Fantastic beasts and how to delimit them: an integrative approach using multispecies coalescent methods reveals two new, endemic Dugesia species (Platyhelminthes: Tricladida) from Corsica and Sardinia

Dugesia hepta and D. benazzii are two species found in Sardinia and Corsica. Previous studies have been unable to resolve their evolutionary relationships and there was doubt about the monophyly of D. benazzii. This study used molecular and morphological data to develop a rigorous species-delimitation procedure within an integrative framework. Three different species discovery methods (ABGD, GMYC, and mPTP) were applied on single-locus data to formulate primary species hypotheses. Secondary species hypotheses were proposed based on two Bayesian species-validation methods (BPP and BFD), morphological, and karyological traits. This study presents evidence supporting the recognition of two new species: Dugesia mariae from Corsica and Dugesia hoidi from Sardinia. A redescription of D. benazzii is also reported. The phylogenetic relationships between these four species were resolved with high support, except for D. hoidi. The performance of the different molecular-delimitation methodologies is discussed, as well as the presence of ciliate parasites in D. benazzii and D. mariae.

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