesting that our population of this species may be unable to adapt to drier environments. Despite being tightly linked functionally, the genetic correlation between A and gs was not strong and significant in either population. Therefore, our L. siphilitica population would not be genetically constrained from evolving high A (and thus fixing more carbon for growth and reproduction) while also decreasing gs to limit water loss. However, a significant negative genetic correlation existed between WUE and plant size in L. siphilitica, suggesting that high WUE may be negatively associated with high fecundity. In contrast, our results suggest that any constraints on the evolution of photosynthetic and stomatal traits of L. cardinalis are caused primarily by a lack of genetic variation, rather than by genetic correlations between these functionally related traits.
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Affiliation(s)
- Christina M Caruso
- Department of Biology and Mathematics, Grinnell College, Grinnell, Iowa 50112, USA.
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Caruso CM, Maherali H, Mikulyuk A, Carlson K, Jackson RB. GENETIC VARIANCE AND COVARIANCE FOR PHYSIOLOGICAL TRAITS IN LOBELIA: ARE THERE CONSTRAINTS ON ADAPTIVE EVOLUTION? Evolution 2005. [DOI: 10.1554/04-501] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Abstract
Although pollinator-mediated natural selection has been measured on many floral traits and in many species, the extent to which selection is constrained from producing optimal floral phenotypes is less frequently studied. In particular, negative correlations between flower size and flower number are hypothesized to be a major constraint on the evolution of floral displays, yet few empirical studies have documented such a trade-off. To determine the potential for genetic constraints on the adaptive evolution of floral displays, I estimated the quantitative genetic basis of floral trait variation in two populations of Lobelia siphilitica. Restricted maximum likelihood (REML) analyses of greenhouse-grown half-sib families were used to estimate genetic variances and covariances for flower number and six measures of flower size. There was significant genetic variation for all seven floral traits in both populations. Flower number was negatively genetically correlated with four measures of flower size in one population and three measures in the other. When the genetic variance-covariance matrices were combined with field estimates of phenotypic selection gradients, the predicted multivariate evolutionary response was less than or opposite in sign to the selection gradient for flower number and five of six measures of flower size, suggesting genetic constraints on the evolution of these traits. More generally, my results indicate that the adaptive evolution of floral displays can be constrained by trade-offs between flower size and number, as has been assumed by many theoretical models of floral evolution.
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Affiliation(s)
- Christina M Caruso
- Departments of Biology and Mathematics, Grinnell College, Grinnell, Iowa 50112, USA.
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Caruso CM, Peterson SB, Ridley CE. Natural selection on floral traits of Lobelia (Lobeliaceae): spatial and temporal variation. Am J Bot 2003; 90:1333-1340. [PMID: 21659233 DOI: 10.3732/ajb.90.9.1333] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The strength and direction of natural selection on floral traits can vary spatially and temporally because of variation in the biotic and abiotic environment. High spatial variation in selection should lead to differentiation of floral traits among populations. In contrast, high temporal variation in selection should retard the evolution of population-specific floral phenotypes. To determine the relative importance of spatial vs. temporal variation in natural selection, we measured phenotypic selection on seven floral traits of the wildflowers Lobelia cardinalis and L. siphilitica in 1999 and 2000. Lobelia cardinalis experienced significant temporal variation in selection, whereas L. siphilitica experienced spatial variation in selection on the same traits. This variation in selection on floral traits was associated with spatial and temporal differences in the soil microenvironment. Although few studies of natural selection include spatial or temporal replicates, our results suggest that such replication is critical for understanding the distribution of phenotypes in nature.
