Ethiopian rats (genus Stenocephalemys) represent a monophyletic group of Ethiopian endemic rodents that diverged in the Ethiopian Highlands during the Pleistocene. Because of the frequent occurrence of so-called reticulate evolution (i.e. repeated hybridization of partially diverged populations), their taxonomy has not been adequately resolved, despite the fact that they belong to the most abundant rodent genus in Ethiopia and are important as pests and carriers of pathogens (e.g. hantaviruses). Here we analysed material for 623 Stenocephalemys specimens using integrative taxonomy composed of genomic analyses (388 nuclear markers and complete mitogenomes), 2D-geometric morphometry of skulls and classical morphometry of external traits. The genus consists of six clearly defined gene pools (= species), characterized by specific morphology, ecology and distribution. Two of them, described here as new species, live in fragmented populations in Afroalpine habitats in the north-western part of the Ethiopian Highlands. We also showed that mitochondrial DNA is not applicable as a universal diagnostic tool for species discrimination in Stenocephalemys, because of multiple cases of mitochondrial introgression. This finding illustrates the utility of the genus as a suitable model for future studies of mito-nuclear coevolution along an elevational gradient.
Non-native species are known to escape their parasites following introduction into a new range, but they also often acquire local parasites as a function of time since establishment. We compared the parasite faunas of five non-native Ponto-Caspian gobies (Gobiidae) and local fish species (Perca fluviatilis, Gymnocephalus cernua, Gobio gobio) in three European river systems; the Rivers Rhine, Vistula and Morava, where Ponto-Caspian gobies were introduced 4-13 years prior to the study. Overall parasite species richness was considerably lower in non-native gobies compared to local fish species, and the same result was found at the component and infra-community levels. Both parasite abundance and diversity greatly varied among the regions, with the highest values found in the River Vistula (Wloclawski Reservoir), compared to a relatively impoverished parasite fauna in the River Morava (Danube basin). While only half of parasite species found in local hosts were acquired by non-native gobies, most of the parasites found in gobies were shared with local fish species related either phylogenetically (percids) or ecologically (benthic gudgeon), including the co-introduced monogenean Gyrodactylus proterorhini. As a result, similarity in parasite communities strongly reflected regional affiliation, while phylogenetic distances between fish host species did not play a significant role in parasite community composition. In accordance with other studies, all parasites acquired by gobies in their new range were generalists, all of them infecting fish at the larval/subadult stage, indicating the possible importance of gobies in the life cycle of euryxenous parasites. The absence of adult generalists, particularly ectoparasites with low host specificity, in non-native fish may reflect their generally low abundance in the environment, while an absence of adult endoparasitic generalists was probably related to other factors.