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Country‐wide genetic monitoring over 21 years reveals lag in genetic recovery despite spatial connectivity in an expanding carnivore (Eurasian otter, Lutra lutra) population

Citation

Thomas, Nia E.; Hailer, Frank; Bruford, Michael W.; Chadwick, Elizabeth A. (2022), Country‐wide genetic monitoring over 21 years reveals lag in genetic recovery despite spatial connectivity in an expanding carnivore (Eurasian otter, Lutra lutra) population, Dryad, Dataset, https://doi.org/10.5061/dryad.v6wwpzh0h

Abstract

Numerous terrestrial mammal species have experienced extensive population declines during past centuries, due largely to anthropogenic pressures. For some species, including the Eurasian otter (Lutra lutra), environmental and legal protection has more recently led to population growth and recolonisation of parts of their historic ranges. While heralded as conservation successes, only a few such recoveries have been examined from a genetic perspective, i.e. whether genetic variability and connectivity have been restored. We here use large-scale and long-term genetic monitoring data from UK otters, whose population underwent a well-documented population decline between the 1950s to 1970s, to explore the dynamics of a population re-expansion over a 21-year period. We genotyped otters from across Wales and England at five time points between 1994 and 2014 using 15 microsatellite loci. We used this combination of long-term temporal and large-scale spatial sampling to evaluate 3 hypotheses relating to genetic recovery; that (i) gene flow between sub-populations would increase over time, (ii) genetic diversity of previously isolated populations would increase, and that (iii) genetic structuring would weaken over time. Although we found an increase in inter-regional gene flow and admixture levels among subpopulations, there was no significant temporal change in either heterozygosity or allelic richness. Genetic structuring among the main sub-populations hence remained strong and showed a clear historical continuity. These findings highlight an underappreciated aspect of population recovery of endangered species, that genetic recovery may often lag behind the processes of spatial and demographic recovery. In other words, the restoration of physical connectivity of populations does not necessarily lead to genetic connectivity. Our findings emphasise the need for genetic data as an integral part of conservation monitoring, to enable the potential vulnerability of populations to be evaluated.

Methods

DNA extracted from muscle tissue samples, PCR of microsatellite loci, fragment analysis with fluorescent labels on capillary instrument, manual genotype calling.

Usage Notes

Text editor or spreadsheet software such as Excel.

Funding

Natural Environment Research Council, Award: NE/L002434/1

British Ecological Society, Award: SEPG 1133/1404