title: Quantifying the spatiotemporal dynamics in a chorus frog (Pseudacris) hybrid zone over 30 years.
abstract: Although theory suggests that hybrid zones can move or change structure over time, studies supported by direct empirical evidence for these changes are relatively limited. We present a spatiotemporal genetic study of a hybrid zone between Pseudacris nigrita and P. fouquettei across the Pearl River between Louisiana and Mississippi. This hybrid zone was initially characterized in 1980 as a narrow and steep "tension zone," in which hybrid populations were inferior to parentals and were maintained through a balance between selection and dispersal. We reanalyzed historical tissue samples and compared them to samples of recently collected individuals using microsatellites. Clinal analyses indicate that the cline has not shifted in roughly 30 years but has widened significantly. Anthropogenic and natural changes may have affected selective pressure or dispersal, and our results suggest that the zone may no longer best be described as a tension zone. To the best of our knowledge, this study provides the first evidence of significant widening of a hybrid cline but stasis of its center. Continued empirical study of dynamic hybrid zones will provide insight into the forces shaping their structure and the evolutionary potential they possess for the elimination or generation of species.
authors.affiliation: Department of Biological Science Florida State University 319 Stadium Drive Tallahassee Florida 32306.
authors.forename: Kristin N
authors.initials: KN
authors.lastname: Engebretsen
authors.affiliation: Department of Biological Science Florida State University 319 Stadium Drive Tallahassee Florida 32306.
authors.forename: Lisa N
authors.initials: LN
authors.lastname: Barrow
authors.affiliation: Department of Biological Sciences Museum of Natural Science Louisiana State University 202 Life Sciences Building Baton Rouge Louisiana 70803; Research School of Biology The Australian National University Gould Building 116 Canberra ACT 2601 Australia.
authors.forename: Eric N
authors.initials: EN
authors.lastname: Rittmeyer
authors.affiliation: Department of Biological Sciences Museum of Natural Science Louisiana State University 202 Life Sciences Building Baton Rouge Louisiana 70803.
authors.forename: Jeremy M
authors.initials: JM
authors.lastname: Brown
authors.affiliation: Department of Biological Science Florida State University 319 Stadium Drive Tallahassee Florida 32306.
authors.forename: Emily
authors.initials: E
authors.lastname: Moriarty Lemmon
keywords: Allozyme; Pearl River; hybrid cline; hybridization; microsatellite