Effects of genotypic and phenotypic variation on establishment are important for conservation, invasion, and infection biology

Abstract

There is abundant evidence that the probability of successful establishment in novel environments increases with number of individuals in founder groups and with number of repeated introductions. Theory posits that the genotypic and phenotypic variation among individuals should also be important, but few studies have examined whether founder diversity influences establishment independent of propagule pressure, nor whether the effect is model or context dependent. I summarize the results of 18 experimental studies and report on a metaanalysis that provides strong evidence that higher levels of genotypic and phenotypic diversity in founder groups increase establishment success in plants and animals. The effect of diversity is stronger in experiments carried out under natural conditions in the wild than under seminatural or standardized laboratory conditions. The realization that genetic and phenotypic variation is key to successful establishment may improve the outcome of reintroduction and translocation programs used to vitalize or restore declining and extinct populations. Founder diversity may also improve the ability of invasive species to establish and subsequently spread in environments outside of their native community, and enhance the ability of pathogens and parasites to colonize and invade the environment constituted by their hosts. It is argued that exchange of ideas, methodological approaches, and insights of the role of diversity for establishment in different contexts may further our knowledge, vitalize future research, and improve management plans in different disciplines.

Keywords: biodiversity; biological invasion; colonization; extinction.

Fig. 1.

Comparison of effect sizes in experiments testing whether genotypic and phenotypic diversity promotes establishment success. Mean (±SD) effect size measured as Cohen’s d in plants and animals, and for experiments performed in the laboratory, under seminatural conditions or under field conditions in the wild. The numbers above the horizontal axis indicate sample sizes. The figure shows raw data, but the statistical analyses were based on log(x + 1)-transformed data.

Fig. 2.

Funnel plot to assess publication bias in experimental tests for effects of founder diversity on establishment success. The figure shows the relationship between study size, measured as number of replicates, and effect size measured as Cohen’s d. Publication bias might be suspected if small studies (with few replicates) reporting low effect sizes are absent but small studies reporting high effect sizes are present. Effect size was not significantly related to study size [regression of effect size on log number of replicates; F_(1,16) = 1.63, P = 0.22, R² = 0.09].