Characterising Mitochondrial Capture in an Iberian Shrew

Abstract

Mitochondrial introgression raises questions of biogeography and of the extent of reproductive isolation and natural selection. Previous phylogenetic work on the Sorex araneus complex revealed apparent mitonuclear discordance in Iberian shrews, indicating past hybridisation of Sorex granarius and the Carlit chromosomal race of S. araneus, enabling introgression of the S. araneus mitochondrial genome into S. granarius. To further study this, we genetically typed 61 Sorex araneus/coronatus/granarius from localities in Portugal, Spain, France, and Andorra at mitochondrial, autosomal, and sex-linked loci and combined our data with the previously published sequences. Our data are consistent with earlier data indicating that S. coronatus and S. granarius are the most closely related of the three species, confirming that S. granarius from the Central System mountain range in Spain captured the mitochondrial genome from a population of S. araneus. This mitochondrial capture event can be explained by invoking a biogeographical scenario whereby S. araneus was in contact with S. granarius during the Younger Dryas in central Iberia, despite the two species currently having disjunct distributions. We discuss whether selection favoured S. granarius with an introgressed mitochondrial genome. Our data also suggest recent hybridisation and introgression between S. coronatus and S. granarius, as well as between S. araneus and S. coronatus.

Discordant phylogenies in the Sorex araneus group (Soricidae, Mammalia): Footprints of past reticulations?

“…Moreover, the haplotypes of the Carlit race of S. araneus from the Pyrenees are placed as a sister group to S. granarius I as previously demonstrated by Yannic et al (2008). We confirm Kunerth et al (2022) finding that there is another haplogroup ( S. granarius II) completely distinct from S. araneus . In our mitochondrial phylogeny, this is placed sister to S. coronatus .…”

“…The cyt b phylogenetic tree (Figure 2) is consistent with earlier reconstructions (Fumagalli et al, 1996(Fumagalli et al, , 1999Mackiewicz et al, 2017;Taberlet et al, 1994;Yannic et al, 2008Yannic et al, , 2010. As recently described in more detail by Kunerth et al (2022), S. granarius is represented by two unrelated haplogroups. Consistent with Kunerth et al, in our reconstruction, one of these (I) is placed as a close relative to S. araneus (chromosomal race Carlit), while the second (II) appears in a trichotomy with S. coronatus and S. araneus + antinorii clade (ML tree) or as a sister group to S. coronatus (Bayesian tree).…”

“…Consistent with Kunerth et al, in our reconstruction, one of these (I) is placed as a close relative to S. araneus (chromosomal race Carlit), while the second (II) appears in a trichotomy with S. coronatus and S. araneus + antinorii clade (ML tree) or as a sister group to S. coronatus (Bayesian tree). In Kunerth et al (2022) analysis, the second haplogroup of S. granarius also showed differing positions according to the two phylogenetic treatments used, but was not close to S. araneus in either case.…”

“…Several previous studies attempted to reconstruct phylogenetic relationships within the Sorex araneus group or parts of it using datasets of four to six nuclear markers (Bannikova et al, 2018;Kunerth et al, 2022;Yannic et al, 2008Yannic et al, , 2010. None of these studies produced a well resolved phylogeny.…”

“…Voucher specimens are deposited in the Zoological Museum of Lomonosov Moscow State University (ZMMU). Tissues of the western European species were kindly provided by colleagues (see Acknowledgements) or from specimens collected for the studies described in Yannic et al (2012) and Kunerth et al (2022).…”