The diversity and phylogenetic relationships of plants and animals inhabiting the
Australian Wet Tropics World Heritage Area have been studied recently to lay the groundwork for evolutionary and biogeographic analyses. Although insects represent a major component of Wet Tropics ecosystems, relatively little data are available on their current patterns of diversity and the processes that have led to these patterns. Before this project was initiated, intensive collecting of Wet Tropics rainforests revealed a high diversity of flightless beetles from the tenebrionid tribe Coelometopini (Insecta: Coleoptera). Because of the poor taxonomic knowledge on this tribe, it became clear that a major revision was needed before any significant evolutionary and biogeographic hypotheses could be derived. The main objectives of this thesis are to describe the diverse Coelometopini fauna from the Wet Tropics as well as provide a phylogenetic framework for the evolution of this group.
Firstly, I present a cladistic analysis of the Australasian Coelometopini (Coleoptera:
Tenebrionidae: Coelometopinae) in order to test how many lineages comprise the Wet Tropics fauna. A total of 101 morphological characters were coded for 50 species (which included members of most genera present in Australia, New Guinea, New Caledonia and the Pacific region). Results show that the Australasian Coelometopini comprises several well-supported clades and that the majority of flightless species from the Australian Wet Tropics form a single monophyletic lineage (genus Apterotheca Gebien).
The phylogenetic analysis of Australasian Coelometopini also indicates that the loss of flight has occurred independently in several clades. These results provided an excellent basis to study the evolution of the elytra-to-body binding mechanism in flightless taxa. Results of a comparative study of flightless Coelometopini from different clades indicate that overall, flightless Wet Tropics species have features that are more similar to macropterous tenebrionids than other flightless, rainforest tenebrionids studied previously. These investigations also provide data on the evolution and phylogenetic potential of the little studied elytra-to-body binding mechanism.
The taxonomic treatment of the Wet Tropics Coelometopini concentrated on two distinct clades. The new beetle genus Cuemus gen. nov. is described and illustrated. This genus, which contains two known species (C. monteithi sp. nov. and C. cooki, sp. nov.), is endemic to the high elevation rainforests of the Wet Tropics and belongs to a monophyletic group that includes Asopidiopsis Kaszab and Micromenandris Kaszab, both endemic to Fiji.
The genus Apterotheca Gebien, which is composed entirely of flightless species, is the most diverse low vagility insect genus known in the Wet Tropics region. Species of Apterotheca are mostly restricted to the high elevation rainforests. Forty-four species are included here in a revision of the genus. Three of these species were previously included in Apterotheca [A. amaroides (Pascoe), A. besti (Blackburn) and A. punctipennis Carter], four were previously included in other genera [A. australis (Kulzer) comb. nov. and A. punctifrons (Gebien) comb. nov. in Apterophenus Gebien; A. costata (Buck) comb. nov. in Caxtonana Buck and A. pustulosa (Carter) comb. nov. in Austropeus Carter] and 37 are new. The monotypic genera Austropeus Carter syn. nov. and Caxtonana Buck syn. nov. are proposed as new synonyms of Apterotheca. Lectotypes for A. punctipennis and A. besti are also designated. A key to the species of Apterotheca, a phylogenetic analysis based on the morphological features of adults as well as a discussion of character evolution are also included.
The last research chapter represents the first attempt to elucidate the patterns of speciation and community assemblage in arthropods of the Australian Wet Tropics. For this purpose, I use phylogenetic and distributional data from the genus Apterotheca as well as from other published revisions on Wet Tropics arthropods. The region is divided into 17 areas of endemism (isolated patches of high elevation rainforests) for the biogeographic analysis. These areas of endemism were based on data from palaeoclimatic reconstructions (Nix and Switzer 1991) as well as from the distribution of more than 300 species of arthropods (Monteith 1995; Yeates et al. in press). A combination of primary and secondary BPA (Brooks Parsimony Analysis) is used. The results obtained from the historical biogeography analysis indicate the following patterns of evolution: 1) there is no support for a single pattern of area relationships for the 87 species included in the analysis; 2) three independent area relationships are needed to explain the data; 3) vicariance is not the principal mode of speciation; 4) within-area speciation is common; 5) across-area peripheral isolate speciation accounts for a significant number of events; 6) all 17 areas of endemism have reticulate histories; 7) widespread species occupy between two and ten areas of endemism and 8) in each of the three secondary BPA area cladograms, there is a single clade which becomes associated with other clades through colonisation. These patterns of evolution support the "taxon pulse" model previously proposed by Erwin (1979, 1981, 1985; Erwin and Adis 1982).