The radiation of hydrobiid gastropods in New Zealand: A revision including the description of new species based on morphology and mtDNA sequence information

A revision of New Zealand hydrobiid gastropods resulted in the description of 46 new species out of a total of 64, which belong to 15 genera, nine of them new. This revision is based on morphological data as well as sequence information of two mtDNA fragments. The majority of species occur in seepages, springs and the ground‐water and many have very narrow ranges. The morphological diversification appears to be linked to these habitats. Their common feature is the absence of predators. The genetics of three morphologically distinct species found in springs and streamlets suggest they have only recently split from the common, widespread Potamopyrgus antipodarum. Predator pressure, on the other hand, may have stabilised shell shape of three genetically distinct but otherwise cryptic species of Potamopyrgus, which occur in rivers, lakes and estuaries. Many species occur sympatrically. In one case of sympatry P. antipodarum appeared to displace another, slightly smaller species into crevices and other microhabitats not accessible for the former. Phylogenetic relationships were reconstructed based on the concatenated mtDNA sequences using Bayesian analyses, maximum likelihood and minimum evolution (LogDet distances). The three reconstruction methods gave very similar results suggesting that heterogeneous base frequencies were not a confounding factor. Analyses of character evolution revealed convergence in the digestive system as well as in the female and male genitalia. Radular features suggested a relationship of New Caledonian and New Zealand hydrobiids.