Differences between the costs and establishment rates of clonal and sexual offspring affect the probability of evolutionary rescue in plant populations

Evolutionary rescue can facilitate population persistence following an environmental change, but the success of this process depends on a large number of factors. To date, only a small number of theoretical studies have considered the impact of reproductive mode, specifically facultative sex, on evolutionary rescue despite the prevalence of organisms that implement this reproductive strategy. These initial studies concluded that greater investment in clonal reproduction generally increases the probability of evolutionary rescue following an abrupt environmental change and reduces the probability of rescue following a directional environmental change. However, one key assumption of the underlying models is that clonal offspring are equivalent to sexual offspring with respect to production costs and juvenile survivorship. Previous work instead suggests that clonal offspring tend to be more costly to produce and have higher juvenile survivorship compared to sexual offspring; the contribution of sexual offspring to the maintenance of established populations is also known to be highly variable across clonal plant species. This study evaluated how these differences between clonal and sexual offspring impact the relationship between clonal allocation and the probability of evolutionary rescue by increasing the relative cost of clonal offspring and varying the relative establishment rate of sexual offspring in simulated clonal plant populations. Following an abrupt environmental change, greater clonal reproduction increased the probability of evolutionary rescue only when the establishment rate of sexual offspring was low. The sexual establishment rate did not affect the outcome following a directional environmental change: greater clonal reproduction always reduced the probability of evolutionary rescue. Across all simulations, the probability of evolutionary rescue fell as the establishment rate of sexual offspring declined. Incorporating known differences between clonal and sexual offspring into models of clonal plant populations is thus critical for understanding the persistence of natural populations in the face of environment change.