Preliminary analysis of a hybrid zone between two subspecies of Zootermopsis nevadensis

For species largely allopatric in distribution, zones of contact provide an opportunity for hybridization, testing grounds for species boundaries, and may result in the formation of a new species. Thus, hybrid zones have the potential to provide important insights into speciation. In this study, we performed a preliminary analysis of a hybrid zone between two subspecies of the dampwood termite, Zootermopsis nevadensis (Z. n. nuttingi and Z. n. nevadensis) near Bartle, CA, using 12 microsatellite loci and a mitochondrial gene. Fifty-seven colonies collected in 36 locations were analyzed. The analysis of genetic markers revealed a large hybrid zone approximately 104 km in width. Although stepped clines best explained the data, we are unable to rule out the existence of a mosaic hybrid zone. We inferred weak selection (s* < 0.05%) against hybrids, but the data also suggested the existence of a barrier to gene flow from Z. n. nevadensis to Z. n. nuttingi, but not in the other direction. Given the large zone of contact, extensive sampling is needed to obtain a more complete characterization of the hybrid zone. However, the results of this study suggest that despite the accumulation of phenotypic and genetic differences and time since divergence (~2 million years), Z. n. nuttingi and Z. n. nevadensis are capable of extensive hybridization.