Can individual variation in phenotypic plasticity enhance population viability?

Abstract

a b s t r a c tIn response to climatic and other sources of environmental variation, individuals within a population may adjust their behavioral, morphological or physiological responses to varying environmental conditions through phenotypic plasticity. In seasonal environments, time constraints related to seasonality, as well as variation in climatic factors, may affect body mass growth rates. To cope with the consequences of a harsh period, individuals may, for example, compensate for lost body mass by accelerating their growth rate in the following period. Phenotypically plastic responses like this can, therefore, directly affect body mass, which may affect individual fitness and, ultimately, population dynamics. Here, we use a well-studied population of yellow-bellied marmots, Marmota flaviventris, in Colorado to parametrize and develop an individual-based model (IBM) to investigate how phenotypically plastic responses in body mass growth rate may compensate for an individual's bad start after a harsh period (compensatory growth), and to explore whether individual variation in compensatory growth favors population persistence under less favorable climatic scenarios. A simulation model that allowed marmots with a body mass less than the population's average body mass to compensate their growth provided the best match with observed population sizes, suggesting the importance of trade-offs in population dynamics. We also found that compensatory growth plays an important role in decreasing the probability of extinction under both less favorable colder and random climate scenarios. Our results lead to a deeper understanding of the mechanisms that govern population fluctuations and highlight the importance of quantifying the fitness cost of phenotypically plastic responses.

Assessing seasonal demographic covariation to understand environmental‐change impacts on a hibernating mammal

“…Aside from the effects of environmental quality, our models are consistent with previous findings on the importance of body mass and stage on yellow‐bellied marmot demography (Ozgul et al, ; Maldonado‐Chaparro et al, ). The most parsimonious GLMMs (Table .1) showed a positive effect of mass on all demographic processes, with the weakest effect of mass on summer survival (θ S ) of reproductive adults.…”

“…Unlike the effects of seasonal survival and reproduction, trait transitions between seasons had a smaller effect on annual population dynamics, even if winter mass changes were mediated by environmental quality. These relatively small effects are likely due to the fact that marmots compensate for winter mass loss with increased growth in the summer, creating a zero‐net effect on annual trait change (Maldonado‐Chaparro et al, , ). Although the strength of compensatory effects may differ within seasons or among life‐history stages (Monclús et al, ), such effects are common in rodents and other species that have a short window for mass gain (Morgan & Metcalfe, ; Orizaola et al, ), and highlight how assessing seasonal dynamics can provide a mechanistic understanding of population‐level global‐change effects (Bassar et al, ).…”

“…Climatic conditions in both winter and summer have been shown to influence reproduction and survival in the subsequent season (Van Vuren & Armitage, ; Lenihan & Van Vuren, ). In addition, predation is the major cause of death in the active summer season (Van Vuren, ; Maldonado‐Chaparro et al, ) and may be particularly severe shortly before (Bryant & Page, ) or after hibernation (Armitage, ), especially in years with heavy snow (Blumstein, pers. obs.).…”

“…demographic processes) as a function of stage and body mass – or mother's mass in the case of juvenile mass – at the beginning of a season, using a Bayesian modelling framework (Table ; Supporting Material S1). All mass estimates were cube‐root transformed to stabilize the variance and improve the normality of the residuals in the Gaussian submodels (Maldonado‐Chaparro et al, ). We fitted all demographic‐process submodels as generalized linear mixed effects models (GLMMs).…”

Consistency in boldness expression varies with ecological context in a jumping spider

“…Animals that tend to respond in a fixed way may benefit in contexts that require a consistent and fast response, while animals that are highly plastic in their behaviours may benefit in contexts that require a specific response and the cost of delay is low. Given the fact that a population's environment will likely fluctuate over time, individual variation in behavioural response may benefit the performance and persistence of the population (Dingemanse & Wolf, ; Maldonado‐Chaparro, Read, & Blumstein, ; Reed, Waples, Schindler, Hard, & Kinnison, ).…”