GENETIC-DIFFERENCES BETWEEN THE ENDANGERED SAN-CLEMENTE ISLAND LOGGERHEAD SHRIKE LANIUS LUDOVICIANUS-MEARNSI AND 2 NEIGHBORING SUBSPECIES DEMONSTRATED BY MTDNA CONTROL REGION AND CYTOCHROME-B SEQUENCE VARIATION

We investigated mtDNA sequence variation in five populations of the lo ggerhead shrike Lanius ludovicianus, representing four subspecies, inc luding the San Clemente loggerhead shrike L. l. mearnsi, a critically endangered California Channel Island endemic. Variability in 200 bp of control region and 200 bp of cytochrome b was extremely low, and defi ned four haplotypes. Strong structure was apparent among all three sou thern Californian subspecies, including L. l. mearnsi, with one haplot ype predominating in each subspecies. Although potential levels of gen e flow between L. l. mearnsi and neighbouring populations are low, mtD NA data support field observations that some shrikes visit the island during winter but do not stay to breed, and suggest that these birds c ome from the mainland. The similarity In haplotypes between population s from Saskatchewan, Canada and those in southern California suggests post-glacial northern range expansion of the species. Our results conf irm the evolutionary distinctiveness of L. l. mearnsi and justify cont inuing efforts for its conservation.