A new phylogeographic perspective on a classical refugial area - colonization patterns and geneflow of spectacled salamanders (genus Salamandrina) in Italy
Final Report Abstract
We were able to generate a first thorough phylogeography of the genus Salamandrina, including the northern species, S. perspicillata, and the southern species, S. terdigitata, for which we analyzed over 700 individuals from 38 populations and used 3 types of molecular markers: one faster evolving mitochondrial gene (cyt b), two slowly evolving nuclear genes (POMC and RAG-1), as well as ten microsatellite loci (fast evolving). Prior to this study, no microsatellite loci had been isolated for this genus and neither had any nuclear gene sequences been studied. In addition, this study also included an unprecedented large number of populations and individuals, not only for this genus, but also in comparison with all other phylogeographic studies on endemic Italian vertebrates. While the mitochondrial marker confirmed previous findings, that divergence between the species is substantial, the nuclear gene sequences provided a surprising result: sequence divergence between the species is unexpectedly small. In fact, we even discovered allele sharing in one of the markers. Previous studies had dated the time of divergence of the two species between 7–10 mya. Using state-of-the-art coalescence methods on our multilocus dataset, we calculated a much more recent divergence event that took place only 120 ka. This finding completely changes the view of the history of this genus: the species split now is estimated to have taken place during the Eemian interglacial period, rather than during the Pliocene. Compared with estimates between northern and southern lineages of other vertebrate taxa with similar distribution, it is now at the lower end of the range. It is likely that our results from Salamandrina will put some doubt on divergence time estimates between other lineages that have been based solely on mitochondrial markers. Within each species, mitochondrial and nuclear genes showed comparatively little divergence. Overall, genetic diversity was greater in the southern species, but not to the extent we had expected based on comparative studies on other endemic Italian taxa. In the northern species, the pattern indicated recent expansion, which fit with postglacial expansion and in the southern species the pattern reflected that of more stable and isolated populations. Furthermore, we were able to discern an area of the central Apennine that may have served of a refugium, holding comparatively more genetic diversity. The combined use of mitochondrial and nuclear markers allowed us to discover hybrid individuals in one of the populations. Prior to this study, it had not been known that these species hybridize. We also elucidated the fine scale population genetic structure of S. perspicillata of a well sampled area in the Lepini Mountains, and found a substantial amount of structure within this small geographic area that was largely influenced by the mountainous terrain.
Publications
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(2011 – online first Nov. 2011) First microsatellite loci for spectacled salamanders (Salamandrina perspicillata and S. terdigitata) endemic to the Apennine peninsula. Conservation Genetics Resources
Hauswaldt, J.S., Angelini, C., Polok, A., Steinfartz, S.
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(2011) Hybridization of two ancient salamander lineages: Molecular evidence for endemic spectacled salamanders on the Apennine peninsula. Journal of Zoology 284 (4): 248-256
Hauswaldt, J.S., Angelini, C., Pollok, A., Steinfartz, S.
