Bidirectional introgressive hybridization between Lepus capensis and Lepus yarkandensis

Lepus capensis and Lepus yarkandensis are two well-established hare species with different habitat preferences and obvious morphological distinctions. L. capensis is common and widespread while L yarkandensis is an endemic species with a restricted distribution in the Tarim Basin of western China. During field sampling, individuals with a distinct phenotype were found in the contact zone between the two species. To understand the origin of these unclassified individuals, we analyzed morphological and genetic data from 700 individuals including L yarkandensis, L. capensis and the unclassified individuals. Morphological analyses of the unclassified individuals revealed that they lie between L. yarkandensis and L capensis. Genetic analyses based on species-specific molecular markers (mitochondrial control region and SRY) showed that the unclassified populations have mtDNA and SRY genes from both L capensis and L. yarkandensis, suggesting that the unclassified populations result from hybridization between the two species. Interestingly, many identical and/or very similar mtDNA haplotypes were shared between L capensis populations and L yarkandensis populations close to their contact zones, which further suggests the existence of extensive bidirectional mtDNA introgression. Similarly, we found evidence for SRY introgression, though it existed at a lower level compared to mtDNA introgression. (C) 2011 Elsevier Inc. All rights reserved.