Species status and conservation issues of New Zealand’s endemic Latrodectus spider species (Araneae : Theridiidae)

New Zealand has two endemic widow spiders, Latrodectus katipoPowell, 1871 and L. atritusUrquhart, 1890. Both species face many conservation threats and are actively managed. The species status of the Latrodectus spiders of New Zealand was assessed using molecular (COI, ITS1, ITS2) and morphological methods and with cross-breeding experiments. Latrodectus katipo and L. atritus were not found to be reciprocally monophyletic for any of the gene regions or morphological traits. Other than colour, which is variable, there were no morphological characters that separated the two species, which cross-bred in the laboratory and produced fertile eggsacs. Colour variation is clinal over latitude and correlates significantly with mean annual temperature. We conclude that L. atritus is a junior synonym of L. katipo. An example of introgression from the Australian species L. hasseltiiThorell, 1870 was also detected and its conservation implications are discussed.