Wednesday, December 12, 2001 - 10:00 AM
0713

The enigmatic Telmatogetoninae - some new information on the basal chironomid midges

Peter S Cranston, Department of Entomology, University of California, Davis, Department of Entomology, One Shields Avenue, Davis, CA

Early ideas on the marine midges (family Chironomidae) implied monophyly - in a subfamily Clunioninae or tribe Clunionini of the subfamily Orthocladiinae. This grouping comprised taxa centred on Clunio - small midges of intertidal shores, rockpools and reefs, and genera such as Telmatogeton and Thalassomya, larger taxa of wave-swept coastal rocks, or montane Hawai'ian streams. In reality all that the two groupings had in common was their marine habitat, and some reductional features of the body. As early as 1960, Strenzke, using Hennig's approach to determination of relationships, assessed the Clunio grouping to be sister to a clade of orthoclads with terrestrial larvae. However Strenzke was less certain about Telmatogeton and allies, but recognizing it as plesiomorphic, and unrelated to Clunio and he dismembered the polyphyletic Clunioninae. This action has been accepted ever since.

The subsequent history of Telmatogeton and allies has been controversial. Brundin (1966) claimed a relationship to the Diamesinae, although he acknowledged all shared states appeared to be plesiomorphies, and distinctive features were all highly autapomorphic. In a comprehensive survey of female genitalia of Chironomidae, Sæther (1977) suggested that on these features alone, the taxon deserved family rank as sister to the remaining Chironomidae. In a critique of Saether's use of symplesiomorphies, autapomorphies and non-parsimonious reasoning, Ashe, Murray and Rice (1987) disputed this, adding that a marine ancestor for the Chironomidae radiation was prima facie unlikely.

A pilot study by the author and Lyn Cook (Australian National University) undertaken to assess the utility of DNA sequence information has shown ease of extraction and sequencing with traditional primers. Lacking any funding specifically dedicated to this project, only 40 taxa have been sequenced for either or both 16S and COII genes. The former proved informative, the latter tending to saturation at the level of subfamily and tribe. Early results show a wealth of informative sites and allow construction of trees in which certain nodes appear robust. These analyses, even though based on under-sampling, show agreement with some hypotheses of high level relationship, notably in finding the subfamily Telmatogetoninae to be sister to the remaining Chironomidae.

The implication that this phylogenetic position confirms an ancestral marine ancestor for the Chironomidae does not follow necessarily. Basal taxa in the sister group the Leptoconopinae of the Ceratopogonidae include those whose larvae live in moist soils in marine conditions, but also in similar freshwater habitats. Plesiotypic features of next clade in the Chironomidae phylogeny - Archaeochlus of the apparently paraphyletic subfamily Podonominae show retention of larval spiracles and adult female functional mandibles - and an ecology associated with thin water films on ancient exposed rocks with seasonal flow.



Species 1: Diptera Chironomidae (midge)
Keywords: Phylogeny

The ESA 2001 Annual Meeting - 2001: An Entomological Odyssey of ESA