Tryella species

Moulds, M. S., 2003, An Appraisal of the Cicadas of the Genus Abricta Stål and Allied Genera (Hemiptera: Auchenorrhyncha: Cicadidae), Records of the Australian Museum 55, pp. 245-304 : 255-256

Tryella species

Electrophoretic analyses grouped populations of Tryella species in a way that was consistent with different male genitalic morphologies (Serkowski & Moulds, unpub. data). Colour, colour pattern and size were not always consistent within these species groupings suggesting that these features are not necessarily reliable indicators of species limits. Male genitalic morphologies did, however, correlate with differences in wing and body morphologies (apart from size) where differences could be discerned. Thus, differences in male genitalic morphology have been given considerable emphasis in delineating Tryella species. While the converse is not necessarily true, i.e. individuals with identical male genitalia may not be conspecific, there was no evidence from either electrophoretic data or song analyses (Moulds, unpub. data) suggesting that this might be so.

Biogeography

Distribution of Abricta and allied genera. The six genera of the Abricta complex fall into distinct geographic regions. Abricta sensu str. and Monomatapa are strictly Afrotropical in distribution. Abroma has an Afrotropical type species but is otherwise widely distributed through Mauritius, Madagascar, Sri Lanka, and possibly India, and doubtfully through southeast Asia, and even South America; special caution should be exercised in including those species of non-Afrotropical origin in Abroma as none have been adequately described and further examination is likely to show that some at least do not belong to Abroma .

Aleeta and Tryella are restricted to Australasia. The sole representative of Aleeta , A. curvicosta , is endemic to eastern Australia. The 14 known Tryella species are also endemic to Australia, except for T. lachlani that marginally extends its distribution to the southwest coast of Papua New Guinea. Only two Tryella species have distributions that partly impinge on that of Aleeta . The distribution of Chrysolasia remains uncertain.

Distribution of Tryella species ( Fig. 30). Tryella species occur primarily across the northern half of Australia with just two extending south of 30°S latitude. Most have extensive distributions spanning at least 500 km. The apparent absence of Tryella species from Arnhem Land and the Tanami Desert regions of the Northern Territory, and the Kimberley and Pilbara regions of Western Australia is most likely a consequence of insufficient collecting.

The occidens species group, comprising occidens, stalkeri, noctua , infuscata , ochra and lachlani , has a distribution that extends from Western Australia northeastwards to Cape York Peninsula. There is a direct correlation between the distribution of these species and their phylogenetic positions from the cladistic analyses ( Fig. 17), with the most ancestral species occurring in the far west of Western Australia and the most derived in the north of Cape York Peninsula. The disjunct distributions of the three Western Australian species suggest that they were once far more widespread and have contracted their ranges with changing habitat.

The adela species group comprising adela , burnsi , kauma , graminea and willsi , and the possibly allied species castanea and crassa , is widespread across the monsoonal north of Western Australia, the Northern Territory and Queensland; only graminea and willsi extend their ranges beyond the monsoonal north to reach the drier interior of the northeast quarter of Australia.

The sister group relationship of rubra with the adela species group and its allies castanea and crassa also reflects a western (or northwestern) origin for Tryella . The distribution of rubra is consolidated across the western limits of the adela species group, that is, across the distributions of castanea , crassa and adela . These three species could be interpreted as the three basal taxa of the adela species group clade. This distribution pattern supports the hypothesis that the origin of the adela group was also somewhere in the west or north-west of the continent and radiated eastward into Queensland, rather than at the base of the Gulf of Carpentaria where the current concentration of species is found. The concentration of species at the base of the Gulf of Carpentaria could be a consequence of the eastward radiations of the occidens species group and adela species group converging.