title: Reproductive isolation of sympatric morphs in a population of Darwin's finches.
abstract: Recent research on speciation has identified a central role for ecological divergence, which can initiate speciation when (i) subsets of a species or population evolve to specialize on different ecological resources and (ii) the resulting phenotypic modes become reproductively isolated. Empirical evidence for these two processes working in conjunction, particularly during the early stages of divergence, has been limited. We recently described a population of the medium ground finch, Geospiza fortis, that features large and small beak morphs with relatively few intermediates. As in other Darwin's finches of the Galápagos Islands, these morphs presumably diverged in response to variation in local food availability and inter- or intraspecific competition. We here demonstrate that the two morphs show strong positive assortative pairing, a pattern that holds over three breeding seasons and during both dry and wet conditions. We also document restrictions on gene flow between the morphs, as revealed by genetic variation at 10 microsatellite loci. Our results provide strong support for the central role of ecology during the early stages of adaptive radiation.
authors.affiliation: Graduate Program in Organismic and Evolutionary Biology, University of Massachusetts, Amherst, MA 01003, USA. shuber@bio.umass.edu
authors.forename: Sarah K
authors.initials: SK
authors.lastname: Huber
authors.forename: Luis Fernando
authors.initials: LF
authors.lastname: De León
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Hendry
authors.forename: Eldredge
authors.initials: E
authors.lastname: Bermingham
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Podos
mesh_terms: D000818:Animals; D001502:Beak / Q000033:anatomy & histology; D016000:Cluster Analysis; D004484:Ecuador; D046369:Finches / Q000033:anatomy & histology / Q000235:genetics* / Q000502:physiology; D051456:Gene Flow / Q000235:genetics; D049810:Genetic Speciation; D014644:Genetic Variation; D005828:Genetics, Population; D018895:Microsatellite Repeats / Q000235:genetics; D025341:Principal Component Analysis; D012098:Reproduction / Q000502:physiology*; D012726:Sexual Behavior, Animal / Q000502:physiology*