Introgression through rare hybridization: A genetic study of a hybrid zone between red and sika deer (genus Cervus) in Argyll, Scotland

S J Goodman, N H Barton, G Swanson, K Abernethy, J M Pemberton

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Abstract

In this article we describe the structure of a hybrid zone in Argyll, Scotland, between native red deer ( Cervus elaphus) and introduced Japanese sika deer ( Cervus nippon), on the basis of a genetic analysis using II microsatellite markers and mitochondrial DNA. In contrast to the findings of a previous study of the same population, we conclude that the deer fall into two distinct genetic classes, corresponding to either a sika-like or red-like phenotype. Introgression is rare at any one locus, but where the taxa overlap up to 40% of deer carry apparently introgressed alleles. While most putative hybrids are heterozygous at only one locus, there are rare multiple heterozygotes, reflecting significant linkage disequilibrium within both sika- and red-like populations. The rate of backcrossing into the sika population is estimated as H = 0.002 per generation and into red, H = 0.001 per generation. On the basis of historical evidence that red deer entered Kintyre only recently, a diffusion model evaluated by maximum likelihood shows that sika have increased at similar to 9.2% yr(-1) from low frequency and disperse at a rate of similar to 3.7 km yr(-1). Introgression into the red-like population is greater in the south, while introgression into sika varies little along the transect. For both sika- and red-like populations, the degree of introgression is 30-40% of that predicted from the rates of current hybridization inferred from linkage disequilibria; however, in neither case is this statistically significant evidence for selection against introgression.

Original languageEnglish
Pages (from-to)355-371
Number of pages17
JournalGenetics
Volume152
Issue number1
Publication statusPublished - May 1999

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