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Affiliation(s)
- Christina M Caruso
- Departments of Biology and Mathematics, Grinnell College, Grinnell, Iowa 50112 USA
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Caruso CM, Maherali H, Jackson RB. Gender-specific floral and physiological traits: implications for the maintenance of females in gynodioecious Lobelia siphilitica. Oecologia 2003; 135:524-31. [PMID: 16228251 DOI: 10.1007/s00442-003-1199-2] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2002] [Accepted: 01/17/2003] [Indexed: 11/25/2022]
Abstract
A common gender dimorphism in angiosperms is gynodioecy, in which hermaphrodites and females co-occur. Females are at an inherent disadvantage because they can transmit their genes only through ovule production. One mechanism by which females can compensate for the loss of male function is by producing more seeds than hermaphrodites. As such, females should: (1) increase resource uptake to support higher seed production; and (2) allocate resources saved by the loss of male function to seed production. To test this hypothesis, we measured physiological and floral traits of gynodioecious Lobelia siphilitica, controlling for both environmental and genetic variation through a comparison of greenhouse-grown siblings. Pre-reproductive females had 14% higher area-based (Z=2.14; P=0.04) and 32% higher mass-based (Z=1.96; P=0.05) photosynthetic rate than hermaphrodites, suggesting that they have increased carbon acquisition by altering photosynthetic physiology. Female L. siphilitica produced flowers with 4-8% smaller corollas than hermaphrodites (all P<0.05), suggesting that females allocate resources away from floral structures used for pollinator attraction. The genetic correlation between genders for four floral and four physiological traits was significantly less than one but greater than zero, indicating that the evolution of gender dimorphism in response to sex-differential selection will be constrained. The allocation of resources saved by the loss of male function has been viewed as the most important mechanism allowing females of gynodioecious species to support higher seed production. Our data suggest that increased resource acquisition by females at pre-reproductive stages can also contribute to the maintenance of gender dimorphism in gynodioecious species.
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Affiliation(s)
- Christina M Caruso
- Departments of Biology and Mathematics, Grinnell College, Grinnell, IA 50112, USA.
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Abstract
Although rarely tested, it is often assumed that interspecific competition results in the divergence of traits related to resource use. Using a plant-pollinator system as a model, I tested the prediction the presence of a competitor for pollination influences the strength and/or direction of pollinator-mediated selection on floral traits. I measured phenotypic selection via female fitness on five floral traits of Ipomopsis aggregata in seven populations. Four contained only conspecifics (I only) and three also contained the competitor Castilleja linariaefolia (C + I). Directional selection via fruits/plant and conspecific pollen deposited/flower on corolla length was positive and significantly stronger in C + I populations. This difference in selection was apparently driven by interpopulation variation in the degree to which reproduction of I. aggregata was pollen limited. Consistent with expectations of interspecific competition, I. aggregata plants in C + I populations received less conspecific pollen per flower and set fewer seeds per fruit and fruits per plant than those in I only populations. Ipomopsis aggregata's corollas were also significantly longer in C + I populations, suggesting that there had been a response to a similar selective regime in past generations. Phenotypic correlations between corolla length and width, which determine the variation in I. aggregata's flower shape, were significantly weaker in C + I populations. These data suggest that competition for pollination can influence the strength of selection on and patterns of correlations among floral traits of I. aggregata. If I. aggregata populations with and without competitors for pollination are linked by gene flow, then measuring selection in competitive and noncompetitive environments maybe necessary to accurately predict how floral traits will evolve.
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Affiliation(s)
- C M Caruso
- Department of Ecology, Ethology, and Evolution, University of Illinois at Urbana-Champaign, 61820, USA.
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Caruso CM, Alfaro M. Interspecific pollen transfer as a mechanism of competition: effect of Castilleja linariaefolia pollen on seed set of Ipomopsis aggregata. ACTA ACUST UNITED AC 2000. [DOI: 10.1139/b00-034] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We investigated whether the deposition of Castilleja linariaefolia (Pursh) V. Grant pollen on flowers of Ipomopsis aggregata (Benth.) in DC. reduced I. aggregata's seed set. Ipomopsis flowers were hand-pollinated with either pure conspecific pollen (the control) or with C. linariaefolia pollen applied prior to, simultaneously with, or following conspecific pollen. Flowers that were simultaneously given C. linariaefolia and I. aggregata pollen received 39% less conspecific pollen than flowers in the control, but did not set fewer seeds per fruit. Flowers that were given C. linariaefolia pollen first received 30% less conspecific pollen and set 38% fewer seeds per fruit than the control. These results suggest that there is a priority effect; deposition of C. linariaefolia pollen on I. aggregata flowers results in competition, but only when C. linariaefolia pollen is deposited first. Unlike pollen of another competitor of I. aggregata (Delphinium nelsonii Greene. Per.), C. linariaefolia pollen caused competition without inducing an increased rate of stigma closure. Only 12% of I. aggregata's stigmas closed when C. linariaefolia pollen was deposited, and seed set of I. aggregata was reduced relative to the control whether their stigmas closed or not. The low rate at which C. linariaefolia pollen induces closure of I. aggregata's stigmas could be an adaptation to reduce the negative effects of competition.Key words: Castilleja linariaefolia, competition, hand pollination, hummingbirds, Ipomopsis aggregata, pollination.
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