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The smaller of the two gasteruptiid subfamilies, Hyptiogastrinae has a restricted Gondwanan distribution, being found on the Australian mainland, Tasmania, New Zealand and South America, as well as New Caledonia, New Guinea, Fiji and Vanuatu (Jennings and Austin 1994a,b, 1997a, 2002). Jennings and Austin (2002) recently reduced the number of genera from five to two on phylogenetic grounds (Hyptiogaster and Pseudofoenus s.l.), and more than doubled the number of described species to 88; most of these species are found in Australia.
Hyptiogaster is endemic to mainland Australia and does not occur in Tasmania. The genus appears to be restricted to eastern and western subtropical, temperate, Mediterranean and semi-arid areas, and is absent from the tropical north and arid interior parts of the continent. The other genus in this subfamily, Pseudofoenus, is most diverse in south-western Western Australia (Jennings and Austin 1997a).
The distribution of hyptiogastrines is indicative of one that has largely been determined by vicariance events associated with the breakup of the Gondwanan supercontinent, and hence would provide a date for the early radiation of the group of about 65 mya. Preliminary phylogenetic analysis of the subfamily by Jennings and Austin (2002), however, suggest that their current continental distribution may have been determined by dispersal events.
When the Australian hyptiogastrine fauna is examined in more detail (Fig. 1), most species are seen to be restricted to a single region, with only 15 species (19%) being found in more than two regions. The highest species richness occurs in the Western Bassian Region (24 endemic spp.), followed by the Eastern Bassian (16 spp., including Tasmania) and the Eyrean (6 spp.). When undescribed species are taken into account (of which there are about 30 species) the proportion of endemic taxa for the Western Bassian increases even further, as approximately half these undescribed species are known only from this area. Interestingly, very few species are restricted to the Torresian Region and none of these are shared with New Guinea.
Fig.1 Number of hyptiogastrine species endemic (in circles) to particular biogeographic regions of Australia, and numbers of species shared between them (in boxes). Species that occur in more than two regions or those shared between disjunct regions not indicated. (Adapted from Jennings & Austin 2002)