GENETIC DIFFERENTIATION AND BIOGEOGRAPHY OF THE MASKED SHREW IN ATLANTIC CANADA

Citation
Dt. Stewart et Aj. Baker, GENETIC DIFFERENTIATION AND BIOGEOGRAPHY OF THE MASKED SHREW IN ATLANTIC CANADA, Canadian journal of zoology, 70(1), 1992, pp. 106-114
Citations number
53
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Zoology
Journal title
ISSN journal
0008-4301
Volume
70
Issue
1
Year of publication
1992
Pages
106 - 114
Database
ISI
SICI code
0008-4301(1992)70:1<106:GDABOT>2.0.ZU;2-3
Abstract
The masked shrew (Sorex cinereus) occurs naturally on a number of smal l to large islands in Atlantic Canada, and 22 individuals were introdu ced into Newfoundland from New Brunswick in 1958. Genetic variation de tected by protein electrophoresis of 34 presumptive gene loci was assa yed in five island and three mainland populations from this region to compare rates of differentiation among the populations and to investig ate genetic relationships among populations in the context of historic al biogeographic events constructed from the geological literature. We found considerable differentiation among populations which can be att ributed to different origins for the populations in the post-Wisconsin glacial phase, and to apparently rapid evolution in small isolated po pulations, especially for the small island of Bon Portage. Nova Scotia . Allele frequencies are more heterogeneous among the island populatio ns and exhibit classic neutral behaviour in that rare alleles are abse nt and shifts in allele frequency occur to either side of mainland mea ns. There is no correlation of allele frequencies with geographic prox imity of populations as might be expected under selectively based clin es, or, alternatively, under isolation by distance expected with a dif fusive wave of colonization in the region. Instead, the genetic data a re compatible with random drift of neutral alleles in populations of v arious effective sizes isolated from each other by rising sea levels i n the last 20 000 - 5000 years. The considerable divergence that has o ccurred among the island populations (F(ST) = 0.238) may be indicative of incipient speciation or subspeciation. This subdivision does not a ppear to be founder-induced but is more likely the product of gradual drift in and interruption of homogenizing gene flow among relict popul ations that existed during the Pleistocene.