Species-specific responses to landscape fragmentation: implications for management strategies.

Simon Blanchet,Olivier Rey,Géraldine Loot,Sovan Lek,Roselyne Etienne

doi:10.1111/j.1752-4571.2009.00110.x

Abstract

Habitat fragmentation affects the integrity of many species, but little is known about species-specific sensitivity to fragmentation. Here, we compared the genetic structure of four freshwater fish species differing in their body size (Leuciscus cephalus; Leuciscus leuciscus; Gobio gobio and Phoxinus phoxinus) between a fragmented and a continuous landscape. We tested if, overall, fragmentation affected the genetic structure of these fish species, and if these species differed in their sensitivity to fragmentation. Fragmentation negatively affected the genetic structure of these species. Indeed, irrespective of the species identity, allelic richness and heterozygosity were lower, and population divergence was higher in the fragmented than in the continuous landscape. This response to fragmentation was highly species-specific, with the smallest fish species (P. phoxinus) being slightly affected by fragmentation. On the contrary, fish species of intermediate body size (L. leuciscus and G. gobio) were highly affected, whereas the largest fish species (L. cephalus) was intermediately affected by fragmentation. We discuss the relative role of dispersal ability and effective population size on the responses to fragmentation we report here. The weirs studied here are of considerable historical importance. We therefore conclude that restoration programmes will need to consider both this societal context and the biological characteristics of the species sharing this ecosystem.

Highlights

Habitat fragmentation is probably the most pervasive effect humans impose on wild species (Vitousek et al 1997; Lawler et al 2006)
We compared the genetic structure of four freshwater fish species differing in their body size (Leuciscus cephalus; Leuciscus leuciscus; Gobio gobio and Phoxinus phoxinus) between a fragmented and a continuous landscape
An important question that needs to be resolved for predicting the ecological and evolutionary damages caused by habitat fragmentation is as follows: is the response to habitat fragmentation species-specific? Answering this question is essential for ecological managers as it allows the identification of ‘umbrella species’ (i.e. species whose environmental requirements encapsulate the needs of a 2010 Blackwell Publishing Ltd 3 (2010) 291–304

Summary

Introduction

Habitat fragmentation is probably the most pervasive effect humans impose on wild species (Vitousek et al 1997; Lawler et al 2006) It is among the most highly studied phenomenon of the process of global change, and many studies have improved our knowledge on the ecological and evolutionary outcomes of fragmented populations (Fahrig 2003; Ewers and Didham 2006; Lawler et al 2006). At the meta-population scale, habitat fragmentation causes habitat patches to be reduced in size and to be isolated from one another, decreasing gene flow between patches (Fahrig 2003) For most species, this spatial rearrangement decreases the effective population size as well as genetic diversity at the patch scale, through the processes of genetic drift and inbreeding (Frankham 1998; Couvet 2002; DiBattista 2008). In the better cases, changes in the genetic structure of connected populations modify their evolutionary trajectory (by changes in life-history characteristics for instance Johansson et al 2007; Waples et al 2008), or in the worst cases, lead to local extinction (Spielman et al 2004).

Methods

Results

Discussion

Conclusion