On the classification, evolution and biogeography of terrestrial haemadipsoid leeches (Hirudinida: Arhynchobdellida: Hirudiniformes)

A scourge of tropical and subtropical jungles, bloodfeeding terrestrial leeches of Haemadipsidae have long confused systematists and defied sensible biogeographic interpretation. The family Haemadipsidae usually includes problematic taxa that neither fit the typical IndoPacific distribution of the group, nor properly match diagnostic characters used to define the family. Historically, four additional families—Xerobdellidae, Diestecostomatidae Mesobdellidae and Nesophilaemonidae—have occasionally been recognized for New World and European representatives, though agreement on the composition of those families has not been consistent. Here, we expand the phylogenetic sampling of non-IndoPacific (among other) genera to include Meso American Diestecostoma species and Nesophilaemon skottsbergii from the Juan Fernandez Archipelago in order to critically assess prior hypotheses in a molecular phylogenetic analysis of arhynchobdellid leeches. The result, based on nuclear 18S rDNA and 28S rDNA and mitochondrial COI indicates that there are two distantly related lineages of bloodfeeding terrestrial leeches. The otherwise monophyletic family Haemadipsidae is found to exclude species of Xerobdella, Mesobdella and Diestecostoma. Xerobdellidae is formally resurrected to accommodate species of those three genera. Morphological characteristics corroborate the distinction of Haemadipsidae and Xerobdellidae on the basis of sexual and nephridial characters. Idiobdella seychellensis belongs in Haemadipsidae notwithstanding its lacking respiratory auricles. Nesophilaemon skottsbergii too is in Haemadipsidae notwithstanding its geographic proximity to the xerobdellid Mesobdella gemmata. The characters used to define haemadipsoid families are reevaluated. Feeding preferences and biogeographic patterns are also examined.