Biology subjects

Acker, P.

Publications and source records attributed to Acker, P..

5 recordsLinked to original sources

bioRxiv2026

Conceptualising and quantifying phenological plasticity through latent responses to seasonal environmental progression

Quantifying how individuals adjust the seasonal timings of life-history events (i.e. their phenology) in response to seasonal environmental conditions is fundamental to predicting impacts of changing seasonality. However, the current standard approach of inferring phenological responses by directly analysing observed event dates relies on foundational assumptions that could be invalidated by changing seasonality, and excludes individuals that do not express focal events, potentially generating misleading inferences. To overcome these limitations, we devised a Phenological Threshold Model (PTM) that conceptualizes phenological events as switches between discrete life-history states and primarily estimates variation in underlying latent dynamic responses to seasonal progression, from which event dates secondarily arise. We demonstrate that the PTM can accurately retrieve simulated parameter values, including given incomplete seasonal field observations. Application to multi-year data on annual breeding in black-legged kittiwakes (Rissa tridactyla) demonstrated substantial among-individual variation in latent responses to seasonally varying environmental drivers, and associated daily probabilities that individuals will initiate breeding, revealing how annual distributions of breeding dates and proportions of non-breeders jointly arise. We thereby formalise a new conceptual and statistical framework for quantifying the potential for, and constraints on, rapid plastic and micro-evolutionary changes in phenology in changing seasonal climatic and environmental regimes.

ecology↗

bioRxiv2026

Extreme climatic events shape adaptive potential by altering genetic variance for adult survival in a wild population

Extreme climatic events (ECEs) could potentially induce episodes of rapid adaptive evolution, altering the evolutionary trajectories and viability of wild populations experiencing increasingly stochastic environments. Adaptive potential stems substantially from additive genetic variance (V) in survival. However, the degree to which ECEs impact this variance, and the resulting evolutionary implications, have not been fully conceptualised or quantified in nature. These aims are highly challenging because underlying genetic and environmental variances have fundamentally non-linear effects on the dichotomous phenotypic outcome of survival versus death, while substantial data are required for estimation. We present a conceptual and analytical framework that formalises biological hypotheses for how V depends on environmental severity, how such dependences are reshaped by non-linear genotype-environment-phenotype relationships and demographic structure, and the implications for evolutionary responses. We then use 25 years of survival and pedigree data from European shags (Gulosus aristotelis) to decompose variance in adult survival across diverse environmental conditions including ECEs. Using a capture-recapture animal model, we demonstrate non-negligible V underlying adult survival across all years combined, implying notable adaptive potential. Yet, partitioning by environmental severity revealed substantial V in good years with high survival but negligible V in bad years with ECE-induced low survival, implying a genotype-by-environment interaction that constrains adaptive potential under severe conditions. However, scale transformations showed how the non-linear genotype-environment-phenotype relationship can distort or even reverse such patterns, by reducing the extent to which V is phenotypically expressed in good conditions with high mean survival and amplifying it in more severe conditions with lower mean survival. Evolutionary responses to severe conditions could consequently be non-negligible even given small underlying V. We thereby demonstrate how ECEs can reshape adaptive potential, highlighting the need to integrate impacts of environmental severity on genetic variation in fitness components into predictions of population resilience under climate change.

evolutionary biology↗

bioRxiv2026

Differing components of plasticity in quantitative genetic threshold traits cause diverging eco-evolutionary responses to spatio-seasonal environmental deterioration

Eco-evolutionary responses to long-term environmental deteriorations will fundamentally depend on interactions between plasticity and evolution of life-history traits that shape population dynamics. Counter-intuitive evolutionary and (meta)population dynamics could arise when different components of individual-specific and/or shared site-specific developmental and labile plasticity affect traits with intrinsically non-linear genotype-environment-phenotype relationships, especially given density-dependent fitness outcomes. Frequency-dependent evolutionary responses could then emerge, but resulting eco-evolutionary dynamics and outcomes have rarely been considered. By modelling a partially-migratory metapopulation encompassing facultative seasonal migration versus residence formulated as a quantitative genetic threshold trait, we show how different forms of plasticity in liability to migrate interact with spatio-seasonal metapopulation dynamics to generate divergent eco-evolutionary responses to spatially restricted environmental deterioration. Temporary and permanent individual-specific environmental effects induced faster evolutionary recovery than might simply be expected, by revealing cryptic genetic variation and allowing adaptive phenotypic changes through repeated episodes of selective disappearance. Conversely, shared subpopulation-specific environmental effects caused among-year variation in phenotype frequencies, impeding evolutionary responses to the extent that migratory metapopulation connectivity was ultimately eradicated. We thereby reveal key principles of how structurally different forms of plasticity in a dichotomous quantitative genetic trait can induce complex eco-evolutionary dynamics, culminating in differing degrees of evolutionary rescue versus constraint.

