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  • Articles  (4)
  • Individual quality  (2)
  • Population growth rate  (2)
  • 1
    Publication Date: 2022-05-25
    Description: Author Posting. © University of Chicago, 2010. This article is posted here by permission of University of Chicago for personal use, not for redistribution. The definitive version was published in American Naturalist 175 (2010): 739-752, doi:10.1086/652436.
    Description: We present a new approach to modeling two‐sex populations, using periodic, nonlinear two‐sex matrix models. The models project the population growth rate, the population structure, and any ratio of interest (e.g., operational sex ratio). The periodic formulation permits inclusion of highly seasonal behavioral events. A periodic product of the seasonal matrices describes annual population dynamics. The model is nonlinear because mating probability depends on the structure of the population. To study how the vital rates influence population growth rate, population structure, and operational sex ratio, we used sensitivity analysis of frequency‐dependent nonlinear models. In nonlinear two‐sex models the vital rates affect growth rate directly and also indirectly through effects on the population structure. The indirect effects can sometimes overwhelm the direct effects and are revealed only by nonlinear analysis. We find that the sensitivity of the population growth rate to female survival is negative for the emperor penguin, a species with highly seasonal breeding behavior. This result could not occur in linear models because changes in population structure have no effect on per capita reproduction. Our approach is applicable to ecological and evolutionary studies of any species in which males and females interact in a seasonal environment.
    Description: H.C. acknowledges support from the National Science Foundation (DEB-0343820 and DEB-0816514) and the Ocean Life Institute and the hospitality of the Max Planck Institute for Demographic Research.
    Keywords: Two‐sex periodic matrix model ; Population structure ; Population growth rate ; Mating systems ; Sex ratio ; Emperor penguin
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 2
    Publication Date: 2022-05-25
    Description: © The Author(s), 2014. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Journal of Ecology 103 (2015): 202–218, doi:10.1111/1365-2745.12334.
    Description: Schedules of survival, growth and reproduction are key life-history traits. Data on how these traits vary among species and populations are fundamental to our understanding of the ecological conditions that have shaped plant evolution. Because these demographic schedules determine population growth or decline, such data help us understand how different biomes shape plant ecology, how plant populations and communities respond to global change and how to develop successful management tools for endangered or invasive species. Matrix population models summarize the life cycle components of survival, growth and reproduction, while explicitly acknowledging heterogeneity among classes of individuals in the population. Matrix models have comparable structures, and their emergent measures of population dynamics, such as population growth rate or mean life expectancy, have direct biological interpretations, facilitating comparisons among populations and species. Thousands of plant matrix population models have been parameterized from empirical data, but they are largely dispersed through peer-reviewed and grey literature, and thus remain inaccessible for synthetic analysis. Here, we introduce the compadre Plant Matrix Database version 3.0, an open-source online repository containing 468 studies from 598 species world-wide (672 species hits, when accounting for species studied in more than one source), with a total of 5621 matrices. compadre also contains relevant ancillary information (e.g. ecoregion, growth form, taxonomy, phylogeny) that facilitates interpretation of the numerous demographic metrics that can be derived from the matrices. Large collections of data allow broad questions to be addressed at the global scale, for example, in genetics (genbank), functional plant ecology (try, bien, d3) and grassland community ecology (nutnet). Here, we present compadre, a similarly data-rich and ecologically relevant resource for plant demography. Open access to this information, its frequent updates and its integration with other online resources will allow researchers to address timely and important ecological and evolutionary questions.
    Keywords: Big data ; Comparative approach ; Elasticity ; Matrix population model ; Open access ; Plant population and community dynamics ; Population growth rate ; Sensitivity ; Transient dynamics
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 3
    Publication Date: 2023-02-21
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Jenouvrier, S., Aubry, L., van Daalen, S., Barbraud, C., Weimerskirch, H., & Caswell, H. When the going gets tough, the tough get going: effect of extreme climate on an Antarctic seabird’s life history. Ecology Letters, 25, (2022): 2120– 2131, https://doi.org/10.1111/ele.14076.
