Genetic Population Structure and Allele Surfing During Range Expansion in Dynamic Habitats.

Rosana T Braga,José A.F Diniz-Filho,Thiago F Rangel,João F.M Rodrigues

doi:10.1590/0001-3765201920180179

Rosana T Braga, José A.F Diniz-Filho + Show 2 more

Open Access

https://doi.org/10.1590/0001-3765201920180179

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Abstract

Expanding populations may loss genetic diversity because sequential founder events throughout a wave of demographic expansion may cause "allele surfing", as the alleles of founder individuals may propagate rapidly through space. The spatial components of allele surfing have been studied by geneticists, but have never been investigate on dynamic and shifting habitats. Here we used an individual-based-model (IBM) to study how interactions between different habitat restoration scenarios and biological characteristics (dispersal capacity) affect the spatial patterns of the genetic structure of a population during demographic expansion. We found that both habitat dynamics and dispersal capacity, as well as their interaction, were the drivers of emergent pattern of genetic diversity and allele surfing. Specifically, allele surfing is more common when a species with low dispersal capacity colonizes a large geographic area with slow restoration (low carrying capacity). Despite this, we showed that allele surfing can be reduced, or even avoided, by dispersal management through suitable habitat restoration. Thus, investigating how colonization generates a spatial variation in genetic diversity, and which parameters control the emergent genetic pattern, are essential steps to planning assisted gene flow, which is fundamental for an effective planning of habitat restoration.

Highlights

Population expansions commonly occur during the evolutionary history of many species, and are expected to be followed by retraction and subsequent population re-expansion (Ricklefs and Bermingham 2002)
The highest Z-values were observed at low dispersal capacity, allele surfing occurred regardless of dispersal capacity in this scenario, indicating that when habitat restoration occurs slowly along the whole surrounding area, demographic expansion decreases genetic variability of populations with any dispersal capacity along the expansion
For species with high dispersal capacity, the spatial structure and rate of habitat restoration seem irrelevant to the occurrence of allele surfing

Summary

Introduction

Population expansions commonly occur during the evolutionary history of many species, and are expected to be followed by retraction and subsequent population re-expansion (Ricklefs and Bermingham 2002). Anthropogenic habitat destruction and fast climatic changes have increased the speed and intensity in which populations expand or retract (Amos et al 2012), with unexpected ecological and evolutionary consequences, such as a decrease of genetic variability, which would occur naturally over much larger temporal scales During rapid demographic expansions, the expanding population may have substantially less genetic diversity due to a founder effect, wherein, the genetic pool of newly occupied habitats originates from a small sample of pioneer individuals (Hallatschek and Nelson 2008, Slatkin and Excoffier 2012). Spatial models show that rapid population expansion may generate a pattern of decreasing genetic variability with the increase in geographic distance from the source population (Excoffier and Ray 2008, Hallatschek and Nelson 2009)

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