Third genus of Parastenocaridid Copepods from Australia supported by molecular evidence (Copepoda, Harpacticoida)

Abstract

A new species of parastenocaridid copepods was discovered in aridWestern Australia, which could not be assigned to any of the currently known genera. Molecular evidence reveals only a remote phylogenetic relationship with two other Australian genera, Parastenocaris Kessler, 1913 and Kinnecaris Jakobi, 1972, and the pairwise distances among them are remarkably similar to those among three canthocamptid genera used as outgroups in our analysis. We interpret this as a very strong molecular signal in support of establishing a new genus for this Australian parastenocaridid, in addition to many morphological characters. The genus Dussartstenocaris n. gen. is currently monospecific, although we notice some morphological similarities between Dussartstenocaris idioxenos n. sp. and the Portuguese Parastenocaris conimbrigensis Noodt & Galhano, 1969. The two differ by the shape of the third leg exopod in male, a bifid exopodal spine being an autapomorphic feature of the new genus. The fifth legs both in male and female are an additional morphological character (or set of characters) that distinguish Dussartstenocaris from all 258 parastenocaridid species. The new genus differs from the other two Australian genera by at least ten major morphological characters each, seven of which are probably apomorphic features. This interesting parastenocaridid comes from a newly discovered locality in the Yilgarn region, with an unprecedented diversity of copepod crustaceans (up to seven species per single bore, and 22 morpho-species in total). This equals to 70% of the previously recorded diversity in the whole region, although the area investigated represents less than 3% of its surface. We also report on the first ever case of two sympatric parastenocaridids in Australia, which are a rare group on this continent. A very strong seasonal dynamics in this subterranean community was observed, and this is a novel concept for these ecosystems globally. A key to Australian species of Parastenocarididae Chappuis, 1940 is also included.