A new species of Haemopis (Annelida: Hirudinea): evolution of North American terrestrial leeches.

Among the relatively few terrestrial leeches known worldwide, only two (Haemopis terrestris, Haemopis septagon) are described from North America. Here we report a third terrestrial leech collected from the southern part of New Jersey, USA. Tissue samples were obtained from 14 individuals representing three populations, and morphological characters were scored after dorsal and ventral dissections. Maximum Parsimony and Bayesian Inference analyses resolved phylogenetic relationships within the genus Haemopis using cytochrome c oxidase subunit 1 (CO1), 12S ribosomal RNA (rRNA), and 28S rRNA gene fragments, establishing the monophyly of North American haemopids and terrestrialism as a synapomorphy for some members of the group. Morphological distinctions and geographic isolation support the designation of a new species of terrestrial leech, Haemopis ottorum. Phylogeographic interpretations of the haemopid clade suggest that terrestrialism was derived from a northern, aquatic ancestor whose descendents were initially confined to Midwestern States and central Canada by the Appalachian Range. More recently, the terrestrial lineage (i.e., Haemopis terrestris) diverged near the southern extent of its range and began a northeasterly migration along coastal states giving rise to Haemopis septagon and Haemopis ottorum, the latter of which appears to define the leading edge of a northward expansion.