The Stabilizing Effect of Intraspecific Genetic Variation on Population Dynamics in Novel and Ancestral Habitats

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. abstract: Recent studies show that intraspecific genetic variation in asexual species may have large effects on community and ecosystem functions, increasing their stability, productivity, and species richness. However, major questions regarding its population-level impact remain empirically unanswered: (a) How does intraspecific genetic diversity affect the ecological characteristics of sexual species, in which recombination can alter the outcome of causal mechanisms such as selection and niche diversification? (b) Does genetic diversity increase population dynamic stability? (c) Is the impact of genetic diversity dependent on the selective environment? To answer these questions, I founded replicate flour beetle (Tribolium castaneum) populations with different degrees of ecologically relevant, heritable trait variation and monitored their dynamics for approximately eight generations. I show that population stability and persistence increased with greater genetic variation but that the stabilizing effect was independent of the selective habitat (different proportions of ancestral and novel resources). Alleles from a single founding strain underwent a selective sweep in the homogeneous ancestral habitat but not in a novel heterogeneous habitat. These results expand current understanding of the ecological impacts of genetic diversity by showing that genetically more diverse sexual populations persist longer and are more stable but that the selective environment determines the mechanistic basis of increased stability.

The probability of evolutionary rescue: towards a quantitative comparison between theory and evolution experiments

“…Bell & Gonzalez [13] showed a clear threshold in population size below which rescue was very unlikely in Saccharomyces cerevisiae undergoing salt stress, as predicted by theory [9]. Ramsayer et al [20] studied adaptation of Pseudomonas fluorescens to antibiotic stress; they found that rescue probability increased with the genetic diversity at the onset of stress [17], giving qualitative support to other facets of evolutionary rescue theory.…”

“…However, these assumptions may also not be so limiting, at least in some natural contexts: (i) when the genetic basis for the rescue is a single gene the system may behave almost as an asexual, (ii) when densities in the stress are low, density-independent growth may be driving the demographic dynamics. All these issues are a matter of experimental testing of course (for an example of rescue experiments with a sexual species, see Agashe and co-workers [16,17]). A second key assumption of our model is that the environment changes abruptly from one where the population thrives to one where it starts to decline, the rate of decline remaining constant thereafter.…”

“…Usually, however, extinction has been considered as a nuisance in experimental evolution. Only recently, several studies have tackled the challenge of describing the probability of evolutionary rescue, using fastreproducing organisms in microcosms with various stresses causing decline, such as yeast adapting to saline conditions [13,14], virus adapting to high temperature [15], flour beetles adapting to a new host [16,17] or bacteria adapting to antibiotic stress [18]. The study of the emergence of resistance to chemotherapy in microbes also has a very long and fruitful history (reviewed in recent studies [3,19]), which relates directly to evolutionary rescue.…”

Intraspecific genetic variation and competition interact to influence niche expansion

“…However, our assumption is supported by various lines of evidence from previous work with the same strain combinations. First, ecologically relevant variation in these combinations was large enough to cause significantly different population dynamics and persistence in a comparable time period in WC habitats (Agashe 2009). Second, under strong directional selection in a corn-only habitat, four-strain combinations showed a significantly faster increase in fecundity on corn (Agashe et al in preparation).…”

Non-random gene flow: an underappreciated force in evolution and ecology

“…For instance, many phytophagous insects exhibit preferences for (or aversions to) the scent of particular host plants (reviewed in [30,31]). Such preferences sometimes coincide with higher performance in the preferred habitat [32] (see also Figure 1) but, in other cases, preference and performance are decoupled (e.g., [33][34][35]). Consequently, we separate the idea of genetic variation in habitat preference, from preference arising pleiotropically from genetic variation in performance in a habitat (source 1, above).…”