Abstract
Changes in the seasonal timing of life history events are documented effects of climate change. We used a general model to study how dispersal and competitive interactions affect eco-evolutionary responses to changes in the temporal distribution of resources over the season. Specifically, we modeled adaptation of the timing of reproduction and population dynamic responses in two competing populations that disperse between two habitats characterized by an early and late resource peak. We investigated three scenarios of environmental change: (1) food peaks advance in both habitats, (2) in the late habitat only and (3) in the early habitat only. At low dispersal rates the evolutionarily stable timing of reproduction closely matched the local resource peak and the environmental change typically caused population decline. Larger dispersal rates rendered less intuitive eco-evolutionary population responses. First, dispersal caused mismatch between evolutionarily stable timing of reproduction and local resource peaks and as a result, reproductive output for subpopulations could increase as well as decrease when resource availability underwent temporal shifts. Second, population responses were contingent on competition between populations. This could accelerate population declines and cause extinctions or even reverse population trends from negative to positive compared to the low dispersal case. When dispersal rate was large and the early resource peak was advanced available niche space was reduced. Hence, even when a population survived the environmental change and obtained positive equilibrium population density, subsequent adaptation of competing populations could drive it to extinction due to convergent evolution and competitive exclusion. These results shed new light on the role of competition and dispersal for the evolution of timing of life history events and provide guidelines for understanding short and long-term population response to climate change.
Highlights
The importance of the timing of seasonal activities in relation to abiotic conditions and ecological interactions, e.g. in relation to food resources, has been empirically demonstrated in several taxa (Thomas et al 2001; Visser and Both 2005; Inouye 2008)
One can contrast our results with a scenario in which dispersal is absent and where adaptation of timing of reproduction depends on local resource availability only
Our results show that when taking spatial structure into account, competitive interactions and dispersal, we can expect much more variation in the long- and short-term responses to shifted resource phenology than when considering the temporal matching between resource availability and timing of reproduction alone
Summary
The importance of the timing of seasonal activities in relation to abiotic conditions and ecological interactions, e.g. in relation to food resources, has been empirically demonstrated in several taxa (Thomas et al 2001; Visser and Both 2005; Inouye 2008). Following the adaptive dynamics framework (Geritz et al 1998) the resident populations are assumed to be at equilibrium between invasion attempts, and we study only the growth of a rare mutant population that does not influence the competitive environment In this model, this means that the reproductive output depends on the resident population densities (N*) only. The settings of the model parameters determine the evolutionary stable trait distribution as well as the equilibrium population densities In essence both evolutionary and ecological equilibrium can be understood through factors such as differences among habitats and dispersal propensity and niche width of the model organisms. We investigate the responses in population density and the adaptive changes in trait values assuming three different scenarios of temporal shifts in resource availability in the form of (instantaneous) shifts of the resource distributions along the time axis (Fig. 3, top). Our measure of long-term evolutionary responses were changes in the ESS values
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