IngentaConnect Integrative use of spatial, genetic, and demographic analyses for...

Authors: BOULET, MARYLÈNE; COUTURIER, SERGE; CÔTÉ, STEEVE D.; OTTO, ROBERT D.; BERNATCHEZ, LOUIS¹

Source: Molecular Ecology, Volume 16, Number 20, October 2007 , pp. 4223-4240(18)

Abstract:

Genetic differentiation is generally assumed to be low in highly mobile species, but this simplistic view may obscure the complex conditions and mechanisms allowing genetic exchanges between specific populations. Here, we combined data from satellite-tracked migratory caribou (Rangifer tarandus), microsatellite markers, and demographic simulations to investigate gene flow mechanisms between seven caribou herds of eastern Canada. Our study included one montane, two migratory, and four sedentary herds. Satellite-tracking data indicated possibilities of high gene flow between migratory herds: overlap of their rutting ranges averaged 10% across years and 9.4% of females switched calving sites at least once in their lifetime. Some migratory individuals moved into the range of the sedentary herds, suggesting possibilities of gene flow between these herds. Genetic differentiation between herds was weak but significant (F_ST = 0.015): migratory and montane herds were not significantly distinct (F_ST all ≤ 0.005), whereas sedentary herds were more differentiated (F_ST = 0.018-0.048). Geographical distances among sedentary herds limited gene flow. Historical estimates of gene flow were higher from migratory herds into sedentary herds (4Nm all > 9) than vice-versa (4Nm all < 5), which suggests migratory herds had a demographic impact on sedentary herds. Demographic simulations showed that an effective immigration rate of 0.0005 was sufficient to obtain the empirical F_ST of 0.015, while a null immigration rate increased the simulated F_ST to > 0.6. In conclusion, the weak genetic differentiation between herds cannot be obtained without some genetic exchanges among herds, as demonstrated by genetic and spatial data.

Keywords: caribou; demographic simulations; gene flow; metapopulation; microsatellite; population structure; Rangifer tarandus; satellite-tracking

Document Type: Research article

DOI: 10.1111/j.1365-294X.2007.03476.x

Affiliations: 1: Département de Biologie, Université Laval, Québec, QC, Canada G1K 7P4,

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Integrative use of spatial, genetic, and demographic analyses for investigating genetic connectivity between migratory, montane, and sedentary caribou herds