Genetic Divergence Across Glacial Refugia Despite Interglacial Gene Flow in a Crested Newt

Abstract

MtDNA-based phylogeography has illuminated the impact of the Pleistocene Ice Age on species distribution dynamics and the build-up of genetic divergence. The well-known shortcomings of mtDNA in biogeographical inference can be compensated by integrating multilocus data and species distribution modelling into phylogeography. We re-visit the phylogeography of the Italian crested newt (Triturus carnifex), a species distributed in two of Europe’s main glacial refugia, the Balkan and Italian Peninsulas. While a new 51 nuclear DNA marker dataset supports the existence of three lineages previously suggested by mtDNA (Balkan, northern Italy and southern Italy), the nuclear DNA dataset also provides improved resolution where these lineages have obtained secondary contact. We observe geographically restricted admixture at the contact between the Balkan and northern Italy gene pools and identify a potential mtDNA ghost lineage here. At the contact between the northern and southern Italy gene pools we find admixture over a broader area, as well as asymmetric mtDNA introgression. Our species distribution model is in agreement with a distribution restricted to distinct refugia during Pleistocene glacial cycles and postglacial expansion with secondary contact. Our study supports: (1) the relevance of the north-western Balkan Peninsula as a discrete glacial refugium; (2) the importance of north-eastern Italy and the northern Apennine as suture zones; and (3) the applicability of a refugia-within-refugia scenario within the Italian Peninsula.

Whole‐genome analysis of multiple wood ant population pairs supports similar speciation histories, but different degrees of gene flow, across their European ranges

“…Opportunities for, for example, gene flow may vary in both time and space, introducing variation in estimates of migration rates. For example, if two species would have utilized multiple glacial refugia throughout their ranges, in which opportunities for gene flow within and between the species were not homogeneous, it could introduce variation in the estimates of, for example, past gene flow (e.g., Schuler et al, 2019; Wielstra et al, 2021). Further, should the populations of one or both of the species be in contact with a third in a certain portion of their ranges, then they may inadequately represent the history of their species (e.g., Rautsaw et al, 2020).…”

Piecing the barcoding puzzle of Palearctic water frogs (Pelophylax) sheds light on amphibian biogeography and global invasions

“…or informing on previous vicariance events that only left trace in the mitochondrion (ghost lineages, e.g., Wielstra et al, 2021) due to subsequent lineage fusion (Garrick et al, 2019).…”

Recurrent hybridization and gene flow shaped Norway and Siberian spruce evolutionary history over multiple glacial cycles

“…Both animal and plant species went through cycles of contractions and expansions as a result of glacial cycles (Fletcher et al 2010; Nevado et al 2018; Shuvaev et al 2023). These cycles were generally accompanied by sequences of reproductive isolation and strong genetic divergence during contraction phases and to secondary contact(s) and genetic admixture during expansion phases (Nevado et al 2018; Wielstra, Salvi, and Canestrelli 2021; Zemlak et al 2008). This played a major role in shaping the distribution of genetic variation of closely related boreal species.…”