The taxonomy, phylogeny and biogeography of the New Zealand Thomisidae (Arachnida: Araneae)

Abstract

The New Zealand Thomisidae (crab spiders) are represented in New Zealand by two subfamilies (Stephanopinae and Thomisinae) and were used as a model group to test two competing theories on the origins of the New Zealand spider fauna. The New Zealand thomisids are also given their first full taxonomic revision. The two origin models essentially represent species radiations following recent dispersal or ancient vicariance events. Modern distribution data suggested that the stephanopines are poor dispersers and may provide evidence demonstrating a long period of separation from Australia; while in contrast, thomisines are known to be excellent dispersers. Maximum Likelihood and Bayesian analyses of cytochrome c suboxidase subunit I (COI), 28S ribosomal RNA (28S), histone H3 (H3), NADH dehyrogenase 1 (ND1) data and a combined genetic dataset was undertaken. Results indicate New Zealand stephanopines and thomisines form distinct endemic groups separate from sampled Australian species and appear to have separated from them around 5-6 million years ago. Additionally, genetic data from this study showed i) colour variations are not indicative of cryptic species; ii) previously described species are genetically distinct; iii) several suspected new species are also genetically distinct; iv) the relatively recent establishment of two Australian stephanopines and the occurrence of similar COI haplotypes in disjunct locations suggest that the dispersal ability of stephanopines is greater than previously thought and that radiation following colonization from Australia is a plausible explanation for the current diversity of the New Zealand thomisid biota. The taxonomic revision raises the number of described species from eight to eleven based on a combination of morphological and genetic data. In the stephanopines, Bryantymella Gen. nov. is erected to contain the type species Bryantymella angularis (Urquhart, 1885) comb. nov. as well as B. angulata (Urquhart, 1885) comb. nov., B. thorini sp. nov. and B. brevirostris sp. nov. Two Australian species, Sidymella longipes (Koch, 1874) and S. trapezia (Koch, 1874), are also recorded for New Zealand. Sidymella benhami (Hogg, 1910) is considered to be a junior synonym of Bryantymella angulata (Urquhart, 1885). In the thomisines, all species are now included in the previously monotypic genus Cymbachina Bryant, 1933. The genus now encompasses the type species C. albobrunnea (Urquhart, 1893), C. ambara (Urquhart, 1885) comb. nov., C. albolimbata (L. Koch, 1893) comb. nov., C. sphaeroides (Urquhart, 1885) comb. nov. and D. urquharti sp. nov. Synema suteri Dahl, 1907 is regarded as a junior synonym of C. ambara (L. Koch 1893). All previously described species are redescribed to a modern standard and sexes for some species are described for the first time. Three new species are described. Photographs of adults and diagnostic genitalic characters are included, as are diagnostic keys and updated synonymic, geographic and biological information. Overall, this study indicates that New Zealand thomisids appear to have split from their Australian relatives some 5-6 million years ago and taken in concert with the recent establishment of two Australian stephanopine species, it appears that dispersal to New Zealand by Australian colonists and subsequent radiation into endemic New Zealand forms is a plausible explanation for the current state of the fauna. Genetic and morphological data are mutually supporting and in concert have helped inform the first taxonomic revision ever undertaken for this family in New Zealand.