Birds of Indian Subcontinent

Morphological Adaptation with No Mitochondrial DNA Differentiation in the Coastal Plain Swamp Sparrow

Publication Type:Journal Article
Year of Publication:1998
Authors:Greenberg, R, Cordero, PJ, DROEGE, SAM, Fleischer, RC
Journal:The Auk
Date Published:1998
ISBN Number:00048038
Keywords:Corvidae, Corvus, Corvus corone, Emberizidae, Melospiza, Melospiza georgiana, Zonotrichia, Zonotrichia georgiana
Abstract:We estimated genetic differentiation between morphologically distinct tidal marsh populations of Swamp Sparrows (Melospiza georgiana nigrescens) and the more widespread inland populations (M. g. georgiana and M. g. ericrypta). The tidal marsh populations are consistently grayer with more extensive black markings (particularly in the crown), and their bills are larger. These differences are variously shared with other species of salt marsh birds and small mammals. We analyzed mitochondrial DNA sequences (5′ end of control region, COII/t-lys/ATPase8, and ND2) of Swamp Sparrows and found low levels of genetic variation and no evidence of geographic structure. These results suggest a rapid and recent geographic expansion of Swamp Sparrows from restricted Pleistocene populations. Morphological differentiation has occurred without long-term genetic isolation, suggesting that selection on the divergent traits is intense. The grayer and more melanistic plumage is probably cryptic coloration for foraging on tidal mud, which tends to be grayish as a result of the formation of iron sulfides, rather than iron oxides, under anaerobic conditions.
Short Title:The Auk
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith