Genealogy of the nuclear β-fibrinogen intron 7 in Lissotriton boscai (Caudata, Salamandridae): concordance with mtDNA and implications for phylogeography and speciation

The power of phylogeographic inference resides in its ability to integrate information from multiple sources in an iterative hypothesis-testing framework. In this paper, we build upon previous mtDNA-based hypotheses about the evolutionary history of the Iberian newt Lissotriton boscai using sequences of the highly variable nuclear β-fibrinogen intron 7. In addition to the nuclear sequences, we produced new mtDNA data across the species range to delineate contact zones and test the congruence between nuclear and mitochondrial datasets at the same level of spatial organization. Through a combination of phylogenetic, phylogeographic continuous diffusion, and genetic landscape modelling analyses, we infer the evolutionary history of the species. We found notable congruence between nuclear and mtDNA datasets, which confirms deep and consistent differentiation between two major lineages that originated in the Miocene. Additionally, we found a new nuclear haplogroup with no mtDNA counterpart, roughly circumscribed to the Iberian Sistema Central mountains, and extensive areas of nuclear admixture across mtDNA lineages. We describe potential historical dispersal routes from an ancestral hypothetical refugium in the western end of the Sistema Central in central Portugal and highlight how deep phylogeographic breaks do not necessarily indicate cryptic speciation events