Diptera: Chironomidae)

Botryocladius gen. n.: a new transantarctic genus of orthocladiine midge (Diptera: Chironomidae) Peter S. Cranston1 and Donald H.D. Edward2 1CSIRO Entomology, G.P.O. Box 1700, Canberra, A.C.T. 2601, Australia. 2Department of Zoology, The University of Western Australia, Nedlands, Western Australia 6907 Abstract. A new genus of orthocladiine Chironomidae, Botryocladius (type species B. grapeth sp. n. from eastern Australia) is described and illustrated in all life history stages. All thirteen included species are described as new, six from eastern Australia (B. grapeth, B. brindabella, B. mdfrc, B. collessi, B. tasmania, B. australoalpinus), two from Western Australia (B. bibulmun and B. freemani), one from ephemeral streams on rock outcrops in western, central and eastern Australia (B. petrophilus) and four from Patagonian Argentina and Chile (B. edwardsi, B. glacialis, B. mapuche and B. tronador). All Australian species are known from at least pupal exuviae, most from adult males, and several from larvae. In contrast, only B. edwardsi amongst Neotropical species is known from the adult male: all others are described from pupal exuviae. The immature stages are lotic in Australian permanent and temporary streams and Patagonian glacial streams and rivers, and lentic in Neotropical glacial-fed and Australian subalpine lakes. Botryocladius appears to belong with a grouping centred on two formally undescribed taxa from Australia. The genus evidently demonstrates a vicariant distribution with at least two sister-group relationships between South American and Australian taxa, providing a minimum dating for the clade of 38 m.y.b.p., with apparent absence from New Zealand indicating a maximum date of 80 m.y.b.p.. Introduction The evidence for extant insect genera being shared between Australia have been examined and eliminated from widely separated Gondwanan land masses is accumulating, not consideration. least for the non-biting midges (Chironomidae) (e.g. Freeman, Finally we discuss the biology, biogeography and phylogeny. 1961; Brundin, 1966). However, the increasingly well- For the subfamily Orthocladiinae the phylogeny is so uncertain understood vicariant patterns shown by the chironomid faunas that Sæther (1990a) suggested that orthocladiine genera had of the southern continents have been recognised predominantly character distributions “in such a mess” as to render it from systematic studies concerning only three of the subfamilies impossible to find any pattern of relationships. In that study, a of Chironomidae, namely the Podonominae (Brundin, 1966; matrix was prepared (but unpublished) and analysed under Cranston, Edward & Colless, 1987; Cranston & Edward, 1998), several criteria, but the results were used more to discuss Aphroteniinae (Brundin, 1966; Cranston & Edward, 1992) and parsimony as an objective criterion for analysis than to assess the Diamesinae, tribe Heptagyiae (Brundin, 1966). In all these relationships of taxa (Sæther, 1990a). In the same conference examples, the biotically-related landmasses comprise Australia, proceedings, Rossaro (1990) showed the results of a numerical southern South America and southern Africa (for the latter area, study of Orthocladiinae relationships, again without publishing the presence of an undescribed taxon of Heptagyiae is newly a matrix. These two efforts attempted to estimate the phylogeny noted here), with a New Zealand connection in certain groups. of the complete subfamily, or at least those taxa known in all life In the more speciose and cosmopolitan subfamilies stages. Such a remit is beyond the present study, and we seek Orthocladiinae and Chironominae, such austral relationships have the sister group for Botryocladius and the likely relationship of been little explored: Edwards (1931) denied their existence, in the genus with “similar” taxa. contrast to Freeman’s (1961) recognition of Australian / Patagonian-South Chilean links amongst some “more primitive Methods, materials and phylogenetics or apparently more primitive genera” of Chironominae and Orthocladiinae. Long-term studies in Australia, and more A variety of collection methods have been used. Pupae and recent collections from southern South America have revealed a their exuviae were collected by exposing one or more drift nets diversity of austral vicariant taxa, including several genera of with a 300 µm mesh to intersect flowing water surfaces for up to Orthocladiinae going beyond the “primitive” Stictocladius 24 h.. The association between larva, pupa and adult necessary Edwards (Freeman, 1961; Edward, 1989). One such genus for full taxonomic descriptions has been attempted by rearing appears to be phylogenetically relatively derived within the live larvae individually through to the adult. Live larvae were