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

Abstract

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.

Molecular data and distribution dynamics indicate a recent and incomplete separation of manakins species of the genus Antilophia (Aves: Pipridae) in response to Holocene climate change

“…This hypothesis is supported by the F ST values and the p distances recorded between the two populations (Table ), which indicate an absence of structuring. Studies of other bird species have shown that morphological variation can become differentiated relatively rapidly under selection pressure, before neutral markers can coalesce towards monophyly (Freeland and Boag , Campagna et al , Campagna et al ). This may coincide with the ‘divergence stages’ proposed by Omland et al (), where two isolated populations may pass through a series of stages of differentiation before they become valid species with well‐defined molecular profiles.…”

“…This may coincide with the ‘divergence stages’ proposed by Omland et al (), where two isolated populations may pass through a series of stages of differentiation before they become valid species with well‐defined molecular profiles. The differentiation of the plumage coloration in the two Antilophia species is another example of the relatively rapid diversification of phenotypic traits in the context of the incomplete separation of lineages (Freeland and Boag , Campagna et al ). These species thus offer an important opportunity for the understanding of the genetic basis for the selection of new adaptive traits through the identification of candidate genes by genomic scanning (Limichhaney et al , Toews et al , Vijay et al ).…”

Comparative landscape genetics and the adaptive radiation of Darwin's finches: the role of peripheral isolation

“…Recent attempts to reconstruct the evolutionary history of Darwin's finches with molecular markers have met with limited success. Studies of mitochondrial (Freeland & Boag 1999a, b; Sato et al . 1999) and nuclear (Freeland & Boag 1999a) sequence variation have been unable to resolve relationships among most species.…”

Mitochondrial DNA diversification among the subspecies of the Silver and Kalij Pheasants, Lophura nycthemera and L. leucomelanos, Phasianidae

“…It appears that we have no nuclear copy of the cyt b because all sequences were aligned without problem (Kidd & Friesen 1998), and no stop codon appears inside. The structure of the CR appears to be conserved (Randi & Lucchini 1998, Freeland & Boag 1999).…”