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1. Parental investment in the Columbian ground squirrel: empirical tests of sex allocation models

Author

F. Stephen Dobson, Jan O. Murie, Thibaut Barra, Vincent A. Viblanc, Claire Saraux, Département Ecologie, Physiologie et Ethologie (DEPE-IPHC), Institut Pluridisciplinaire Hubert Curien (IPHC), Université de Strasbourg (UNISTRA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Department of Biological Sciences, University of Alberta, and Auburn University (AU)

Subjects
Male, 0106 biological sciences, Offspring, [SDV]Life Sciences [q-bio], Kin selection, Biology, 010603 evolutionary biology, 01 natural sciences, 03 medical and health sciences, Trivers–Willard hypothesis, Animals, Sex Ratio, Selection, Genetic, Parental investment, Ecology, Evolution, Behavior and Systematics, Sex allocation, 030304 developmental biology, 0303 health sciences, Ecology, Reproduction, Sciuridae, Biological Evolution, Sexual selection, Female, Paternal care, Sex ratio, Demography
Abstract

Parental allocation of resources into male or female offspring and differences in the balance of offspring sexes in natural populations are central research topics in evolutionary ecology. Fisher (Fisher, R. A. 1930. The genetical theory of natural selection, Clarendon Press, Oxford, UK) identified frequency-dependent selection as the mechanism responsible for an equal investment in the sexes of offspring at the end of parental care. Three main theories have been proposed for explaining departures from Fisherian sex ratios in light of variation in environmental (social) and individual (maternal condition) characteristics. The Trivers-Willard model (Trivers, R., and D. Willard. 1973. Natural selection of parental ability to vary the sex ratio of offspring. Science 179:90-92) of male-biased sex allocation by mothers in the best body condition is based on the competitive ability of male offspring for future access to mates and thus superior reproduction. The local resource competition model is based on competitive interactions in matrilines, as occur in many mammal species, where producing sons reduces future intrasexual competition with daughters. A final model invokes advantages of maintaining matrilines for philopatric females, despite any increased competition among females. We used 29 yr of pedigree and demographic data to evaluate these hypotheses in the Colombian ground squirrel (Urocitellus columbianus), a semisocial species characterized by strong female philopatry. Overall, male offspring were heavier than female offspring at birth and at weaning, suggesting a higher production cost. With more local kin present, mothers in the best condition biased their offspring sex ratio in favor of males, and mothers in poor condition biased offspring sex ratio in favor of females. Without co-breeding close kin, the pattern was reversed, with mothers in the best condition producing more daughters, and mothers in poor condition producing more sons. Our results do not provide strong support for any of the single-factor models of allocation to the sexes of offspring, but rather suggest combined influences of relative maternal condition and matriline dominance on offspring sex ratio.

Published
2021
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2. Assessing the Potential for Mobilization of Old Soil Carbon After Permafrost Thaw: A Synthesis of 14 C Measurements From the Northern Permafrost Region

