Gnammas in central Victoria occur in scattered groups hidden away at Kooyoora, Terrick Terrick, Mt Pilot and Bald Rock. Compared to those in WA and SA, most pan and pit gnammas are small and shallow and occur in relatively young granites (450 MYBP), but some pits at Terrick Terrick are large. Waters are fresher than in those elsewhere and fill just as reliably, but hydroperiods are shorter. The study involved 50 sites visited 5-8 times over 3 years.
Momentary species richness varies from 2.7 species in the very shallow, windswept pans of Bald Rock, to 6.5 in the more benign Kooyoora pans, to 9.3 in the larger pans of Terrick Terrick which has a further advantage of being in a field of artificial pools which readily provide dispersants. Kooyoora pits average 7.6 MSR but the unusually large Terrick Terrick pits average 15.3 MSR. These figures are mostly significantly fewer than the figures of ca. 30 for pans and 12 for pits in the WA Wheatbelt and ca.10 and 9 respectively for pans and pits of Eyre Peninsula, SA. Furthermore, central Victorian gnammas have no endemics compared to many in WA and a few in EP. In addition, only a few species appear to have special adaptations for life in the Victorian gnammas, compared to many in WA.
Factors thought to be influencing these differences include habitat size (a function of site age), number of gnammas per rock exposure (provides habitat variability and availability), and past climatic fluctuations (promotes speciation). All these factors enhance diversity in WA, but mostly inhibit it in central Victoria, with EP in between and closer to central Victoria geographially and biologically.