Mitochondrial DNA sequence revealed contrasting demographic history between the black bullhead (Ameiurus melas) and its cryptic lineage in North America

Department of Biological Science, University of Tulsa, 800 S. Tucker Drive, Oklahoma - 74104, USA

^a Corresponding author: aup17@psu.edu

Received: 21 July 2010
Accepted: 17 November 2010

Abstract

The black bullhead, Ameiurus melas of the family Ictaluridae, is a freshwater fish native to North America that was introduced throughout Europe in the late 1800s. Using mitochondrial DNA (mtDNA) as a genetic marker, the present study investigates the genetic structure and historical demography of A. melas in North America. MtDNA-based phylogenetic analyses revealed the existence of two distinct lineages (A and B) of A. melas. While lineage A clustered with the previously reported sequences of A. melas, lineage B emerged as a unique clade like other species of the genus Ameiurus. Individuals belonging to lineage B were mostly from the south central region of the United States, the region that never glaciated during the last Ice Age. Results of a fossil-based molecular clock analysis suggest that lineage A and the paraphyletic lineage B of A. melas diverged from their respective common ancestors approximately 3 (±0.2) and 15.9 (±1.3) million years ago. Lineage B could possibly be a hybrid species, possessing the mtDNA haplotype of its maternal parent, an Ameiurus species that has gone extinct. While lineage A showed evidence of population expansion, lineage B did not show any evidence of population expansion, but rather is comprised of geographically structured populations.