Mitochondrial DNA Phylogeography of the North American Brown Bear and Implications for Conservation

Abstract

The historical distribution of the brown bear ( Ursus arctos ) in North America included Alaska, western Canada, the western and midwestern states, plus northern Mexico. Currently, the brown bear is limited to Alaska, the Canadian provinces of the Yukon, Northwest Territories, British Columbia, and Alberta, and six threatened subpopulations in the lower 48 states. To examine the evolutionary history of U. arctos in North America and to assess the genetic divergence between individuals from different geographic regions, we obtained 294 nucleotides of mitochondrial DNA sequence data from the control region for 317 free-ranging brown bears. Twenty-eight unique sequences, or mitochondrial DNA haplotypes were detected. The average sequence divergence between haplotypes was high (4.3%), and some haplotypes differed by as many as 23 nucleotides. Phylogenetic analyses using maximum parsimony revealed four major mitochondrial DNA phylogeographic groups, or clades. The significant phylogeographic structure detected in brown bears strongly contrasts with results obtained for other large carnivores and suggests limited female-mediated gene flow. The mitochondrial DNA phylogeographic clades do not correlate with taxonomic classifications for U. arctos , and we hypothesize that the clades were formed prior to migration of this species into North America. We suggest evolutionarily significant units for conservation in three Filogenia del ADN Mitocondrial del Oso Café de Norte América y sus Implicaciones en la Conservación Resumen: La distribución histórica del oso caf é ( Ursus arctos ) en Norte Am é ica includía Alaska, oeste de Canada, oeste y medio oeste de los Estados Unidos y Norte de M é xico. Actualmete, el oso caf é esta limitado a Alaska, las provincias Canadienses de Yukon, Northwest territories, British Columbia, Alberta y seis subpoblaciones amenazadas en 48 estados de los Estados Unidos. Obtuvimos datos de secuencias de 294 nucleótidos de ADN mitocondrial de la región control de 317 osos cafes para examinar la historia evolutiva de U. arctos en Norte Am é rica y evaluar la divergencia gen é tica entre individuos de diferentes regiones geográficas. Fueron detectadas veintiocho secuencias únicas o haplotipos de ADN mitocondrial. El porcentaje de secuencia divergente entre haplotipos fue alto (4.3%) y algunos haplotipos difirieron por tantos como 23 nucleótidos. Análisis filogen é ticos usando maxima parsimonia revelaron cuatro grupos mayores de ADN mitocondrial filogeográfico. La estructura filogeografica significativa detectada en osos caf é s contrasta fuertemente con resultados obtenidos de otros carnivoros mayores y sugiere flujo genético limitado, mediado por las hembras. Los grupos de ADN mitocondrial filogeográfico no se correlacionan con clasificaciones taxonómicas de U. arctos , nosotros hipotetizamos que los grupos fueron formados antes de las migraciones de esta especie hacia Norte América. Sugerimos unidades evolutivamente significativas para su conservación en tres regiones geográficas: 1) las islas Admi...

Genetic diversity of endangered brown bear (Ursus arctos) populations at the crossroads of Europe, Asia and Africa

“…Previously, only three individuals native to the region had been sampled for mtDNA sequences (Talbot & Shields, 1996;Miller et al, 2006). In comparison, analyses of 317 North American brown bears revealed the existence of at least 28 matrilineages (Waits et al, 1998). Taken together, these ten individuals harbour at least six different mtDNA haplotypes [Ha1-Ha4 (this study); GB28 (Talbot & Shields, 1996); Individual 49 (Miller et al, 2006)].…”

“…Control region sequences from modern brown bears covering our entire fragment of 267-271 bp were obtained from Taberlet & Bouvet (1994), Waits et al (1998), Masuda et al (1998) and Matsuhashi et al (1999; see Appendix S1 in Supporting Information for accession numbers). Cyt b sequences from modern brown bears were obtained from Talbot & Shields (1996), Matsuhashi et al (1999), Delisle & Strobeck (2002) and Calvignac et al (2008; Appendix S1).…”

“…To assess the genetic diversity of brown bears (Ursus arctos), mitochondrial variation has been surveyed in European and North American populations, generally revealing the existence of allopatric clades (Taberlet & Bouvet, 1992Randi et al, 1994;Kohn et al, 1995;Talbot & Shields, 1996;Waits et al, 1998;Saarma et al, 2007). Relatively few studies have concentrated on Asian populations (Masuda et al, 1998;Matsuhashi et al, 1999).…”

Large‐scale migrations of brown bears in Eurasia and to North America during the Late Pleistocene

“…The eastern clade present in Europe (3a) divides further into subclades 3a1 and 3a2 (Hirata et al., ). Subclade 3a1 extends from Fennoscandia to East Asia, and into North America (Keis et al., ; Korsten et al., ; Murtskhvaladze, Gavashelishvili, & Tarkhnishvili, ; Saarma & Kojola, ; Waits, Talbot, Ward, & Shields, ). Other clades in Asia appear geographically rather confined: clade 3a2 to central Hokkaido, 3b to eastern Hokkaido, the Russian Far East and southern Siberia (Tomsk region), clade 4 to southern Hokkaido, and clade 5 to Tibet (Guskov, Sheremeteva, Seredkin, & Kryukov, ; Hirata et al., ; Salomashkina, Kholodova, Tutenkov, Moskvitina, & Erokhin, ).…”

Phylogeography and mitochondrial diversity of extirpated brown bear (Ursus arctos) populations in the contiguous United States and Mexico

“…1995). In North America, where occupation is much more recent and a major ice‐age must have driven a shifting distributional history, there is also a remarkable level of mtDNA genetic structure (Talbot & Shields 1996; Waits et al . 1998).…”