    Description: Individuals differ in many ways. Most produce few offspring; a handful produce many. Some die early; others live to old age. It is tempting to attribute these differences in outcomes to differences in individual traits, and thus in the demographic rates experienced. However, there is more to individual variation than meets the eye of the biologist. Even among individuals sharing identical traits, life history outcomes (life expectancy and lifetime reproduction) will vary due to individual stochasticity, that is to chance. Quantifying the contributions of heterogeneity and chance is essential to understand natural variability. Interindividual differences vary across environmental conditions, hence heterogeneity and stochasticity depend on environmental conditions. We show that favourable conditions increase the contributions of individual stochasticity, and reduce the contributions of heterogeneity, to variance in demographic outcomes in a seabird population. The opposite is true under poor conditions. This result has important consequence for understanding the ecology and evolution of life history strategies.
    Description: We acknowledge Institute Paul Emile Victor (Programme IPEV 109), and Terres Australes et Antarctiques Françaises for logistical and financial support in Terre Adélie. The study is a contribution to the Program EARLYLIFE funded by a European Research Council Advanced Grant under the European Community's Seven Framework Program FP7/2007-2013 (Grant Agreement ERC-2012-ADG_20120314 to Henri Weimerskirch), to the program SENSEI funded by the BNP Paribas Foundation, and to the Program INDSTOCH funded by ERC Advanced Grant 322989 to Hal Caswell. SJ acknowledges support from Ocean Life Institute and WHOI Unrestricted funds, and NSF projects DEB-1257545, OPP-1246407 and OPP-1840058.
    Keywords: Fixed heterogeneity ; Frailty ; Individual quality ; Individual stochasticity ; Unobserved individual heterogeneity ; SICs
    Repository Name: Woods Hole Open Access Server
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  • 4
    Publication Date: 2022-05-26
    Description: Author Posting. © The Author(s), 2017. This is the author's version of the work. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Journal of Animal Ecology 87 (2018): 212-222, doi:10.1111/1365-2656.12752.
    Description: Individuals are heterogeneous in many ways. Some of these differences are incorporated as individual states (e.g., age, size, breeding status) in population models. However, substantial amounts of heterogeneity may remain unaccounted for, due to genetic, maternal, or environmental factors. Such unobserved heterogeneity (UH) affects the behavior of heterogeneous cohorts via intra-cohort selection and contributes to inter-individual variance in demographic outcomes such as longevity and lifetime reproduction. Variance is also produced by individual stochasticity, due to random events in the life cycle of wild organisms, yet no study thus far has attempted to decompose the variance in demographic outcomes into contributions from unobserved heterogeneity and individual stochasticity for an animal population in the wild. We developed a stage-classified matrix population model for the Southern fulmar breeding on Ile des Pétrels, Antarctica. We applied multi-event, multi-state markrecapture methods to estimate a finite mixture model accounting for UH in all vital rates and Markov chain methods to calculate demographic outcomes. Finally, we partitioned the variance in demographic outcomes into contributions from unobserved heterogeneity and individual stochasticity. We identify three UH groups, differing substantially in longevity, lifetime reproductive output, age at first reproduction, and in the proportion of the life spent in each reproductive state. 14% of individuals at fledging have a delayed but high probability of recruitment and extended reproductive lifespan. 67% of individuals are less likely to reach adulthood, recruit late and skip breeding often but have the highest adult survival rate. 19% of individuals recruit early and attempt to breed often. They are likely to raise their offspring successfully, but experience a relatively short lifespan. Unobserved heterogeneity only explains a small fraction of the variances in longevity (5.9%), age at first reproduction (3.7%) and lifetime reproduction (22%). UH can affect the entire life cycle, including survival, development, and reproductive rates, with consequences over the lifetime of individuals and impacts on cohort dynamics. The respective role of unobserved heterogeneity versus individual stochasticity varies greatly among demographic outcomes. We discuss the implication of our finding for the gradient of life-history strategies observed among species and argue that individual differences should always be accounted for in demographic studies of wild populations.
    Description: We acknowledge Institute Paul Emile Victor (Programme IPEV 109), and Terres Australes et Antarctiques Françaises for for logistical and financial support in Terre Adélie. SJ acknowledges support from Ocean Life Institute and WHOI Unrestricted funds, and NSF projects DEB-1257545 and OPP-1246407.
    Keywords: Frailty ; Individual quality ; Latent ; Life expectancy ; Life time reproductive success
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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