Data from: Rise and fall of a hybrid zone: implications for the roles of aggression, mate choice, and secondary succession

Hybridization can be an important evolutionary force by generating new
species and influencing evolution of parental species in multiple ways,
including introgression and the consequences of hybrid vigor. Determining
the ecological processes underlying evolution in hybrid zones is difficult
however because it requires examining changes in both genotypic
frequencies over time and corresponding ecological information, data that
are rarely collected together. Here, we describe genetic and ecological
aspects of a hybrid zone between the Eastern Fence Lizard, Sceloporus
undulatus, and the Florida Scrub Lizard, Sceloporus woodi, occurring over
at least 23 generations. The hybrid zone, discovered greater than 35 years
ago using morphological characters, originally consisted of nearly even
proportions of parental species and hybrids. Now, using genetic markers
(species-diagnostic mtDNA sites and 6 nDNA microsatellite loci across a
total of n = 117 individuals), we confirm not only that hybridization
occurred but also that subsequent backcrossing has resulted in highly
introgressed hybrids, with many hybrids containing mitochondrial DNA from
one species on a nuclear DNA background of the other. Ecological aspects
explaining these shifts in genetic composition include female mate choice,
changes in habitat associated with secondary succession, and, most
strongly, a hierarchy of male territorial advantage—ecological mechanisms
likely to be involved in the emergence and disappearance of many animal
hybrid zones. Our results suggest that genetic assimilation is not a
significant threat to either species and that rather transient hybrid
zones such as this may serve to increase genetic diversity and are
candidates for causing genetic discordance in phylogeographic analyses.