THE HERITABILITY OF EXTERNAL MORPHOLOGY IN DARWIN'S GROUND FINCHES (GEOSPIZA) ON ISLA DAPHNE MAJOR, GALÁPAGOS.

Abstract

Ecologists use avian morphological measurements to develop and test evolutionary theories. The theories are usually based on genetic models, although little is known about the inheritance of such characters. In field studies it is commonly assumed that phenotypic variation closely reflects underlying genetic variation (Grant et al., 1976), while theoreticians sometimes assume that heritabilities are equal to one (Long, 1974). P. R. Grant and his colleagues (Grant et al., 1976; Abbott et al., 1977; Boag and Grant, 1981; Grant, 198 lb) have been studying Darwin's ground finches (Geospiza) in the Galapagos, focusing on relationships between finch morphology and food supplies. Unlike Mendelian characters such as plumage polymorphisms (Mineau and Cooke, 1979), finch morphology involves metric characters and is studied using quantitative genetics (Falconer, 1981). Quantitative genetics describes the phenotypic value of an individual (e.g., its