title: Hybrid swarm between divergent lineages of mule deer (Odocoileus hemionus).
abstract: Studies of hybrid zones have revealed an array of evolutionary outcomes, yet the underlying structure is typically characterized as one of three types: a hybrid zone, a hybrid swarm or a hybrid taxon. Our primary objective was to determine which of these three structures best characterizes a zone of hybridization between two divergent lineages of mule deer (Odocoileus hemionus), mule deer and black-tailed deer. These lineages are morphologically, ecologically and genetically distinct, yet hybridize readily along a zone of secondary contact between the east and west slopes of the Cascade Mountains (Washington and Oregon, USA). Using microsatellite and mitochondrial DNA, we found clear evidence for extensive hybridization and introgression between lineages, with varying degrees of admixture across the zone of contact. The pattern of hybridization in this region closely resembles a hybrid swarm; based on data from 10 microsatellite loci, we detected hybrids that extend well beyond the F1 generation, did not detect linkage disequilibrium at the centre of the zone and found that genotypes were associated randomly within the zone of contact. Introgression was characterized as bidirectional and symmetric, which is surprising given that the zone of contact occurs along a sharp ecotone and that lineages are characterized by large differences in body size (a key component of mating success). Regardless of the underlying mechanisms promoting hybrid swarm maintenance, it is clear that the persistence of a hybrid swarm presents unique challenges for management in this region.
authors: Behavioral and Molecular Ecology Research Group, Department of Biological Sciences, University of Wisconsin-Milwaukee, 3209 N Maryland Ave, Milwaukee, WI 53211, USA. latch@uwm.edu
authors: Emily K
authors: EK
authors: Latch
authors: Elizabeth M
authors: EM
authors: Kierepka
authors: James R
authors: JR
authors: Heffelfinger
authors: Olin E
authors: OE
authors: Rhodes
mesh_terms: D000818:Animals; D005075:Biological Evolution; D016000:Cluster Analysis; D004272:DNA, Mitochondrial / Q000235:genetics / Q000302:isolation & purification; D003670:Deer / Q000145:classification* / Q000235:genetics*; D004463:Ecology; D005260:Female; D056426:Genetic Loci; D014644:Genetic Variation; D005838:Genotype; D006824:Hybridization, Genetic; D008297:Male; D018895:Microsatellite Repeats; D008969:Molecular Sequence Data; D009922:Oregon; D058974:Phylogeography; D017422:Sequence Analysis, DNA; D013045:Species Specificity; D014861:Washington
chemical_list: D004272:DNA, Mitochondrial