Studies on the taxonomy of Australasian species of Culicoides Latreille (Diptera:Ceratopogonidae)

Abstract

The biting midge genus Culicoides contains approximately 1300 species worldwide. Many species are of economic importance either as biting pests of humans or domesticated animals or as vectors of pathogens for these hosts. The Australasian fauna contains a high proportion of undescribed species, most of which have not been formally placed into subgenera. Furthermore, many of the described species have not been revised since their original description and for these species data is lacking for several characters routinely used in modern descriptions, particularly the details of antennal sensilla. Additionally, several species are known only from a single sex. No tools are available to assist workers in recognising species of Australasian Culicoides. No Australasian specimens have undergone genetic analyses either to support specific status, monophyly of groupings or investigations into phylogeography. Using a modern suite of characters, morphological analyses of the known fauna of Australasia, including undescribed species, was used to complete a preliminary subgeneric classification of the Australasian Culicoides fauna. Wing photographs of all recognised species were compiled into a wing picture atlas which also provides a checklist of species and their subgeneric placement accompanied by a table of numerical values of described species. From the subgeneric classification proposed in the wing picture atlas, seven subgeneric groupings viz the Marksi, Bancrofti, Immaculatus, Molestus, Coronalis, Kusaiensis and Imicola groups, were fully revised including a group diagnosis, descriptions of new species, redescriptions of adult males and females and, where necessary, pupae. Species descriptions and group monophyly were supported where possible by COI and CAD molecular data. Included in these revisions are redescriptions of 17 existing species namely Culicoides marksi, C. dycei, C. parvimaculatus, C. pseudostigmaticus, C. immaculatus, C. agas, C. kusaiensis, C. paragarciai, C. leei, C. bancrofti, C. hornsbyensis, C. coronalis, C. molestus, C. subimmaculatus, C. submagnesianus, C. brevitarsis and C. nudipalpis, including a first description of the male of five species, C. bancrofti, C. immaculatus, C. molestus, C. submagnesianus and C. coronalis. Additionally, 12 new species are described being C. zentae, C. kayi, C. shivasi, C. collesi, C. nigritrans, C. balhorni, C. mabelae, C. mindjirri, C. roperi, C. septimus, C. reyei and C. asiatica. COI and/or CAD data are provided to support the specific status of the following 15 species C. immaculatus, C. shivasi, C. coronalis, C. nigritrans, C.molestus, C. reyei, C. balhorni, C. mindjirri, C. mabelae, C. brevitarsis, C. asiaticus, C. nudipalpis, C. kusaiensis, C. leei and C. paragarciai. Morphological analysis of the Marksi group found it to be sufficiently different from existing subgenera to warrant erection as a formal subgenus, C. subg. Marksomyia. Analysis of the remaining groupings found that although they appear to be unique, there is insufficient clarity around the limits of existing subgenera to justify the erection of these groupings as new subgenera. This problem is confounded by the lack of any formal phylogenetic study of the genus to test the monophyly of existing subgenera or the phylogenetic significance of many of the characters used to define subgenera. A combination of COI, CAD and morphological data was, however, useful in supporting the monophyly of the Imicola complex of C. subg. Avaritia and this model could also be useful in testing the monophyly of other groupings. Confirmation of the monophyly of the Imicola complex allowed interpretation of two synapomorphies for this complex, one in the male genitalia and one in the distribution of antennal sensilla of the male. Molecular data was used to associate adult male and female specimens of several species and revealed that specimens morphologically consistent with the male of C. ardentissimus were conspecific with females referable to C. paragarciai. This association required the movement of C. paragarciai from the Ornatus group to the Kusaiensis group and the removal of C.ardentissimus from the Kusaiensis group. Varying degrees of feminisation of the male antenna were observed across species which may be related to mating and swarming behaviour. A correlation was observed between feminisation of the male antenna and the shape of the male wing although the significance of this association is unclear. The structure of the spermathecal ducts was investigated and thedifferences observed may prove useful in future phylogenetic analyses.