Characterizing dispersal patterns in a threatened seabird with limited genetic structure
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| Authors: | Hall, LA; Palsboll, PJ; Beissinger, SR; Harvey, JT; Berube, M; Raphael, MG; Nelson, SK; Golightly, RT; Mcfarlane-Tranquilla, L; Newman, SH; Peery, MZ |
| Year: | 2009 |
| Journal: | Molecular Ecology 18: 5074-5085 Article Link (DOI) |
| Title: | Characterizing dispersal patterns in a threatened seabird with limited genetic structure |
| Abstract: | Genetic assignment methods provide an appealing approach for characterizing dispersal patterns on ecological time scales, but require sufficient genetic differentiation to accurately identify migrants and a large enough sample size of migrants to, for example, compare dispersal between sexes or age classes. We demonstrate that assignment methods can be rigorously used to characterize dispersal patterns in a marbled murrelet (Brachyramphus marmoratus) population from central California that numbers approximately 600 individuals and is only moderately differentiated (F-ST similar to 0.03) from larger populations to the north. We used coalescent simulations to select a significance level that resulted in a low and approximately equal expected number of type I and II errors and then used this significance level to identify a population of origin for 589 individuals genotyped at 13 microsatellite loci. The proportion of migrants in central California was greatest during winter when 83% of individuals were classified as migrants compared to lower proportions during the breeding (6%) and post-breeding (8%) seasons. Dispersal was also biased toward young and female individuals, as is typical in birds. Migrants were rarely members of parent-offspring pairs, suggesting that they contributed few young to the central California population. A greater number of migrants than expected under equilibrium conditions, a lack of individuals with mixed ancestry, and a small number of potential source populations (two), likely allowed us to use assignment methods to rigorously characterize dispersal patterns for a population that was larger and less differentiated than typically thought required for the identification of migrants. |
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