干旱区生态环境知识资源中心

We collected 474 specimens of male Rufous-collared Sparrows (Zonotrichia capensis) from 24 sites in northwestern Argentina. Four samples were obtained from each of six habitats: lowland chaco thornscrub, transition forest, montane woodland, montane grassland, Monte desert scrub, and puna high-altitude scrub. Puna birds (Z. c. pulacayensis) were differentiated both genetically and morphologically from all other birds in the sample (Z. c. hypoleuca). However, the steepness and location of the clines for these two character types were substantially different. An abrupt cline in PGM-1 allozyme frequencies was apparent in the extreme northwest of our study area, while clines in morphological features (primarily body size) were gradual and extended much further southward. Among nonpuna samples (20 sites; Z. c. hypoleuca), patterns of intersite differentiation in morphological and allozyme characters were unrelated. Partial Mantel’s tests showed that, among these samples, both degree of difference in habitat structure and linear geographic distance are important correlates of among-site morphological differentiation. Similar tests demonstrated that neither of these two environmental factors is related statistically to genetic differentiation among population.