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Type: Journal article
Title: Panmixia supports divergence with gene flow in Darwin's small ground finch, Geospiza fuliginosa, on Santa Cruz, Galápagos Islands
Other Titles: Panmixia supports divergence with gene flow in Darwin's small ground finch, Geospiza fuliginosa, on Santa Cruz, Galapagos Islands
Author: Galligan, T.
Donnellan, S.
Sulloway, F.
Fitch, A.
Bertozzi, T.
Kleindorfer, S.
Citation: Molecular Ecology, 2012; 21(9):2106-2115
Publisher: Wiley
Issue Date: 2012
ISSN: 0962-1083
Statement of
Toby H. Galligan, Stephen C. Donnellan, Frank J. Sulloway, Alison J. Fitch, Terry Bertozzi and Sonia Kleindorfer
Abstract: The divergence-with-gene-flow model of speciation has a strong theoretical basis with a growing number of plausible examples in nature, but remains hotly debated. Darwin's finches of the Galápagos Archipelago have played an important role in our understanding of speciation processes. Recent studies suggest that this group may also provide insights into speciation via divergence with gene flow. On the island of Santa Cruz, recent studies found evidence for adaptive divergence in Darwin's small ground finch, Geospiza fuliginosa, between ecologically contrasting arid and humid zones. Despite the short geographical distance between these zones, strong disruptive selection during low rainfall periods is expected to generate and maintain adaptive divergence. Conversely, during high rainfall periods, when disruptive selection is predicted to be weakened, population divergence in adaptive traits is expected to break down. Because periods of low and high rainfall irregularly alternate, the geographical pattern of adaptive divergence can be assumed to break down and, importantly, regenerate in situ. Here, we use microsatellite allele frequency data to assess the genetic population structure of G. fuliginosa on Santa Cruz. We sample 21 sites and four ecological zones across the island. We reject hypotheses of population substructure linked to ecological and geographical differences among sites in favour of a single panmictic population. Panmixia implies high levels of gene flow within Santa Cruz, which favours selection over genetic drift as a valid process generating phenotypic divergence in G. fuliginosa on Santa Cruz. We discuss how our findings may support classic adaptation, phenotypic plasticity, matching habitat choice or any combination of these three processes.
Keywords: Adaptive divergence; Darwin’s finches; divergence with gene flow; divergent selection; no population structure; panmixia; parapatric divergence; within-island gene flow
Description: Article first published online: 8 MAR 2012
Rights: © 2012 Blackwell Publishing Ltd
RMID: 0030009024
DOI: 10.1111/j.1365-294X.2012.05511.x
Appears in Collections:Earth and Environmental Sciences publications

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