Riethia Kieffer, a genus of the non-biting midge subfamily Chironominae (Diptera: Chironomidae) is distributed in Australia, New Zealand, New Caledonia and South America. This austral distribution could be due to earth history (vicariance) or from Southern Hemisphere dispersal(s). We obtained samples from each area, most intensively from throughout Australia. We included putative sister genus Pseudochironomus Malloch, many genera from tribe Tanytarsini, enigmatic taxa in Chironomini and conventional outgroups from other subfamilies. We assembled a multilocus molecular dataset for four genetic regions from 107 individuals to reconstruct the first dated molecular phylogeny for the group. Four terminal clusters corresponded to unreared (thus unassociated) larvae. Monophyly was supported for ‘core’ Riethia, Pseudochironomus, putative tribe Pseudochironomini, tribe Tanytarsini (including enigmatic Nandeva Wiedenbrug, Reiss & Fittkau) and subfamily Chironominae. All species are monophyletic except for R. cinctipes Freeman, which includes R. neocaledonica Cranston. Riethia zeylandica Freeman, previously thought to be widespread in eastern Australia, now is a New Zealand endemic with Australian specimens allocated now to several regionally restricted species. The origin of Riethia was at 60.6 Ma (‘core’) or 52.1 Ma depending on the relationship of two South American species. Both dates are before the break-up of South America and Australia. Diversification within crown group Riethia started before the Cretaceous–Paleogene boundary, with subsequent separation at 52 Ma of an Australian ‘clade I’ from its sister ‘clade II’, which comprises Australian, New Zealand and New Caledonian species. Inferred dates for species origins of New Caledonia and New Zealand taxa imply transoceanic dispersals from eastern Australia. Western Australian species diverged during the mid to late Miocene from their eastern Australian sister taxa. This correlates with the onset of drying of Australia and the separation of mesic east from west by the formation of an arid proto-Nullarbor. Taken together, the inferred tempo of diversification in the group included both older ages reflecting earth history, yet with suggested recent intra-Pacific separations due to transoceanic dispersals.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.
Vol. 34 • No. 3