title: Demographic mechanisms underpinning genetic assimilation of remnant groups of a large carnivore.
abstract: Current range expansions of large terrestrial carnivores are occurring following human-induced range contraction. Contractions are often incomplete, leaving small remnant groups in refugia throughout the former range. Little is known about the underlying ecological and evolutionary processes that influence how remnant groups are affected during range expansion. We used data from a spatially explicit, long-term genetic sampling effort of grizzly bears (Ursus arctos) in the Northern Continental Divide Ecosystem (NCDE), USA, to identify the demographic processes underlying spatial and temporal patterns of genetic diversity. We conducted parentage analysis to evaluate how reproductive success and dispersal contribute to spatio-temporal patterns of genetic diversity in remnant groups of grizzly bears existing in the southwestern (SW), southeastern (SE) and east-central (EC) regions of the NCDE. A few reproductively dominant individuals and local inbreeding caused low genetic diversity in peripheral regions that may have persisted for multiple generations before eroding rapidly (approx. one generation) during population expansion. Our results highlight that individual-level genetic and reproductive dynamics play critical roles during genetic assimilation, and show that spatial patterns of genetic diversity on the leading edge of an expansion may result from historical demographic patterns that are highly ephemeral.
authors.affiliation: Northern Rocky Mountain Science Center, US Geological Survey, 38 Mather Drive, PO Box 169, West Glacier, MT 59936, USA nmikle@usgs.gov.
authors.forename: Nate
authors.identifier: 0000-0002-6529-8210
authors.initials: N
authors.lastname: Mikle
authors.affiliation: Northern Rocky Mountain Science Center, US Geological Survey, 38 Mather Drive, PO Box 169, West Glacier, MT 59936, USA.
authors.forename: Tabitha A
authors.identifier: 0000-0001-5145-2400
authors.initials: TA
authors.lastname: Graves
authors.affiliation: Northern Rocky Mountain Science Center, US Geological Survey, 38 Mather Drive, PO Box 169, West Glacier, MT 59936, USA.
authors.forename: Ryan
authors.initials: R
authors.lastname: Kovach
authors.affiliation: Northern Rocky Mountain Science Center, US Geological Survey, 38 Mather Drive, PO Box 169, West Glacier, MT 59936, USA.
authors.forename: Katherine C
authors.initials: KC
authors.lastname: Kendall
authors.affiliation: University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Amy C
authors.initials: AC
authors.lastname: Macleod
mesh_terms: D000818:Animals; D017753:Ecosystem; D014644:Genetic Variation; D005828:Genetics, Population; D007178:Inbreeding; D009656:North America; D062211:Spatio-Temporal Analysis; D001503:Ursidae / Q000235:genetics*
keywords: dispersal; genetic diversity; migration; parentage; range expansion; reproduction