FNZ 68 - Simuliidae (Insecta: Diptera) - Future studies on Austrosimulium
Craig DA, Craig REG, Crosby TK 2012. Simuliidae (Insecta: Diptera). Fauna of New Zealand 68, 336 pages.
(
ISSN 0111-5383 (print),
ISSN 1179-7193 (online)
;
no.
68.
ISBN 978-0-478-34734-0 (print),
ISBN 978-0-478-34735-7 (online)
).
Published 29 June 2012
ZooBank: http://zoobank.org/References/9C478D54-FEB2-45E8-B61C-A3A06D4EB45D
There are still many opportunities for research on Austrosimulium. At a higher level, the Australian segregate needs to be fully revised to the same level as done here for New Zealand, together with molecular analyses. Part of that revision might well include the so-called Paracnephia Rubtsov of Australia. There are also indications that the New Zealand Austrosimulium might be paraphyletic, with a separate origin for the ungulatum-subgroup given its unusual pupal gill structure.
Within New Zealand a more detailed examination of the human-biting species A. australense is in order, to see if morphological evidence can be found to assign the South Island population to a separate morphospecies from that of the North Island. This would resolve the current taxonomic conundrum from molecular analysis of the australense species-group (Fig. 509a, 509b, 510) with A. longicorne, a markedly distinct morphospecies, sister to the South Island clade of A. australense, but not to the whole of A. australense. Part of this examination should involve further collections of A. australense from around the north of the South Island, to clarify the occurrence of North Island haplotypes there (Fig. 511), and also collections in the south of the South Island and on Stewart Island (Fig. 511, 512). Such study should help to clarify aspects of historical biogeography.
Similarly, the important human-biting species A. ungulatum needs further examination, particularly the variation in its pupal gill structure. Molecular evidence indicates that A. ungulatum is a species complex and the gills might provide sufficient morphological evidence to assign some haplotypes to separate species. Such an examination should also include a re-examination of the relationship of A. vexans to its sister segregate of A. ungulatum. More material of A. campbellense is needed to answer the following question; is it directly sister to A. vexans, or is it related to a segregate of A. ungulatum haplotypes, as is A. vexans?
It is of phylogenetic significance to find the immature stages of A. dumbletoni and A. vailavoense, currently assigned to the ungulatum species-group on the basis of their morphology. In contrast, molecular evidence indicates both belong to the unicorne-subgroup. Early stages, in particular the pupae, could resolve to which subgroup they should really be assigned. Searches for A. dumbletoni immatures might well be concentrated in high-altitude localities, in keeping with known habitats of the unicorne-subgroup species; none have thus far been found at low altitude where adults have been collected.
High-altitude localities need to be further searched. They have been relatively poorly collected to date because of access difficulties. Such collections would no doubt reveal that some of the current disparate distributions, such as those for A. albovelatum and A. fiordense, are probably the result of lack of collecting. Areas that need much more collecting are southern Southland and Stewart Island, as simuliids from both regions indicate that these regions were refugia during glaciations. The central Marlborough region, with poor access, is also an area of concern — virtually no collections are known from there.
Ecologically, almost all species, with the exception of A. tillyardianum and perhaps A. australense, need detailed study; even the most basic investigation would add to current knowledge. One species, A. longicorne, would be most intriguing to investigate further. Originally thought to be widespread and disparate in distribution, it is now known to be widespread and common on the central volcanoes of the North Island. Of particular interest is the extreme habitat of the larvae: thin-film, slow-velocity flows in seepages dominated by iron bacteria. The larvae are the dominant aquatic macroinvertebrate in these habitats. One aspect of biology that is startlingly undocumented for all species is mating behaviour; what do the males do and where does copulation take place?
Ilmonen et al. (2009) successfully used multiple characters from cytology, CO1 gene sequences, ecology, and morphology to clarify species status within the European Simulium vernum group. A similar approach could perhaps be used to better elucidate species limits within the tillyardianum species-group of Austrosimulium, in particular those of the ‘multicorne assemblage’, which appears to be undergoing an evolutionary radiation. Rubinoff et al. (2006) pointed out that nuclear genes might provide insights into relationships when mtDNA does not.
Molecular evidence showed that a haplotype from the top of the Takaka Hill, was sister to the australense-subgroup, but morphologically it appeared to be A. longicorne. Further collecting from that locality might throw some light on this conundrum.
In the central North Island, further investigations are needed on A. australense to explain the abrupt change in heterozygote inversion pairs between Zones 1 and 2 reported by McLea & Lambert (1983, 1985); they suggested this might represent 2 cryptic species with support provided by differing water flow conditions in the habitats the larvae occupied. However, we found no morphological evidence to substantiate the presence of 2 cryptic species, and molecular analysis of the CO1 gene also did not support it. In South Westland it would be worth investigating why this species showed a high ratio (about 1 in 170) of gynandromorphic individuals attracted to moulting Fiordland crested penguins in one study (Craig & Crosby 2008); this incidence of gynandromorphic individuals is far higher than reported for any other simuliid species (Crosskey 1990).