Author

Peter A. Raymond, Jocelyn Egan, Suzanne E. Tank, Iain P. Hartley, Claudia I. Czimczik, Jonathan A. O'Donnell, Massimo Lupascu, Susan M. Natali, Mark H. Garnett, Alison M. Hoyt, Edward A. G. Schuur, Benjamin W. Abbott, Andrew J. Tanentzap, Jeffrey P. Chanton, Laure Gandois, David Olefeldt, Katey M. Walter Anthony, Cristian Estop-Aragonés, Merritt R. Turetsky, Joshua F. Dean, Olefeldt, David, 1 Department of Renewable Resources University of Alberta Edmonton Canada, Abbott, Benjamin W., 3 Department of Plant and Wildlife Sciences Brigham Young University Provo UT USA, Chanton, Jeffrey P., 4 Department of Earth Ocean and Atmospheric Science Florida State University Tallahassee FL USA, Czimczik, Claudia I., 5 Department of Earth System Science University of California Irvine CA USA, Dean, Joshua F., 6 School of Environmental Sciences University of Liverpool Liverpool UK, Egan, Jocelyn E., 7 Department of Earth Sciences Dalhousie University Halifax Canada, Gandois, Laure, 8 Laboratoire Ecologie Fonctionnelle et Environnement Université de Toulouse, CNRS Toulouse France, Garnett, Mark H., 9 NEIF Radiocarbon Laboratory, Scottish Enterprise Technology Park, Rankine Avenue East Kilbride UK, Hartley, Iain P., 10 Geography, College of Life and Environmental Sciences University of Exeter Exeter UK, Hoyt, Alison, 11 Max Planck Institute for Biogeochemistry Jena Germany, Lupascu, Massimo, 12 Department of Geography National University of Singapore Singapore Singapore, Natali, Susan M., 13 Woodwell Climate Research Center Falmouth MA USA, O'Donnell, Jonathan A., 14 National Park Service, Arctic Network Anchorage AK USA, Raymond, Peter A., 15 Yale School of Forestry and Environmental Studies New Haven CT USA, Tanentzap, Andrew J., 16 Ecosystems and Global Change Group, Department of Plant Sciences University of Cambridge Cambridge UK, Tank, Suzanne E., 17 Department of Biological Sciences University of Alberta Edmonton Canada, Schuur, Edward A. G., 18 Department of Biological Sciences Northern Arizona University Flagstaff AZ USA, Turetsky, Merritt, 19 Department of Integrative Biology University of Guelph Guelph Canada, Anthony, Katey Walter, 20 Water and Environmental Research Center University of Alaska Fairbanks Fairbanks AK USA, Laboratoire Ecologie Fonctionnelle et Environnement (LEFE), Institut Ecologie et Environnement (INEE), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT), Laboratoire Ecologie Fonctionnelle et Environnement (ECOLAB), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), and Université Fédérale Toulouse Midi-Pyrénées

Subjects
particulate organic carbon, 0106 biological sciences, Atmospheric Science, 551.9, Peat, 010504 meteorology & atmospheric sciences, permafrost thaw, [SDE.MCG]Environmental Sciences/Global Changes, Permafrost, 01 natural sciences, Thermokarst, Dissolved organic carbon, Environmental Chemistry, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, General Environmental Science, Global and Planetary Change, geography, geography.geographical_feature_category, methane, 010604 marine biology & hydrobiology, carbon dioxide, Soil carbon, 15. Life on land, dissolved organic carbon, Tundra, 13. Climate action, [SDE]Environmental Sciences, Soil water, radiocarbon, Erosion, Environmental science, Physical geography
Abstract

The magnitude of future emissions of greenhouse gases from the northern permafrost region depends crucially on the mineralization of soil organic carbon (SOC) that has accumulated over millennia in these perennially frozen soils. Many recent studies have used radiocarbon (14C) to quantify the release of this “old” SOC as CO2 or CH4 to the atmosphere or as dissolved and particulate organic carbon (DOC and POC) to surface waters. We compiled ~1,900 14C measurements from 51 sites in the northern permafrost region to assess the vulnerability of thawing SOC in tundra, forest, peatland, lake, and river ecosystems. We found that growing season soil 14C‐CO2 emissions generally had a modern (post‐1950s) signature, but that well‐drained, oxic soils had increased CO2 emissions derived from older sources following recent thaw. The age of CO2 and CH4 emitted from lakes depended primarily on the age and quantity of SOC in sediments and on the mode of emission, and indicated substantial losses of previously frozen SOC from actively expanding thermokarst lakes. Increased fluvial export of aged DOC and POC occurred from sites where permafrost thaw caused soil thermal erosion. There was limited evidence supporting release of previously frozen SOC as CO2, CH4, and DOC from thawing peatlands with anoxic soils. This synthesis thus suggests widespread but not universal release of permafrost SOC following thaw. We show that different definitions of “old” sources among studies hamper the comparison of vulnerability of permafrost SOC across ecosystems and disturbances. We also highlight opportunities for future 14C studies in the permafrost region., Key Points: We compiled ~1,900 14C measurements of CO2, CH4, DOC, and POC from the northern permafrost region. Old carbon release increases in thawed oxic soils (CO2), thermokarst lakes (CH4 and CO2), and headwaters with thermal erosion (DOC and POC). Simultaneous and year‐long 14C analyses of CO2, CH4, DOC, and POC are needed to assess the vulnerability of permafrost carbon across ecosystems., EC | H2020 | H2020 Priority Excellent Science | H2020 European Research Council (ERC) http://dx.doi.org/10.13039/100010663, Gouvernement du Canada | Natural Sciences and Engineering Research Council of Canada (NSERC) http://dx.doi.org/10.13039/501100000038, National Science Foundation (NSF) http://dx.doi.org/10.13039/100000001

Published
2020
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