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A geometric morphometric appraisal of beak shape in Darwin’s finches
Author(s) -
FOSTER D. J.,
PODOS J.,
HENDRY A. P.
Publication year - 2008
Publication title -
journal of evolutionary biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.289
H-Index - 128
eISSN - 1420-9101
pISSN - 1010-061X
DOI - 10.1111/j.1420-9101.2007.01449.x
Subject(s) - beak , biology , morphometrics , sympatric speciation , allometry , ecomorphology , zoology , ecology , habitat
Beak size and shape in Darwin’s finches have traditionally been quantified using a few univariate measurements (length, depth, width). Here we show the improved inferential resolution of geometric morphometric methods, as applied to three hierarchical levels: (i) among seven species on Santa Cruz Island, (ii) among different sites on Santa Cruz for a single species ( Geospiza fortis ), and (iii) between large and small beak size morphs of G. fortis at one site (El Garrapatero). Our results support previous studies in finding an axis of shape variation (long/shallow/pointy vs. short/deep/blunt) that separates many of the species. We also detect additional differences among species in the relative sizes and positions of the upper and lower mandibles and in curvature of the mandibles. Small‐scale, but potentially relevant, shape variation was also detected among G. fortis from different sites and between sympatric beak size morphs. These results suggest that adaptation to different resources might contribute to diversification on a single island.