Hybrid zones are the regions where different species meet, mate and produce offspring. In a study just published in the Biological Journal of the Linnean Society we explore nine Triturus hybrid zones (all but one existing in nature), using a large amount of genetic markers (forty allozymes and a mitochondrial gene) and a highly informative morphological character (the number of rib-bearing vertabrae), for a huge number of newts (well over 700). Hybrid zones are narrow and individuals show less hybridity than would be expected under random mating, which shows that the different species are genetically pretty isolated. The degree of genetic isolation increases with genetic divergence. We do find mitochondrial DNA in the ‘wrong’ species, which illustrates that individual genes can be exchanged between species that for the rest manage to remain distinct. The number of ribs is a good indicator of species identity. Although there is some variation within species, most of this occurs close to hybrid zones, suggesting hybridization is to blame here. This synthesis marks the end of an era in a way: a lot of the data was already collected decades ago. It is also a strong base for future research on the Triturus hybrid zones using the new Ion Torrent protocol.

Reference: Arntzen, J.W., Wielstra, B., Wallis, G.P. (2014). The modality of nine Triturus newt hybrid zones, assessed with nuclear, mitochondrial and morphological data. Biological Journal of the Linnaean Society 113(2): 604-622.

I conducted this work as a Newton International Fellow.