The Taxonomic Status of the Small Ground-Finch, Geospiza (Aves: Emberizidae) of Genovesa Island, Galápagos, and Its Relevance to Interspecific Competition

Vagvolgyi, Joseph

doi:10.2307/4087771

Cited by 4 publications

(6 citation statements)

References 11 publications

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“…A simple answer would be yes, but the situation is made complex by the lack of concordance between phenotypic and genetic variation. The morphological analyses confirm previous studies in showing that the Genovesa population resembles other populations of G. dzfiilis in shape and G.3liginosa in size (Schluter & Grant, 1984a;Vagvolgyi & Vagvolgyi, 1989Schluter et al, 199 1). Analyses of vocalizations show that individuals on Genovesa have (a) features in common with other populations of G. dficilis but not shared by other Geospiza species (buzzy song and high frequencies), and (b) features shared both conspecifically and heterospecifically (whistles and repeated songs).…”

Section: Evohtionav Histov Of the Population On Genovesasupporting

confidence: 89%

“…A simple answer would be yes, but the situation is made complex by the lack of concordance between phenotypic and genetic variation. The morphological analyses confirm previous studies in showing that the Genovesa population resembles other populations of G. dzfiilis in shape and G.3liginosa in size (Schluter & Grant, 1984a;Vagvolgyi & Vagvolgyi, 1989Schluter et al, 199 1 , 1986;, nor do morphological and vocal traits covary completely. Lack of concordance presents a problem when attempting to reconstruct evolutionary history and assess phylogenetic affinities (Patterson, 1987).…”

Section: Evohtionav Histov Of the Population On Genovesasupporting

confidence: 88%

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The allopatric phase of speciation: the sharp-beaked ground finch (Geospiza difficilis) on the Galápagos islands

Grant

Petren

2000

Biological Journal of the Linnean Society

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Using microsatellite DNA variation, morphological measurements and sonagrams made from tape-recordings in the field, we examine the allopatric differentiation of six populations of the sharp-beaked ground finch, Geospiza d&lis, in the Galapagos archipelago. We ask how and why the populations became differentiated, and consider what the differences imply about speciation. An important factor is time; G. dfiilis is one of the phylogenetically oldest species. Populations became differentiated by adapting in beak morphology to different food supplies. Since beak size and shape also function in conspecific mate recognition and choice, the potential for reproductive isolation from sister and parental taxa arose as a correlated effect of natural selection on resource-exploiting traits. This conforms to a standard explanation for the origin of pre-mating isolation as a byproduct of adaptive changes in allopatry without being adaptive itseK However, this explanation is incomplete. Vocal characteristics also differentiated, partly as a result of natural and sexual selection independent of beak size change in environments with different sound transmitting properties. An additional element of chance is indicated by a comparison of closely-related populations on two islands, Wolf and Danvin, that are geographically close, and topographically and floristically similar. The populations have markedly different vocalizations. Morphological characters, vocalizations and genetic traits do not vary concordantly among the six populations. One population (Genovesa) is genetically more similar to other congeneric species. Phenotypic similarities with G. dz@lis are the result of a uniquely long retention of shared ancestral traits. Arguments under the phylogenetic species concept justify recognizing this population as a separate species, Geospiza acutimstris. Under the biological species concept it should remain as currently classified, G. dfiilis.

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Section: Evohtionav Histov Of the Population On Genovesasupporting

confidence: 89%

“…A simple answer would be yes, but the situation is made complex by the lack of concordance between phenotypic and genetic variation. The morphological analyses confirm previous studies in showing that the Genovesa population resembles other populations of G. dzfiilis in shape and G.3liginosa in size (Schluter & Grant, 1984a;Vagvolgyi & Vagvolgyi, 1989Schluter et al, 199 1 , 1986;, nor do morphological and vocal traits covary completely. Lack of concordance presents a problem when attempting to reconstruct evolutionary history and assess phylogenetic affinities (Patterson, 1987).…”

Section: Evohtionav Histov Of the Population On Genovesasupporting

confidence: 88%

The allopatric phase of speciation: the sharp-beaked ground finch (Geospiza difficilis) on the Galápagos islands

