Contrasting effects of long distance seed dispersal on genetic diversity during range expansion

Abstract

Currently many attempts are made to reconstruct the colonization history of plant species after the last ice age. A surprising finding is that during the colonization phase genetic diversity did not decrease as much as expected. In this paper we examine whether long distance seed dispersal events could play a role in the unexpected maintenance of genetic diversity during range expansion. This study is based on simulations carried out with a maternally inherited haploid locus using a cellular automaton. The simulations reveal a close relationship between the frequency of long distance seed dispersal events and the amount of genetic diversity preserved during colonization. In particular, when the colonized region is narrow, a complete loss of genetic diversity results from the occurrence of very rare long distance dispersal (LDD) events. We call this phenomenon the ‘embolism effect’. However, slightly higher rates of LDD events reverse this effect, up to the point that diversity is better preserved than in a pure diffusion model. This phenomenon is linked to the reorganization of the genetic structure during colonization and is called the ‘reshuffling effect’.

Evidence of rapid change in genetic structure and diversity during range expansion in a recovering large terrestrial carnivore

“…By contrast, we found a clear correlation between the increase in the number of migrants and population growth. As previously mentioned, the latter may decrease founder effects [10] and only slightly higher rates of long distance dispersal events preserve genetic diversity by reshuffling alleles across the landscape [19,62]. Population growth alone should give an excess of rare alleles, an excess of homozygosity and little linkage disequilibrium [5], but none of these three characteristics were observed in our study.…”

How connectivity shapes genetic structure during range expansion: Insights from the Virginia's Warbler

“…Range expansion with recurring gene flow could curtail the loss of neutral and functional genetic diversity in newly colonized areas. In this case, genetic diversity is maintained in peripheral populations through immigration and multiple introduction events (Bialozyt et al 2005). Alternatively, range expansion across uninhabitable regions to habitat islands could produce founder events, and without recurring gene flow could substantially decrease genetic variation in newly colonized areas.…”

Serial founder effects and genetic differentiation during worldwide range expansion of monarch butterflies

“…While these studies demonstrated the effects of genetic drift in shaping population genetics associated with range expansions, few studies have been carried out on organisms that undertake frequent and long-distance migrations. Simulations predicted that while serial founder events can cause genetic diversity loss and greater differentiation, these effects can be reduced by high dispersal [20][21][22]. Indeed, the disappearance or reduction of an isolation-by-distance pattern has been shown in a handful of species capable of long-range dispersal [23,24].…”