Platyspiza crassirostris

About: Platyspiza crassirostris is a research topic. Over the lifetime, 4 publications have been published within this topic receiving 261 citations.

A phylogeny of Darwin's finches based on microsatellite DNA length variation

Abstract: Allele length variation at 16 microsatellite loci was used to estimate the phylogeny of 13 out of the 14 species of Darwin's finches. The resulting topology was similar to previous phylogenies based on morphological and allozyme variation. An unexpected result was that genetic divergence among Galapagos Island populations of the warbler finch (Certhidea olivacea) predates the radiation of all other Darwin's finches. This deep split is surprising in view of the relatively weak morphological differentiation among Certhidea populations and supports the hypothesis that the ancestor of all Darwin's finches was phenotypically similar to Certhidea. The results also resolve a biogeographical problem: the Cocos Island finch evolved after the Galapagos finch radiation was under way, supporting the hypothesis that this distant island was colonized from the Galapagos Islands. Monophyletic relationships are supported for both major groups, the ground finches (Geospiza) and the tree finches (Camarhynchus and Cactospiza), although the vegetarian finch (Platyspiza crassirostris) appears to have diverged prior to the separation of ground and tree finches. These results demonstrate the use of microsatellites for reconstructing phylogenies of closely related species and interpreting their evolutionary and biogeographic histories.

A New Perspective on The Evolutionary History of Darwin's Finches

Abstract: The 13 species of finches found on the Galapagos Islands, and the one species from Cocos Island, together collectively known as Darwin's finches, are one of the better-studied groups of birds. Much has been learned about their ecology, behavior, and the short-term effects of natural selection (Lack 1947, Bowman 1961, Grant 1999). The four species of tree finch (Camarhynchus), six species of ground finch (Geospiza), the tool-using Woodpecker Finch (Cactospiza pallida), the Vegetarian Finch (Platyspiza crassirostris), the Warbler Finch (Certhidea olivacea), and the finch on Cocos Island (Pinaroloxias inornata) appear to fill different ecological roles via differentiation of bill size and shape (Grant and Grant 2002). In fact, most authors consider Darwin's finches to be a classic example of an adaptive radiation, owing to the great diversity in bill form and ecological habit that presumably evolved in a relatively short time. For example, Petren et al. (1999:321) noted, "Species in this group show adaptive variation in beak size, beak shape and body size that is more typical of differences among [taxonomic] families of birds... (boldface added). Taxonomic History.-Darwin originally collected the finches from the Galapagos, not realizing what an evolutionary gold mine they would become (Sulloway 1982). In fact, he was not careful about labeling specimens as to the island from which a specimen was obtained, thus obscuring taxonomic boundaries. Subsequent work with better-labeled specimens revealed taxonomically significant patterns of variation. Gould (1837) recognized that different species existed in the collections from the Darwin expedition. However, Gould was unable to produce a stable classification. Since Gould's time, many of the major figures in avian taxonomy have published differing classifications. The succession of revisionary efforts attests to the difficult nature of classifying phenotypic variation among the finches. Although the species show considerable morphological diversity, many in fact are notoriously difficult to identify in the field (especially females and immatures). Populations from different species and islands overlap in morphometric space (Grant 1981).

Invasive Parasites and the Fate of Darwin's Finches in the Galapagos Islands: The Case of the Vegetarian Finch (Platyspiza crassirostris)

Abstract: The Vegetarian Finch, Platyspiza crassirostris, is a relatively unstudied Darwin's finch that appears to be in decline in the Galapagos Islands. We monitored 11 nests of Vegetarian Finches during 2013 and 2014 on Santa Cruz Island, Galapagos, and found that 10 of these were infested with an invasive parasitic fly, Philornis downsi. This is the first report of P. downsi attacking this bird species. The number of P. downsi in nests of Vegetarian Finches was higher than for other Darwin's finch species, but nestling mortality was relatively low. We hypothesize that both of these trends may be related to fact that the Vegetarian Finch is one of the largest-bodied species of Darwin's finches. We also consider the conservation implications of P. downsi parasitism for populations of vegetarian finches and other Darwin's finch species in the Galapagos Islands.

Dispersal of fern spores by Galápagos finches

Abstract: Fern sporangia may provide an important source of energy for bird species, which in turn can act as potential dispersers of viable spores. This study reports the first case of fern spore dispersal by land birds. We document the consumption of fern sporangia and evaluate the potential spore dispersal by Galapagos finches on Santa Cruz Island. Overall, 18% of the 34 sampled individuals of three finch species, the Vegetarian Finch (Platyspiza crassirostris), the Small Ground Finch (Geospiza fuliginosa) and the Medium Ground Finch (Geospiza fortis), were found to disperse viable spores of two native ferns, Asplenium auritum and Asplenium feei.