The Chesapeake logperch, Percina bimaculata (Halderman) has a disjunct distribution when compared to other species in the subgenus Percina. Members of this subgenus in Pennsylvania include Percina caprodes caprodes (Rafinesque), Percina caprodes semifasciata (DeKay), and P. bimaculata. Historically the Chesapeake logperch was known only from the Susquehanna River and Potomac River basins. Its range is now restricted to the Sus...

In colonial‐breeding species, prebreeders often emigrate temporarily from natal reproductive colonies then subsequently return for one or more years before producing young. Variation in attendance–nonattendance patterns can have implications for subsequent recruitment. We used open robust‐design multistate models and 28 years of encounter data for prebreeding female Weddell seals ( Leptonychotes weddellii [Lesson]) to evaluate...

The definition of the species category has stimulated more debate than perhaps any other topic in the biological sciences. There are currently more than 22 different species concepts and the debate continues on which concepts apply to all organisms, which concepts are operational and which concepts should be used in specific circumstances. The first major division of the types of concepts depends on whether one views species a...

More than 22 different species concepts have been proposed. The concepts in general reflect the philosophical outlook, particular expertise, and the groups on which the authors are working. The full‐length papers in this special issue dedicated to species concepts relative to fishes are based on presentations by the authors at the 2001 annual meeting of the American Society of Ichthyologists and Herpetologists at University Pa...

Historically, the cichlid fishes of Lake Malawi, which probably represent one of the best examples of rapid radiation of vertebrates, have been diagnosed with morphological and genetic data. Many of the populations once thought to be conspecific have been hypothesized to be separate species based on behavioural data. The use of behavioural data, as expressed in mate choice based on colour patterns or bower shapes, has been suc...