Gene flow between insular, coastal and interior populations of brown bears in Alaska

Abstract

The brown bears of coastal Alaska have been recently regarded as comprising from one to three distinct genetic groups. We sampled brown bears from each of the regions for which hypotheses of genetic uniqueness have been made, including the bears of the Kodiak Archipelago and the bears of Admiralty, Baranof and Chichagof (ABC) Islands in southeast Alaska. These samples were analysed with a suite of nuclear microsatellite markers. The 'big brown bears' of coastal Alaska were found to be part of the continuous continental distribution of brown bears, and not genetically isolated from the physically smaller 'grizzly bears' of the interior. By contrast, Kodiak brown bears appear to have experienced little or no genetic exchange with continental populations in recent generations. The bears of the ABC Islands, which have previously been shown to undergo little or no female-mediated gene flow with mainland populations, were found not to be genetically isolated from mainland bears. The data from the four insular populations indicate that female and male dispersal can be reduced or eliminated by water barriers of 2-4 km and 7 km in width, respectively.

Population genetics of Ice Age brown bears

“…Furthermore, the precise correspondence between geographic and phylogenetic divisions suggests three evolutionary significant units for conservation (9, 13) (clades II, III, and IV). In contrast, nuclear microsatellite data in Alaskan brown bears do not support long-term genetic isolation of the three Alaskan clades, suggesting the possibility of sex-biased dispersal (14).…”

Using a reference population yardstick to calibrate and compare genetic diversity reported in different studies: an example from the brown bear

“…This latter population is relatively large (42500) and healthy, with low genetic diversity attributed to a long period of isolation from the bears on the continent (Paetkau et al, 1998a(Paetkau et al, , 1998b. On the other hand, the demographic history of the other populations with low genetic diversity is presumed to be one of a recent contraction and isolation.…”

Combined use of maternal, paternal and bi-parental genetic markers for the identification of wolf–dog hybrids

“…To study the likelihood of finding one of the observed autosomal genotypes in each one of the reference populations, we used an assignment test (Paetkau et al, 1995(Paetkau et al, , 1998Waser and Strobeck, 1998). This calculates the log likelihood of finding a certain genotype combination in each population and assigns the individual to the population for which it has the highest likelihood.…”