Rapid radiation and hybridization contribute to weak differentiation and hinder phylogenetic inferences in the New World Mallard complex (Anasspp.)

Abstract

ABSTRACT Of the 13 taxa composing the Mallard complex, 4 occur in North America: the sexually monochromatic American Black Duck (A. rubripes), Mexican Duck (A. [platyrhynchos] diazi), and Mottled Duck (A. fulvigula), and the dichromatic Mallard (Anas platyrhynchos). Although morphologically distinct, inferring the evolutionary relationships of this group is confounded by extensive genic sharing due to incomplete lineage sorting and ongoing hybridization. The objective of this study was to examine the underlying cause (i.e. incomplete lineage sorting vs. contemporary gene flow) of phylogenetic uncertainty. Whereas most taxa were fairly structured at mitochondrial DNA, a “starburst” pattern of divergence consistent with a rapid radiation was recovered with 17 nuclear introns. Furthermore, nuclear-based divergence estimates and tests of population structure recovered Florida and West Gulf Coast Mottled Ducks as well-differentiated and genetically diagnosable from each other and the remaining taxa, whereas Ma...