TY - JOUR
T1 - Isolation by distance among California sea lion populations in Mexico
T2 - Redefining management stocks
AU - González-Suárez, M.
AU - Flatz, R.
AU - Aurioles-Gamboa, D.
AU - Hedrick, P. W.
AU - Gerber, Leah
PY - 2009/3
Y1 - 2009/3
N2 - Understanding the spatial structure of a population is critical for effective assessment and management. However, direct observation of spatial dynamics is generally difficult, particularly for marine mammals. California sea lions (Zalophus californianus) are polygynous pinnipeds distributed along the Pacific coast of North America. The species' range has been subdivided into three management stocks based on differences in mitochondrial DNA, but to date no studies have considered nuclear genetic variation, and thus we lack a comprehensive understanding of gene flow patterns among sea lion colonies. In light of recent population declines in the Gulf of California, Mexico, it is important to understand spatial structure to determine if declining sea lion colonies are genetically isolated from others. To define population subdivision and identify sex biases in gene flow, we analysed a 355-bp sequence of the mitochondrial DNA control region and 10 polymorphic microsatellite loci from 355 tissue samples collected from six colonies distributed along Mexican waters. Using a novel approach to estimate sex biases in gene flow, we found that male sea lions disperse on average 6.75 times more frequently than females. Analyses of population subdivision strongly suggest a pattern of isolation by distance among colonies and challenge current stock definitions. Based on these results, we propose an alternative classification that identifies three Mexican management units: Upper Gulf of California, Southern Baja Peninsula, and Upper Pacific Coast of Baja. This revised classification should be considered in future assessment and management of California sea lion populations in Mexican waters.
AB - Understanding the spatial structure of a population is critical for effective assessment and management. However, direct observation of spatial dynamics is generally difficult, particularly for marine mammals. California sea lions (Zalophus californianus) are polygynous pinnipeds distributed along the Pacific coast of North America. The species' range has been subdivided into three management stocks based on differences in mitochondrial DNA, but to date no studies have considered nuclear genetic variation, and thus we lack a comprehensive understanding of gene flow patterns among sea lion colonies. In light of recent population declines in the Gulf of California, Mexico, it is important to understand spatial structure to determine if declining sea lion colonies are genetically isolated from others. To define population subdivision and identify sex biases in gene flow, we analysed a 355-bp sequence of the mitochondrial DNA control region and 10 polymorphic microsatellite loci from 355 tissue samples collected from six colonies distributed along Mexican waters. Using a novel approach to estimate sex biases in gene flow, we found that male sea lions disperse on average 6.75 times more frequently than females. Analyses of population subdivision strongly suggest a pattern of isolation by distance among colonies and challenge current stock definitions. Based on these results, we propose an alternative classification that identifies three Mexican management units: Upper Gulf of California, Southern Baja Peninsula, and Upper Pacific Coast of Baja. This revised classification should be considered in future assessment and management of California sea lion populations in Mexican waters.
KW - Gulf of California
KW - Microsatellites
KW - Mitochondrial DNA
KW - Pinniped
KW - Population structure
KW - Sex-biased dispersal
KW - Zalophus californianus
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U2 - 10.1111/j.1365-294X.2009.04093.x
DO - 10.1111/j.1365-294X.2009.04093.x
M3 - Article
C2 - 19226320
AN - SCOPUS:61649095015
SN - 0962-1083
VL - 18
SP - 1088
EP - 1099
JO - Molecular ecology
JF - Molecular ecology
IS - 6
ER -