Orthocladiinae, and undescribed despite being speciose, and placed individually in a few ml of native (or tap) water in widespread and abundant in lotic and lentic in systems in cotton-wool stoppered 50mm x 10mm glass vials, and Australia and Patagonia/Chile. maintained at cooler than ambient temperatures, without Here we describe this taxon from Australia, Argentina and aeration. Any emerged adults and associated exuviae were Chile, provide diagnoses based on all stages (adult males and preserved in 70% ethanol. If metamorphosis did not occur within females, pupae and larvae), key all species based on pupal about one week, raising the temperature by about 5°C exuviae and most Australian species from adult males and sometimes hastened the process. larvae. Taxa based on pupae alone, without associated adults, Microscope slide preparation involved clearing where might be suspect as potential junior synonyms of described, necessary with 10% KOH, neutralisation and initiation of unreared, adult-based taxa. To guard against this possibility all dehydration with glacial acetic acid, then mounting from previously described orthocladiine taxa from Patagonia and propan-2-ol (isopropanol) into Euparal. Exuviae were displayed by dissecting the cephalothorax from the abdomen, and attempts R., river; R, R1, R4+5, wing veins R, R1 and R4+5 respectively, were made to remove pharate adults from exuviae. setal count; RM, radius to media crossvein; RO, ring organ, Morphological terminology follows Sæther (1980) and distance from base; S, south; S.Ch., sensilla chaetica; Scts, Cranston (1994) except where Langton’s (1994) suggested use scutellum, setal count; S.F., state forest; St.IX, sternite IX, setal of taenia (adjective taeniate) for “filamentous” or “lamelliform” count; Sq, squama, setal count; S.V., ratio of Fe + Ti : Ta1; TIX, (LS) pupal setae is adopted. In addition, in pupal descriptions tergite IX. setal count; Ta 1-5, tarsomeres 1-5; temp., temporals, we refer to the conjunctive as if belonging to the segment setal count; th.h.l., thoracic horn length; Ti, tibia; U., upper; anterior to it, rather than the conventional but cumbersome vms.l., length of ventromental setae; V.R., ratio of length of Cu1 citation of the segment number that precedes and follows. : length of M; W, west; W.l., wing length (arculus to apex) in Many measurements of larvae and pupae are of exuviae but mm. larval length and head capsule measurements are based on complete fourth-instar larvae. Measurements of larval antennal Phylogenetics features and subsequent calculations of the antennal ratio are based on the sclerotised portions of the antenna, disregarding For phylogenetic analyses at generic level, taxa included the variably distended membranous intersegmental regions. are those suggested by female genitalic features (Sæther, 1977) Mensural features are tabulated to facilitate comparison. Unless to be close to Paralimnophyes, a genus to which Botryocladius indicated otherwise, measurements are in µm and rounded to shows some overall similarity, and the grouping to which some the nearest 5 µm except in cases where measurement at stages of Botryocladius will key. Other adult taxa with small maximum magnification provided accuracy to 1 µm. scalpellate acrostichals were included, as were two formally Many distribution data have been acquired from capture of undescribed taxa from Australia of putative generic rank drifting pupal exuviae. Geographical coordinates are cited to (Cranston, 1996) sharing some features with Botryocladius. Their nearest minute if map-derived, or to the second when taxon codes (“Son”) reflect only the discovery sequence (n) of GPS-derived. Locality data for Australia are cited in the “Sydney Orthoclads” (Cranston, 1996) and convey no following clockwise sequence: Northern Territory, Queensland, postulated phylogenetic relationship. All aforementioned taxa New South Wales, Victoria, Tasmania, South Australia, listed were scored for each life-history stage. Potentially-related north to south, followed by Western Australia, listed south to described taxa, e.g. Australian Kiefferophyes Freeman, are north. Unless specified otherwise, the collector is one or other excluded for lack of information concerning immature stages. or both of the authors, and repository is either Adult-only classification is rejected based upon empirical ANIC - Australian National Insect Collection, or evidence such as that of Sæther (1990a), who could not recover WAM (Western Australian Museum, under present care of a monophyletic Orthocladiinae, and Cranston & Edward (1998) junior author) for material from Western Australia. Other whose resolved Podonominae phylogeny collapsed for the repository abbreviations: BMNH - British Museum (Natural

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