Introgression Through Rare Hybridization: A Genetic Study of a Hybrid Zone Between Red and Sika Deer (Genus Cervus) in Argyll, Scotland

• Published in: Genetics (Austin) 1999-05, Vol.152 (1), p.355-371
• Main Authors: Goodman, Simon J, Barton, Nick H, Swanson, Graeme, Abernethy, Kate, Pemberton, Josephine M
• Format: Article
• Language: English
• Subjects: Alleles; Animals; Cervus elaphus; Cervus nippon; Deer; Deer - genetics; Deoxyribonucleic acid; DNA; DNA, Mitochondrial - metabolism; Genetics; Heterozygote; Hybridization, Genetic; Linkage Disequilibrium; Microsatellite Repeats; Models, Statistical; Scotland; Studies
• ISSN: 0016-6731; 1943-2631; 1943-2631
• DOI: 10.1093/genetics/152.1.355

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 11 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 approximately 9.2% yr-1 from low frequency and disperse at a rate of approximately 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.