Reproductive isolation of sympatric morphs in a population of Darwin's finches.
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.
Huber
Sarah K
SK
Graduate Program in Organismic and Evolutionary Biology, University of Massachusetts, Amherst, MA 01003, USA. shuber@bio.umass.edu
De León
Luis Fernando
LF
Hendry
Andrew P
AP
Bermingham
Eldredge
E
Podos
Jeffrey
J
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*