Revision and phylogenetic analysis of the North American species of Telorchis Luehe, 1899 (Cercomeria: Trematoda: Digenea: Telorchiidae)

Abstract

Telorchiids are plagiorchiform digeneans inhabiting the intestines of freshwater turtles, snakes, and salamanders. Previous systematic revisions of the group have been problematical because of a lack of information on intraspecific morphological variation. In the present study, examination of substantial numbers of specimens leads to the conclusion that 11 of the 31 nominal species of Telorchis reported from North America are valid. Numerical phylogenetic systematic analysis based on 18 homologous series and 30 total characters resulted in a single tree with a consistency index of 94%, due to two homoplasious characters. To maintain a classification consistent with the phylogenetic tree that is also most similar to previous nomenclature, only one of four previously proposed genera is recognized. The two relatively most plesiomorphic species are found in salamanders, whereas the rest inhabit amniotes (specifically turtles and snakes). Five of the nine species inhabiting amniotes appear to have co-speciated with their hosts. Two of the remaining four species appear to have evolved sympatrically via host switching from turtles to snakes. The remaining two species appear to have evolved sympatrically and without host switching, facilitated by mechanical premating isolation due to the appearance of an apomorphic genital pore position. Using the number of host species inhabited as an index of host specificity, it appears that the more recently evolved the species of Telorchis, the fewer hosts it inhabits.