Life‐history evolution in response to changes in metapopulation structure in an arthropod herbivore

Abstract

International audienceThe persistence and dynamics of populations largely depend on the way they are configured and integrated into space and the ensuing eco-evolutionary dynamics. * We manipulated spatial and temporal variation in patch size in replicated experimental metapopulations of the herbivore mite Tetranychus urticae and followed evolutionary dynamics over approximately 30 generations. * A significant divergence in life-history traits, physiological endpoints and gene expression was recorded in the spatially and spatiotemporally variable metapopulation, but also a remarkable convergence relative to the stable reference metapopulation in traits related to size and fecundity and in its transcriptional regulation. * The observed evolutionary dynamics are tightly linked to demographic changes, more specifically frequent episodes of resource shortage that increased the reproductive performance of mites on tomato, a challenging host plant. This points towards a general, adaptive stress response in stable spatial variable and spatiotemporal variable metapopulations that pre-adapts a herbivore arthropod to novel environmental stressor

The importance and adaptive value of life history evolution for metapopulation dynamics

“…We build on earlier experimental work demonstrating a profound impact of metapopulation structure on both local and metapopulation-level demography, life-history evolution and gene expression in the spider mite Tetranychus urticae [18,39]. In short, we found divergent multivariate trait evolution in metapopulations with either stable patches of variable size (mainland-island metapopulations) or with patch size varying in space and time (classical metapopulation) relative to metapopulations with equal and temporally stable patch sizes (patchy metapopulation).…”

“…The model is individual-based and simulates mite development and population dynamics as in the experiments [18,39] on a daily basis for 1200 days, after an initialization phase of 100 time steps. In the experimental evolution [18,39], mites from one genetically variable source population were either placed in a metapopulation consisting of nine equally sized patches (patchy metapopulation), nine patches with the same amount of resources randomly assigned to each patch every week until the metapopulation carrying capacity was reached (classical metapopulation), or six patches of which three were of double size (mainland-island metapopulation).…”

“…In the experimental evolution [18,39], mites from one genetically variable source population were either placed in a metapopulation consisting of nine equally sized patches (patchy metapopulation), nine patches with the same amount of resources randomly assigned to each patch every week until the metapopulation carrying capacity was reached (classical metapopulation), or six patches of which three were of double size (mainland-island metapopulation). Patches consist of leaves of 20 cm², or 40 cm² for the large patches in the mainland-island metapopulations.…”

“…The metapopulation-level carrying capacity as defined by the total availability of leaf surface over subsequent generations was thus identical among treatments. The evolved traits, as determined at the end of the experimental evolution (see [18] and schematic overview in Table 1) were used to parameterize the model. Individuals carry alleles that determine survival rate during development, age at maturity, longevity, probability of being female (sex ratio) .…”

“…While dispersal is a central trait in life history [5], other traits have been documented to evolve in parallel, and often in unpredictable ways [15,16]. Few empirical studies tested theoretical predictions beyond dispersal evolution, but recent work provides evidence of multivariate life-history evolution in metapopulations [17,18]. These studies suggest that fitness can be maximized through the optimization of different trait combinations.…”