The taxonomy and distribution of Australian terrestrial tardigrades
thesisposted on 2022-03-28, 22:34 authored by Sandra Kaye Claxton
The terrestrial tardigrade fauna of Australia has been given scant attention in the past. This study was undertaken to collect and identify terrestrial tardigrade species from a wide a variety of habitats in Australia. This new taxonomic data set was then used to explore zoogeographic patterns and processes in eastern Australia. -- The first part of this study is concerned with the clarification of some taxonomic problems which arose during the course of the study, the solution of which was essential in order to delineate species boundaries. In the family Macrobiotidae, two genera, Minibiotus and Calcarobiotus, are remarkable for the high number of species recorded in Australia relative to other parts of the world. Within the genus Macrobiotus many new species within two groups, hufelandi and harmsworthi, are described and it is concluded that the nominal species in each case is not part of the Australian fauna. A new genus, Haptobiotus, is described in the family Macrobiotidae. -- In order to clarify species within the Diphascon (D.) pingue group, populations were subjected to multivariate analysis. The analysis resulted in the conclusion that only two species in that group, D. pingue and D. pinguiforme, have so far been found in Australia. The study also resulted in the synonymisation with D. pingue and D. pinguiforme of two previously described species from Australia. -- The discovery of a new genus, Milnesioides, provides an insight into the structure and function of the buccal apparatus of the rare monotypic genus Limmenius within the family Milnesiidae. A new genus. Lexia, is described in the subfamily Itaquasconinae along with other members of this group which has been under-recorded in Australia. The descriptions of three species in the genus Antechiniscus provides new morphological detail for this genus and provides additional evidence that the genus is found only in cool temperate regions in the southern hemisphere. -- The 161 species in 34 genera found in this study are described and line drawings provided. Of the 161 species, 59 are new to science and a further 16 have been published as new species during the course of the project. Also included are descriptions of an additional 21 species, recorded from Australia by other authors but not found in this study. Eleven of these species are probably misidentified. Keys to genera and species are supplied. -- A small but revealing study provides some preliminary data on tardigrade species associated with cryptogams or leaf litter on soil and sand. The detection of a rich fauna suggests that such habitats need to be examined if the full tardigrade fauna of Australia is to be documented. -- Data from 36 sites in eastern Australia containing 141 species were subjected to multivariate analysis in order to elucidate zoogeographic patterns of tardigrade communities. The study, although preliminary in many ways, showed a high correlation between tardigrade communities and core zoogeographic subregions in eastern Australia, e.g., a northern monsoonal, a nontropical south-eastern and a dry central-western subregion. Two distinct habitat types within the south-eastern subregion, cool temperate rainforest and limestone sites also support distinct species communities. Each tardigrade community consists of cosmopolitan, pantropical, oriental, southern hemisphere and Australian species. The degree to which each of these types contribute to each community is discussed in terms of the evolutionary history and the climatic regime (primarily temperature and length of dry periods) of each subregion and, to a limited extent by passive dispersal.