Publications

darwin's finches: population variation and natural selection.	van valen's model, which relates morphological variation to ecological variation in an adaptive scheme, was investigated with individually marked and measured darwin's finches on two adjacent galápagos islands, santa cruz and daphne major. results show that environmental heterogeneity is correlated with large continuous, morphological variation: variation in bill dimensions of geospiza fortis is greater on santa cruz than on daphne, as is environmental heterogeneity. within populations of this s ...	1976	1061123
isospora daphnensis n. sp. (apicomplexa: eimeriidae) from the medium ground finch (geospiza fortis) from the galapagos islands.	in march and april 1987 fecal samples from 237 nestling birds, including 199 from 85 nest sites of geospiza fortis, 23 from 12 nest sites of geospiza scandens, 6 from 2 nest sites of geospiza magnirostris, and 9 from 2 nest sites of hybrids involving geospiza fuliginosa and g. fortis, were collected from daphne major in the galapagos archipelago and examined for coccidia. only 3 of 4 nestlings from 1 nest site of g. fortis (1.5%) had oocysts in their feces. two of the 3 infected nestlings had co ...	1990	2299524
unpredictable evolution in a 30-year study of darwin's finches.	evolution can be predicted in the short term from a knowledge of selection and inheritance. however, in the long term evolution is unpredictable because environments, which determine the directions and magnitudes of selection coefficients, fluctuate unpredictably. these two features of evolution, the predictable and unpredictable, are demonstrated in a study of two populations of darwin's finches on the galápagos island of daphne major. from 1972 to 2001, geospiza fortis (medium ground finch) an ...	2002	11976447
vocal mechanics in darwin's finches: correlation of beak gape and song frequency.	recent studies of vocal mechanics in songbirds have identified a functional role for the beak in sound production. the vocal tract (trachea and beak) filters harmonic overtones from sounds produced by the syrinx, and birds can fine-tune vocal tract resonance properties through changes in beak gape. in this study, we examine patterns of beak gape during song production in seven species of darwin's finches of the galápagos islands. our principal goals were to characterize the relationship between ...	2004	14718504
evolution of character displacement in darwin's finches.	competitor species can have evolutionary effects on each other that result in ecological character displacement; that is, divergence in resource-exploiting traits such as jaws and beaks. nevertheless, the process of character displacement occurring in nature, from the initial encounter of competitors to the evolutionary change in one or more of them, has not previously been investigated. here we report that a darwin's finch species (geospiza fortis) on an undisturbed galápagos island diverged in ...	2006	16840700
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 for ...	2007	17504742
disruptive selection in a bimodal population of darwin's finches.	a key part of the ecological theory of adaptive radiation is disruptive selection during periods of sympatry. some insight into this process might be gained by studying populations that are bimodal for dual-context traits, i.e. those showing adaptive divergence and also contributing to reproductive isolation. a population meeting these criteria is the medium ground finch (geospiza fortis) of el garrapatero, santa cruz island, galápagos. we examined patterns of selection in this population by rel ...	2009	18986971
the secondary contact phase of allopatric speciation in darwin's finches.	speciation, the process by which two species form from one, involves the development of reproductive isolation of two divergent lineages. here, we report the establishment and persistence of a reproductively isolated population of darwin's finches on the small galápagos island of daphne major in the secondary contact phase of speciation. in 1981, an immigrant medium ground finch (geospiza fortis) arrived on the island. it was unusually large, especially in beak width, sang an unusual song, and c ...	2009	19918081
acoustic discrimination of sympatric morphs in darwin's finches: a behavioural mechanism for assortative mating?	populations with multiple morphological or behavioural types provide unique opportunities for studying the causes and consequences of evolutionary diversification. a population of the medium ground finch (geospiza fortis) at el garrapatero on santa cruz island, galápagos, features two beak size morphs. these morphs produce acoustically distinctive songs, are subject to disruptive selection and mate assortatively by morph. the main goal of the present study was to assess whether finches from this ...	2010	20194166
divergence with gene flow as facilitated by ecological differences: within-island variation in darwin's finches.	divergence and speciation can sometimes proceed in the face of, and even be enhanced by, ongoing gene flow. we here study divergence with gene flow in darwin's finches, focusing on the role of ecological/adaptive differences in maintaining/promoting divergence and reproductive isolation. to this end, we survey allelic variation at 10 microsatellite loci for 989 medium ground finches (geospiza fortis) on santa cruz island, galápagos. we find only small genetic differences among g. fortis from dif ...	2010	20194167
conspecific versus heterospecific gene exchange between populations of darwin's finches.	this study addresses the extent and consequences of gene exchange between populations of darwin's finches. four species of ground finches (geospiza) inhabit the small island of daphne major in the centre of the galápagos archipelago. we undertook a study of microsatellite dna variation at 16 loci in order to quantify gene flow within species owing to immigration and between species owing to hybridization. a combination of pedigrees of observed breeders and assignments of individuals to populatio ...	2010	20194169
multiple lineages of avian malaria parasites (plasmodium) in the galapagos islands and evidence for arrival via migratory birds.	haemosporidian parasites in the genus plasmodium were recently detected through molecular screening in the galapagos penguin (spheniscus mendiculus). we summarized results of an archipelago-wide screen of 3726 endemic birds representing 22 species for plasmodium spp. through a combination of molecular and microscopy techniques. three additional plasmodium lineages were present in galapagos. lineage a-infected penguins, yellow warblers (setophaga petechia aureola), and one medium ground finch (ge ...	2013	24033638