The impact of river fragmentation on the population persistence of native and alien mink: an ecological trap for the endangered European mink

Andrzej Zalewski,Jabi Zabala,Hanna Zalewska,Iñigo Zuberogoitia

doi:10.1007/s10531-012-0410-3

Andrzej Zalewski, Jabi Zabala + Show 2 more

Open Access

https://doi.org/10.1007/s10531-012-0410-3

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Abstract

The genetic diversity of feral and ranch American mink was studied in order to detect gene flux among rivers, investigate the processes of invasion, and determine the possible effects of river barriers. Tissue samples of 78 feral American mink from 5 different river catchments and 18 ranch mink, collected between 2007 and 2011 in Biscay, northern Spain, were genotyped at 21 microsatellite loci. Lack of genetic differentiation of feral mink among the sites and high differentiation between feral and ranch mink was suggested. These results confirm that the mink population established on Butron River at the beginning of the 1990s may be the origin of almost all the feral mink population within the study area. Additionally, the occurrence of American and European mink was used to analyse the effect of fragmentation on the population viability. The size and composition of the home range of male European mink was considered to model minimum viable units for presence/absence. Forty-two minimum viable units were randomly distributed among rivers in order to analyse the effect of fragmentation on mink occurrence. Barriers were mapped and classified as slight, moderate or absolute, depending on the effect on mink movement, and were introduced into the models. The presence of European and American mink depended on the non-fragmented main river stretches and the number of tributaries free from barriers. Results showed that fragmented rivers can be temporarily occupied but the likelihood of death means that these areas are only sink patches for mink.

Highlights

Habitat loss and degradation are the greatest extinction threats to biodiversity in a variety of ecosystems and taxonomic groups (Jager et al 2006; Fischer and Lindenmayer 2007)
Lack of genetic differentiation of feral mink among the sites and high differentiation between feral and ranch mink was suggested. These results confirm that the mink population established on Butron River at the beginning of the 1990s may be the origin of almost all the feral mink population within the study area
Significant signs of null alleles were found in one loci (Mvi1302) since null alleles may lead to misinterpretation of the data and incorrect biological conclusions, we excluded this loci from further analysis

Summary

Introduction

Habitat loss and degradation are the greatest extinction threats to biodiversity in a variety of ecosystems and taxonomic groups (Jager et al 2006; Fischer and Lindenmayer 2007). Fragmentation makes the difference between persistence and extinction, since longer dispersal distances to find territories increases movement-related mortality, territories include lower quality habitat, which elevated habitat-related mortality and Alee effects (failure to find mates) reduce births (Jager et al 2006). Habitat isolation can have a negative effect on the dispersal of juveniles (by decreasing population connectivity) and, and to an even greater extent, on the day-to-day movements of a given territorial species (Fahrig 2003; Fischer and Lindenmayer 2007; Zabala et al 2007b; Zalewski et al 2009). It is expected that a fragmented habitat can be temporarily occupied by a dispersing individual but the survival likelihood is negatively correlated with the time period spent in the area (see Fischer and Lindenmayer 2007)

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