3RAD datasets used for phylogenomic, species delimitation, biogeography, and introgression analyses on Dugesia from Corsica and Sardinia

Speciation is a complex process where many evolutionary forces interplay.
The Mediterranean is acknowledged as one of the most relevant biodiverse
areas in the Palearctic region and researchers have long studied the
species inhabiting it to pursue the goals of evolutionary biology. Here,
we study a complex of freshwater flatworm species of the genus Dugesia
from Corsica and Sardinia using restriction site-associated DNA sequencing
(specifically, 3RAD) data to unravel their evolutionary history and tackle
the processes driving it. We assess the phylogenetic relationships and
population structure within the group and evaluate new species boundaries
using multispecies coalescent approaches. Furthermore, we offer insights
into the environmental niche model of the group and use said model to
guide our sampling efforts and collect and present molecular evidence for
the first time of Dugesia leporii specimens, endemic from Sardinia last
spotted in 1999. Our results indicate that paleoclimatic conditions rather
than microplate tectonic dynamics were likely an important driver of
diversification for the Corso-Sardinian group. Furthermore, our results
warrant the taxonomic re-evaluation of the group as eight primary species
candidates are established based on molecular data. Our study also reveals
the first case of interspecific natural hybridization reported in
Dugesiidae and, to our knowledge, in Tricladida. Finally, we discuss how
this hybridization might constitute a new form of hybrid speciation.