The genetic consequences of long distance dispersal during colonization

Abstract

Rare long distance dispersal may have little impact on gene frequencies in established populations but it can dramatically increase gene flow during episodes of range expansion. We model the invasion of new territory by genetically distinct populations of the same species to investigate the dynamics of such episodes. If long distance dispersal is sufficiently frequent, the populations do not spread as a wave of advance but instead found intermingled isolates. We argue that this process can explain many otherwise puzzling patterns in the geographical distribution of alleles.

Complex postglacial history of the temperate bark beetle Tomicus piniperda L. (Coleoptera, Scolytinae)

“…This pattern can be explained if this group of haplotypes survived in a glacial refugium located in the north of the Iberian Peninsula and reached Northern Europe during an interglacial, as is suggested by the occurrence of haplotype 1I up to Estonia and Russia, in long distance movements similar to that of Iberian haplotypes 2A and 2G (Nichols and Hewitt, 1994). During the following glacial episode, some individuals may have been trapped in Italy and the Balkans, whereas some were still present in the Pyrenees.…”

Phylogeographic history of the yellow-necked fieldmouse (Apodemus flavicollis) in Europe and in the Near and Middle East

“…Within the European lineage, as predicted by the expansion/contraction model (Nichols and Hewitt, 1994;Santucci et al, 1998), the analysis of nucleotide diversity (Table 2) suggests that the Italo-Balkan region was a refuge for A. flavicollis. Indeed, these populations are characterised by genetic diversity significantly higher (p ¼ 0:015, p < 0:05) than in northern, eastern or western populations.…”

Early insights into the genetic consequences of range expansions

“…Although metapopulation models can be seen as representing a first step in this direction, they deal with local colonization balanced by extinctions, not pure expansions (Slatkin, 1977). The first quantitative studies of the genetic consequences of colonization of a new territory were published some 15-25 years ago and relied initially on simulations (Rendine et al, 1986;Nichols and Hewitt, 1994;Ibrahim et al, 1996), with analytical approaches following shortly after (Austerlitz et al, 1997;reviewed by Excoffier et al, 2009). Below, we consider one of these papers, published 14 years ago in Heredity (Ibrahim et al, 1996), which turned out to be particularly influential, with over 300 citations reported to date in ISI Web of Science, most of them after 2001.…”

“…Another work published 2 years earlier by the same group (Nichols and Hewitt, 1994) had prepared the way for the paper by Ibrahim et al However, the study, which had been stimulated by surveys revealing genetic mixing between races of a grasshopper in the Pyrenees, was dealing with a more specific question (the admixture between genetically differentiated populations) and did not attract as much attention.…”

“…Spatially explicit studies entirely dedicated to the genetic consequences of short-distance dispersal (Edmonds et al, 2004;Klopfstein et al, 2006) appeared much later than those focusing on the genetic consequences of long-distance dispersal (Nichols and Hewitt, 1994;Ibrahim et al, 1996). They led to the characterization of the 'surfing' phenomenon, that is, the possibility for rare variants to rapidly increase in frequency as a consequence of strong genetic drift occurring in populations located on the edge of the expansion (Excoffier and Ray, 2008).…”