Grant

Petren

2000

Biological Journal of the Linnean Society

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“…In addition to difficulties with identifying some individuals, the classification of entire Geospiza populations does not always withstand scrutiny. It has been suggested, for example, that Geo-spiza difficilis on Genovesa Island may be more appropriately classified as G. fuliginosa, based on both song and morphological characteristics (Vagvolgyi and Vagvolgyi 1989). Another example comes from unusually large finch specimens from San Cristobal and Floreana Islands.…”

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confidence: 99%

The Mitochondrial and Nuclear Genetic Homogeneity of the Phenotypically Diverse Darwin's Ground Finches

Freeland

Boag

1999

Evolution

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The most extensively studied group of Darwin's finches is the genus Geospiza, the ground finches, and yet little is known about the evolutionary history and genetic relationships of these birds. Studies using either allozyme or morphological data have been unable to resolve relationships between the six species and numerous populations of ground finches. In this paper we report the results of a study using mitochondrial control region and nuclear internal transcribed spacer (ITS) 1 sequence data. The differentiation of the ground finch species based on morphological data is not reflected in either mitochondrial or nuclear DNA sequence phylogenies. Furthermore, there is little concordance between the mitochondrial haplotypes and ITS alleles found within individuals. We suggest that the absence of species-specific lineages can be attributed to ongoing hybridization involving all six species of Geospiza. There are no long term selective pressures against hybridization within this genus, and therefore a genetically homogenous genus may be maintained indefinitely. Hybridization has apparently played a role in the adaptive radiation of Darwin's finches.

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“…For example, song differences (Ratcliffe, ) and song discrimination (Ratcliffe & Grant, ) are statistically stronger between sympatric species pairs than between allopatric species pairs. However, countering this trend, Grant () reported that female G. conirostris on Genovesa avoid mates with songs similar to their fathers, which Goodale & Podos () suggest is a result of selection to avoid inbreeding (see also Vagvolgyi & Vagvolgyi, ).…”

Section: Species Limits and The Evidencementioning

confidence: 99%

“…). An example of this process can be found in the analysis by Vagvolgyi & Vagvolgyi (, p. 147): ‘… Genovesa supports G. difficilis which, in the absence of the competing species G. fuliginosa , underwent profound changes in its diet and morphology to become deceptively similar to the absent competitor.’…”

Section: Why Have Ground Finch Ecomorphs Not Become Species?mentioning

confidence: 99%

Sisyphean evolution in Darwin's finches

McKay

Zink

2014

Biological Reviews

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The trajectory of speciation involves geographic isolation of ancestral populations followed by divergence by natural selection, genetic drift or sexual selection. Once started, the process may experience fits and starts, as sometimes diverging populations intermittently reconnect. In theory populations might cycle between stages of differentiation and never attain species status, a process we refer to as Sisyphean evolution. We argue that the six putative ground finch species (genus Geospiza) of the Galápagos Islands represent a dramatic example of Sisyphean evolution that has been confused with the standard model of speciation. The dynamic environment of the Galápagos, closely spaced islands, and frequent dispersal and introgression have prevented the completion of the speciation process. We suggest that morphological clusters represent locally adapted ecomorphs, which might mimic, and have been confused with, species, but these ecomorphs do not form separate gene pools and are ephemeral in space and time. Thus the pattern of morphological, behavioural and genetic variation supports recognition of a single species of Geospiza, which we suggest should be recognized as Darwin's ground finch (Geospiza magnirostris). We argue that instead of providing an icon of insular speciation and adaptive radiation, which is featured in nearly every textbook on evolutionary biology, Darwin's ground finch represents a potentially more interesting phenomenon, one of transient morphs trapped in an unpredictable cycle of Sisyphean evolution. Instead of revealing details of the origin of species, the mechanisms underlying the transient occurrence of ecomorphs provide one of the best illustrations of the antagonistic effects of natural selection and introgression.

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The Taxonomic Status of the Small Ground-Finch, Geospiza (Aves: Emberizidae) of Genovesa Island, Galápagos, and Its Relevance to Interspecific Competition

Cited by 4 publications

References 11 publications

The allopatric phase of speciation: the sharp-beaked ground finch (Geospiza difficilis) on the Galápagos islands

The allopatric phase of speciation: the sharp-beaked ground finch (Geospiza difficilis) on the Galápagos islands

The Mitochondrial and Nuclear Genetic Homogeneity of the Phenotypically Diverse Darwin's Ground Finches

Sisyphean evolution in Darwin's finches

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