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Morphological adaptation with no mitochondrial DNA differentiation in the coastal plain swamp sparrow

Auk

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Abstract

We estimated genetic differentiation between morphologically distinct tidal marsh populations of Swamp Sparrows (Melospiza georgiana nigrescens) and the more wide-spread 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/tlys/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.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Morphological adaptation with no mitochondrial DNA differentiation in the coastal plain swamp sparrow
Series title:
Auk
Volume
115
Issue:
3
Year Published:
1998
Language:
English
Contributing office(s):
Patuxent Wildlife Research Center
Description:
706-712
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Auk
First page:
706
Last page:
712
Number of Pages:
7