evolutionary biology↗

bioRxiv2023

Eco-evolutionary dynamics of partially migratory metapopulations in spatially and seasonally varying environments

Predicting population responses to environmental changes requires understanding interactions among environmentally induced phenotypic variation, selection, demography and genetic variation, and thereby predicting eco-evolutionary dynamics emerging across diverse temporal and spatial scales. Partially migratory metapopulations (PMMPs), featuring seasonal coexistence of resident and migrant individuals across multiple spatially distinct subpopulations, have clear potential for complex spatio-seasonal eco-evolutionary dynamics through impacts of selection on migration on spatial population dynamics, and feedbacks resulting from ongoing micro-evolution. However, the key genetic and environmental conditions that maintain migratory polymorphisms, and eco-evolutionary dynamics of PMMPs under stochastic environmental variation and strong seasonal perturbations, have not yet been resolved. Accordingly, we present a general individual-based model that tracks eco-evolutionary dynamics in PMMPs inhabiting spatially structured, seasonally varying landscapes, with migration formulated as a quantitative genetic threshold trait. Our simulations show that such genetic and landscape structures, which commonly occur in nature, can readily produce a variety of stable partially migratory systems given diverse regimes of spatio-seasonal environmental variation. Typically, partial migration is maintained whenever sites differ in non-breeding season suitability resulting from variation in density-dependence, causing ideal free non-breeding distributions where residents and migrants occur with frequencies that generate similar survival probabilities. Yet, stable partial migration can also arise without any fixed differences in non-breeding season density-dependence among sites, and even without density-dependence at all, through risk-spreading given sufficiently large stochastic environmental fluctuations among sites and years. Finally, we show that local non-breeding season mortality events, as could result from extreme climatic events, can generate eco-evolutionary dynamics that ripple out to affect breeding and non-breeding season space use of subpopulations throughout the PMMP, on both short and longer timeframes. Such effects result from spatially divergent selection on both the occurrence and destinations of migration. Our model thus shows how facultative seasonal migration can act as a key mediator of eco-evolutionary dynamics in spatially and seasonally structured environments, providing key steps towards predicting responses of natural partially migratory populations to ongoing changes in spatio-seasonal patterns of environmental variation.

evolutionary biology↗

bioRxiv2022

Components of micro-evolutionary and phenotypic change in seasonal migration versus residence in a wild population

Dissecting joint micro-evolutionary and plastic responses to environmental perturbations fundamentally requires quantifying interacting components of genetic and environmental variation underlying expression of key traits. This ambition is particularly challenging for phenotypically discrete traits where multiscale decompositions are required to handle non-linear transformations of underlying genetic and environmental variation into phenotypic variation, especially when effects have to be estimated from incomplete field observations. We devised a novel joint multistate capture-recapture and quantitative genetic animal model, and fitted this model to full-annual-cycle resighting data from partially migratory European shags (Gulosus aristotelis) to estimate key components of genetic, environmental and phenotypic variance in the ecologically critical discrete trait of seasonal migration versus residence. We demonstrate non-trivial additive genetic variance in latent liability for migration, resulting in estimated micro-evolutionary responses following two episodes of strong survival selection. Yet, underlying additive genetic effects interacted with substantial permanent individual and temporary environmental effects to generate complex non-additive effects, causing large intrinsic gene-by-environment interaction variance in phenotypic expression. Our findings reveal how temporal dynamics of seasonal migration result from combinations of instantaneous micro-evolution and within-individual phenotypic inertia, and highlight how plastic phenotypic variation could expose cryptic genetic variation underlying discrete traits to complex forms of selection.

evolutionary biology↗