Adaptation and Evolutionary Rescue in Metapopulations Experiencing Environmental Deterioration
Department of Biology, McGill University, 1205 ave Docteur Penfield, Montreal, Quebec H3A 1B1, Canada.Science (Impact Factor: 33.61). 06/2011; 332(6035):1327-30. DOI: 10.1126/science.1203105
It is not known whether evolution will usually be rapid enough to allow a species to adapt and persist in a deteriorating environment. We tracked the eco-evolutionary dynamics of metapopulations with a laboratory model system of yeast exposed to salt stress. Metapopulations experienced environmental deterioration at three different rates and their component populations were either unconnected or connected by local dispersal or by global dispersal. We found that adaptation was favored by gradual deterioration and local dispersal. After further abrupt deterioration, the frequency of evolutionary rescue depended on both the prior rate of deterioration and the rate of dispersal. Adaptation was surprisingly frequent and rapid in small peripheral populations. Thus, evolutionary dynamics affect both the persistence and the range of a species after environmental deterioration.
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- "Dormancy is a non-evolving state that is not expected to have any effect on subsequent adaptation. Dispersal may have a profound effect on the likelihood of rescue by allowing resistant alleles to move up a gradient of stress (Bell & Gonzalez 2011). If a population continues to grow in situ, as in our experiment, it may be progressively impaired by prior exposure to stress, even if individuals express a generalised stress response. "
ABSTRACT: Persistence by adaptation is called evolutionary rescue. Evolutionary rescue is more likely in populations that have been previously exposed to lower doses of the same stressor. Environmental fluctuations might also reduce the possibility of rescue, but little is known about the effect of evolutionary history on the likelihood of rescue. In this study, we hypothesised that the ubiquitous operation of generalised stress responses in many organisms increases the likelihood of rescue after exposure to other stressors. We tested this hypothesis with experimental populations that had been exposed to long-term starvation and were then selected on different, unrelated stressors. We found that prior adaptation to starvation imposes contrary effects on the plastic and evolutionary responses of populations to subsequent stressors. When first exposed to new stressors, such populations become extinct more often. If they survive the initial exposure to the new stressors, however, they are more likely to undergo evolutionary rescue.
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- "source–sink dynamics). Both processes are often thought to be unrelated to macroevolutionary processes (Silvertown et al., 1999; Bell & Gonzalez, 2011; Saavedra et al., 2011). Given that macroevolutionary and microecological processes appear to be distinct and operate at different scales, we might not expect a high global richness of a given lineage (say hundreds of species within a genus) to result from frequent local co-occurrence of its members (say, on average, with two or three congeneric species), or vice versa. "
ABSTRACT: AimMany biologists explain the global richness of lineages and local co-occurrence of lineage members by distinct processes: speciation/extinction versus ecological interactions. Moreover, allopatric distribution, rarity and local competition limit local co-occurrence of species even within species-rich lineages. However, whether and why the global richness of lineages relates to local co-occurrence of lineage members has not been tested. We study angiosperms, and hypothesize that in globally species-rich genera species frequently encounter congeners locally, reflecting (1) random sampling of species pools into local communities and (2) processes of global species production and local survival such as hybridization, niche filling and a reduced risk of extinction.LocationNetherlands, South Africa, world-wide.Methods Analysing more than 350,000 plots we quantify per species the observed number of co-occurring congeners as well as the null expectation based on random sampling from species pools. From the literature we quantify the global species richness of genera, and abiotic niche positions and breadths, hybrid status and regional species declines.ResultsIn some genera species frequently encounter congeners locally, while in others congeners are rarely encountered. This is independent of the total number of species encountered, and is consistent between the Netherlands and South Africa. ‘High-co-occurrence genera’ are particularly species rich across the globe, consistently so in most families and even after controlling for niche positions, age and regional richness of genera. Species in high-co-occurrence genera tend to occupy niches that are large and close to congeners’ niches. These species are more often hybrids and rarely decline. Relationships explain little variance (< 10%) but are stronger than expected from random sampling of species rich pools.Main conclusionsLocal co-occurrence and global species richness are largely independent, but not entirely so, reflecting random sampling of pools into communities, niche partitioning, hybridization and the reduced risk of regional extinction in high-co-occurrence genera. Increased extinction risk in low-co-occurrence genera implies a proportionately high loss of lineages and their evolutionary heritage from local communities.
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- "These evolutionary responses then simultaneously feedback on the ecological dynamics, rendering both ecology and evolution heavily intertwined. We now begin to understand such eco-evolutionary dynamics in either natural or experimental metapopulations (Bell & Gonzalez 2011). The importance of eco-evolutionary dynamics is most obvious in metapopulations where dispersal determines the genetic composition and demography of different populations (Kokko & Lopez-Sepulcre 2007). "
ABSTRACT: The 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 stressors.