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Genetic and phenotypic divergence in an island bird: isolation by distance, by colonization or by adaptation?
Author(s) -
Spurgin Lewis G.,
Illera Juan Carlos,
Jorgensen Tove H.,
Dawson Deborah A.,
Richardson David S.
Publication year - 2014
Publication title -
molecular ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.619
H-Index - 225
eISSN - 1365-294X
pISSN - 0962-1083
DOI - 10.1111/mec.12672
Subject(s) - biology , biological dispersal , isolation by distance , genetic divergence , evolutionary biology , adaptation (eye) , colonization , passerine , archipelago , founder effect , genetic drift , local adaptation , reproductive isolation , genetic structure , ecology , genetic variation , genetic diversity , genetics , allele , population , gene , demography , neuroscience , sociology , haplotype
Abstract Discerning the relative roles of adaptive and nonadaptive processes in generating differences among populations and species, as well as how these processes interact, is a fundamental aim in biology. Both genetic and phenotypic divergence across populations can be the product of limited dispersal and gradual genetic drift across populations (isolation by distance), of colonization history and founder effects (isolation by colonization) or of adaptation to different environments preventing migration between populations (isolation by adaptation). Here, we attempt to differentiate between these processes using island populations of B erthelot's pipit ( A nthus berthelotii ), a passerine bird endemic to three A tlantic archipelagos. Using microsatellite markers and approximate Bayesian computation, we reveal that the northward colonization of this species ca. 8500 years ago resulted in genetic bottlenecks in the colonized archipelagos. We then show that high levels of genetic structure exist across archipelagos and that these are consistent with a pattern of isolation by colonization, but not with isolation by distance or adaptation. Finally, we show that substantial morphological divergence also exists and that this is strongly concordant with patterns of genetic structure and bottleneck history, but not with environmental differences or geographic distance. Overall, our data suggest that founder effects are responsible for both genetic and phenotypic changes across archipelagos. Our findings provide a rare example of how founder effects can persist over evolutionary timescales and suggest that they may play an important role in the early stages of speciation.