Colonization with long-distance seed dispersal and genetic structure of maternally inherited genes in forest trees: a simulation study

Abstract

Since the last glacial period forest trees have expanded to their present range very rapidly, with rates up to 500 m yr−1 for oaks in Europe, which can be explained only by the dispersion of acorns over long distances. We used a stratified dispersal model, including both diffusive and long-distance dispersal of seeds, to simulate the colonization of a 100 km×300 km grid by populations of oak trees. An appropriate rate of spread is obtained with rare dispersal at distances of the order of tens of kilometres. We simulated the effect of stratified versus diffusive dispersal of seeds on the spatial genetic structure at a maternally inherited locus. Founding events associated with stratified dispersal generate a high amount of genetic differentiation among populations, which is likely to persist for a long time after colonization. Using autocorrelation methods, we show that diffusive and stratified dispersals create quite different spatial patterns of variation for the maternally inherited locus. Stratified dispersal creates patchy patterns that are concordant with a previous experimental investigation of chloroplast DNA variation at a regional scale in the oaks Quercus petraea and Quercus robur. For plant populations that have passed through recent episodes of range expansion, long-distance dispersal events are probably the most important factors of spatial genetic structuring of maternally inherited genes at small or medium geographic scales.

A Spatially Explicit Neutral Model of β-Diversity in Tropical Forests

“…Relating the gene flow between different locales to the distance between these locales is a great challenge. Le Corre et al (1997) have explored the influence of longdistance gene flow on the genetic structure of a tree population. Our analytical model could prove a useful null hypothesis for such investigations.…”

An investigation into effects of long-distance seed dispersal on organelle population genetic structure and colonization rate: a model analysis

“…Even with the recent increase in molecular studies targeting maternally inherited, and therefore seed-dispersed, genomes (eg chloroplast DNA (cpDNA) in Angiosperms), sample sizes are usually too small to reveal detailed information on the dynamics of these potentially very rare events. However, the importance of rare long-distance dispersal events to the colonizing ability of a species has been highlighted by a number of studies and has been influential in determining colonization patterns following glacial periods (Skellam, 1951;Hewitt, 1996;Ibrahim et al, 1996;Le Corre et al, 1997;Cain et al, 1998Cain et al, , 2000Clark, 1998;Clark et al, 1999;Petit et al, 2000). For forest trees, the timings and direction of postglacial colonization have been investigated using analysis of fossil pollen data and simulation studies (eg Birks, 1989;Hewitt, 1996Hewitt, , 1999Le Corre et al, 1997).…”

“…These studies indicate that expansion from refugial centres following glacial retreat is often rapid and so must have involved long-distance dispersal events that set up colonies well ahead of the main species advance. The maternally inherited genome of such colonists can then come to dominate leading populations, since later migrants will need to invade established populations at carrying capacity (Hewitt, 1993;Ibrahim et al, 1996;Le Corre et al, 1997).…”

Early insights into the genetic consequences of range expansions

“…Retrospectively, it is curious to realize that, in the study by Ibrahim et al and in related studies (such as that by Le Corre et al, 1997), simulations of the genetic consequences of simple diffusion are used only as a baseline for comparisons Heredity (2011Heredity ( ) 106, 203-204 & 2011 Macmillan Publishers Limited All rights reserved 0018-067X/11 www.nature.com/hdy with models including long-distance dispersal, considered to be biologically more relevant. 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).…”