Systematics of Ameiurus nebulosus (brown bullhead)
The brown bullhead, Ameiurus
nebulosus, is native to much of the eastern Atlantic coast, from Nova
Scotia to Florida and as far west as the Mississippi River. Within
its large range, the brown bullhead displays a considerable amount of morphological
variation, including colouration, vertebral numbers, and number of pectoral
rays. These differences have lead to a debate over the taxonomic
classification of the brown bullhead, which has been informally divided
into two subspecies,
Ameiurus nebulosus nebulosus in the north and
Ameiurus
nebulosus marmoratus in the south. The northern form is based on LeSureur's
1819 description of a specimen collected from the Delaware River in Pennsylvania.
In 1955 Hollbrook described another specimen from the Altamaha River in
Georgia, which he called Pimelodus marmaratus. These two descriptions
are the basis for the northern and southern and southern subspecies.
The systematic status of these two subspecies has remained problematic
to scientists and is in need of revision. Specimens have been abtained
from the U.S. National Museum of Natural History, University of North Carolina-Wilmington,
and Auburn University in an attempt to resolve this problem. It is
possible that the extreme morphological differences amongst the northern
and southern brown bullheads are due entirely to clinal geographic variation.
Undergraduate students involved with this project:
Erin D. Casey (1999-2000) gave presentation at Virginia Academy of
Science Annual Meeting, Radofrd Univ, Radford, VA, May 2000. Will
begin grad school at Eastern Illinois Univ., Dept of Biological Sciences,
in Fall 2000.