A rapid, strong, and convergent genetic response to urban habitat fragmentation in four divergent and widespread vertebrates.

Kathleen Semple Delaney,Robert N Fisher,Seth P D Riley,Robert C Fleischer

doi:10.1371/journal.pone.0012767

Kathleen Semple Delaney, Robert N Fisher + Show 2 more

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https://doi.org/10.1371/journal.pone.0012767

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Abstract

BackgroundUrbanization is a major cause of habitat fragmentation worldwide. Ecological and conservation theory predicts many potential impacts of habitat fragmentation on natural populations, including genetic impacts. Habitat fragmentation by urbanization causes populations of animals and plants to be isolated in patches of suitable habitat that are surrounded by non-native vegetation or severely altered vegetation, asphalt, concrete, and human structures. This can lead to genetic divergence between patches and in turn to decreased genetic diversity within patches through genetic drift and inbreeding.Methodology/Principal FindingsWe examined population genetic patterns using microsatellites in four common vertebrate species, three lizards and one bird, in highly fragmented urban southern California. Despite significant phylogenetic, ecological, and mobility differences between these species, all four showed similar and significant reductions in gene flow over relatively short geographic and temporal scales. For all four species, the greatest genetic divergence was found where development was oldest and most intensive. All four animals also showed significant reduction in gene flow associated with intervening roads and freeways, the degree of patch isolation, and the time since isolation.Conclusions/SignificanceDespite wide acceptance of the idea in principle, evidence of significant population genetic changes associated with fragmentation at small spatial and temporal scales has been rare, even in smaller terrestrial vertebrates, and especially for birds. Given the striking pattern of similar and rapid effects across four common and widespread species, including a volant bird, intense urbanization may represent the most severe form of fragmentation, with minimal effective movement through the urban matrix.

Highlights

Habitat loss and the resulting fragmentation can have many impacts on wildlife populations
We found no significant correlations between genetic distance (FST) and geographic distance in any of the four species, suggesting no pattern of isolation by distance (Table 2)
Loss of genetic connectivity Using three different methods, traditional pair-wise genetic distance analysis (FST; Table S1), landscape genetic analysis (Fig. 1b), and Bayesian genetic clustering (Fig. 2), we found significant genetic differences between sample locations in all four species

Summary

Introduction

Habitat loss and the resulting fragmentation can have many impacts on wildlife populations. For species that remain widely distributed across fragmented landscapes, connectivity and gene flow between populations may be reduced, leading to longer-term problems such as inbreeding, loss of genetic diversity, and even local extinction [4,5,6,7]. Habitat fragmentation by urbanization causes populations of animals and plants to be isolated in patches of suitable habitat that are surrounded by non-native vegetation or severely altered vegetation, asphalt, concrete, and human structures. This can lead to genetic divergence between patches and in turn to decreased genetic diversity within patches through genetic drift and inbreeding

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