02334nas a2200205   4500008004100000245017300041210006900214300001200283490000700295520162800302653001701930653002401947653001401971653001501985653001302000100001602013700001802029700001902047856006202066       2018                        eng d00aDiversification and biogeographic history of the Western Palearctic freshwater flatworm genus Schmidtea (Tricladida: Dugesiidae), with a redescription of Schmidtea nova0 aDiversification and biogeographic history of the Western Palearc  a335-3510 v563 aAbstract The freshwater flatworm genus Schmidtea is endemic in the Western Palearctic region, where it is represented by only four species, thus contrasting with the high species diversity of the closely related genus Dugesia within Europe. Although containing an important model species in developmental and regeneration research, viz. Schmidtea mediterranea, no evolutionary studies on the genus Schmidtea have been undertaken. For the first time, we present a well-resolved molecular phylogenetic tree of the four species of the genus, inferred on the basis of two molecular markers, and provide also the first detailed morphological account of Schmidtea nova. The phylogenetic tree generated corroborates an earlier speciation hypothesis based on karyological data and points to chromosomal rearrangements as the main drivers of speciation in this genus. The high genetic divergence between the four species, in combination with previous dating studies and their current geographic distribution, suggests that Schmidtea could have originated in Laurasia but lost most of its diversity during the Oligocene. Thus, its present distribution pattern may be the result of the expansion of three of its four relictual species over Europe, probably after the Pleistocene glaciations. Our detailed morphological study of S. nova revealed that it shows a number of remarkable features: interconnected testis follicles, parovaria, an ejaculatory duct exiting into the primary as well as the secondary seminal vesicle by means of a nipple, and the wall of the distal section of the ejaculatory duct being sclerotic or chitinized.10aBiogeography10amolecular phylogeny10aSchmidtea10aspeciation10ataxonomy1 aLeria, Laia1 aSluys, Ronald1 aRiutort, Marta  uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/jzs.12214