Increased genetic divergence between two closely related fir species in areas of range overlap.

Jing Wang,Pär K Ingvarsson,Richard J Abbott,Jianquan Liu

doi:10.1002/ece3.1007

Jing Wang, Pär K Ingvarsson + Show 2 more

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https://doi.org/10.1002/ece3.1007

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Abstract

Because of introgressive hybridization, closely related species can be more similar to each other in areas of range overlap (parapatry or sympatry) than in areas where they are geographically isolated from each other (allopatry). Here, we report the reverse situation based on nuclear genetic divergence between two fir species, Abies chensiensis and Abies fargesii, in China, at sites where they are parapatric relative to where they are allopatric. We examined genetic divergence across 126 amplified fragment length polymorphism (AFLP) markers in a set of 172 individuals sampled from both allopatric and parapatric populations of the two species. Our analyses demonstrated that AFLP divergence was much greater between the species when comparisons were made between parapatric populations than between allopatric populations. We suggest that selection in parapatry may have largely contributed to this increased divergence.

Highlights

Introgression commonly occurs between closely related species in areas where their distributions overlap (Anderson and Hubricht 1938; Rieseberg and Wendel 1993; Sullivan et al 2004; Mehner et al 2010)
The goals of this study were (1) to determine whether there is increased or reduced genetic differentiation between parapatric populations compared with allopatric populations of these two recently diverged fir species; (2) to explore how genetic differentiation is distributed throughout the genome and whether regions of divergence are concentrated in just a few ‘genomic islands’ or is widespread across the genome
In contrast to an initial expectation that genetic divergence between parapatric populations of two species of Abies, A. chensiensis and A. fargesii might be reduced due to introgression, we found that divergence based on amplified fragment length polymorphism was much greater between parapatric populations than between allopatric populations

Summary

Introduction

Introgression commonly occurs between closely related species in areas where their distributions overlap (Anderson and Hubricht 1938; Rieseberg and Wendel 1993; Sullivan et al 2004; Mehner et al 2010). A distinct pattern of increased interspecific differentiation between closely related species in parapatry (or sympatry) compared with that in allopatry has been reported for ecological and reproductive traits in a number of animals and plants (Levin 1978; Sætre et al 1997; Grant and Grant 2006; Niet et al 2006; Kay and Schemske 2008; Smith and Rausher 2008; Urbanelli and Porretta 2008; Kirschel et al 2009; Grossenbacher and Whittall 2011) This process of divergence of characters between species in response to selection is usually termed “character displacement” (Brown and Wilson 1956; Pfennig and Pfennig 2009).

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