Human-aided dispersal has altered but not erased the phylogeography of the tench.

Otomar Linhart,Petr Kotlík,Zdeněk Lajbner

doi:10.1111/j.1752-4571.2010.00174.x

Abstract

Human-aided dispersal can result in phylogeographic patterns that do not reflect natural historical processes, particularly in species prone to intentional translocations by humans. Here, we use a multiple-gene sequencing approach to assess the effects of human-aided dispersal on phylogeography of the tench Tinca tinca, a widespread Eurasian freshwater fish with a long history in aquaculture. Spatial genetic analysis applied to sequence data from four unlinked loci and 67 geographic localities (38–382 gene copies per locus) defined two groups of populations that were little structured geographically but were significantly differentiated from each other, and it identified locations of major genetic breaks, which were concordant across genes and were driven by distributions of two phylogroups. This pattern most reasonably reflects isolation in two major glacial refugia and subsequent range expansions, with the Eastern and Western phylogroups remaining largely allopatric throughout the tench range. However, this phylogeographic variation was also present in all 17 cultured breeds studied, and some populations at the western edge of the native range contained the Eastern phylogroup. Thus, natural processes have played an important role in structuring tench populations, but human-aided dispersal has also contributed significantly, with the admixed genetic composition of cultured breeds most likely contributing to the introgression.

Highlights

Determining the effects of human-aided dispersal and how it overlays with natural distributional changes is essential for the effective protection of species throughout their native ranges
We focused on the female component of population, which is represented in our data by mtDNA variation, because of its relatively shallower coalescence time depth and shorter expected the most recent common ancestor (TMRCA) compared with autosomal loci
The difficulty of disentangling the confounding effects of secondary dispersal from the impact of natural historical processes presents a persistent challenge for studies on the historical biogeography, of species prone to intentional translocation by humans

Summary

Introduction

Determining the effects of human-aided dispersal and how it overlays with natural distributional changes is essential for the effective protection of species throughout their native ranges. Translocations that occur within the limits of the natural distribution of a species do not extend its range but instead superimpose new genetic signatures on the natural diversity patterns if they involve genetically divergent populations or domestic breeds (Taylor 2004; Ferguson et al 2007; Stone et al 2007; Mabuchi et al 2008; Randi 2008; Muhlfeld et al 2009). The impacts of such translocations are more difficult to detect. Few economically important species have been studied phylogeographically across their ranges, but even in those cases, the focus has been primarily on putative native populations, assuming (or hoping for) negligible phylogeographic contribution of human-aided a 2011 Blackwell Publishing Ltd 4 (2011) 545–561

Results

Discussion

Conclusion