Geographic variation and genetic structure in Spotted Owls

We examined genetic variation, populationstructure, and definition of conservation unitsin Spotted Owls (Strix occidentalis). Spotted Owls are mostly non-migratory,long-lived, socially monogamous birds that havedecreased population viability due to theiroccupation of highly-fragmented latesuccessional forests in western North America. To investigate potential effects of habitatfragmentation on population structure, we usedrandom amplified polymorphic DNA (RAPD) toexamine genetic variation hierarchicallyamong local breeding areas, subregionalgroups, regional groups, and subspeciesvia sampling of 21 breeding areas (276individuals) among the three subspecies ofSpotted Owls. Data from 11 variable bandssuggest a significant relationship betweengeographic distance among local breeding groupsand genetic distance (Mantel r = 0.53, P< 0.02) although multi-dimensional scaling ofthree significant axes did not identifysignificant grouping at any hierarchical level. Similarly, neighbor-joining clustering ofManhattan distances indicated geographicstructure at all levels and identified MexicanSpotted Owls as a distinct clade. RAPDanalyses did not clearly differentiate NorthernSpotted Owls from California Spotted Owls. Among Northern Spotted Owls, estimates ofpopulation differentiation (F_ST) rangedfrom 0.27 among breeding areas to 0.11 amongregions. Concordantly, within-group agreementvalues estimated via multi-response permutationprocedures of Jaccard's distances ranged from0.22 among local sites to 0.11 among regions. Pairwise comparisons of F_ST andgeographic distance within regions suggestedonly the Klamath region was in equilibrium withrespect to gene flow and genetic drift. Merging nuclear data with recent mitochondrialdata provides support for designation of anEvolutionary Significant Unit for MexicanSpotted Owls and two overlapping ManagementUnits for Northern and California Spotted Owls.