Craig D. James

Why are there so many coexisting species of lizards in Australian deserts

Abstract Because Australian skinks of the genus Ctenotus display very high local species richness in arid-zone spinifex grasslands but not in mesic habitats, these lizards have been used as ”model organisms” to ask why ecologically similar taxa coexist under some circumstances but not others. Previous work has involved detailed studies within small areas, and has looked for differences in ecological processes between arid versus mesic habitats. We suggest a radically different explanation for the high species-richness of arid-zone Ctenotus, by shifting attention to a larger spatial scale: the regional species pool. Analyses of the geographic distributions of Ctenotus species confirm that more species coexist at sites in the arid-zone (mean =9.3 species per site) than in other climatic zones (means 2.4–7.6). However, the total number of species occurring within the arid-zone is actually lower, per km2 of habitat, than is the case in some other climatic zones. That is, arid-zone Ctenotus show a higher local (alpha) species diversity, but a lower regional (gamma) diversity, than their mesic-habitat congeners. This apparent paradox occurs because most arid-zone species occur over vast areas (mean =1,035,000 km2), whereas congeners from other climatic zones have smaller geographic ranges (200–373,000 km2). The broad distributions of arid-zone taxa reflect the great spatial homogeneity in climatic conditions in this zone. That is, the ”climate spaces” occupied are similar for Ctenotus species from all bioclimatic regions. Thus, a given amount of climatic space translates into a larger geographic distribution (and hence, more sympatry) in the arid-zone than in other areas. In summary, the high number of coexisting Ctenotus species in arid-zone habitats may simply reflect the facts that the arid zone is large (so that many species have evolved therein) and climatically homogeneous (so that any species evolving in that habitat type can disperse very widely, and thus overlap with many other species). Our approach explains much of the variance in local-assemblage species richness from regional to site scales; but explanations invoking biological attributes of the species concerned, the nature of their interactions with other species or with particular resources (such as prey or shelter) may still be significant at microhabitat scales. For lizard communities in Australia, species richness at a site may be determined more by continental biogeography rather than by ecological interactions.

Distributed Collaborative Immersive Virtual Reality Framework for the Mining Industry

This paper describes a framework for experiments in Human-Computer Interaction, using immersive virtual reality, computer vision and other sensors, and remote collaboration. The proposed framework is demonstrated in a number of applications.

Seven lizard species and a blind snake: activity, body condition and growth of desert herpetofauna in relation to rainfall

In the Australian arid zone, primary productivity is highly variable in response to irregular and unpredictable rainfall and this has major flow-on effects for desert fauna. We measured temporal patterns of activity and body condition of eight reptile species, and growth for the three most abundant species, in a dry and a wet year. Activity and body condition of the diurnal lizards Ctenophorus nuchalis and Amphibolurus gilberti (Agamidae) and Ctenotus leonhardii and Ctenotus schomburgkii (Scincidae) varied predictably. In the dry year the onset of warm-season activity was delayed and body condition was low, whereas high levels of activity and body condition were observed in the wet year. Growth rates of C. schomburgkii, C. leonhardii, and C. nuchalis did not differ between the two years. Body condition of the nocturnal lizards Diplodactylus conspicillatus and Rhynchoedura ornata (Gekkonidae) and Lerista labialis (Scincidae) did not differ between years but the nocturnal blind snake Ramphotyphlops centralis (Typhlopidae) had higher condition in the wet year. Nocturnal species were active only in warmer months and this apparently limited their ability to respond to favourable conditions in the wet year. Temporal patterns of activity may be important determinants of how effectively lizards can make use of available resources after rain.

The science of desert living: building livelihoods and protecting landscapes

Credit: Ninti One Deserts are special: not only for the rich life they contain and the intricacy of their functioning, but also for the unique ways in which humans adapt to desert living. Living in deserts is challenging enough in itself, but is made harder still by: marked cultural differences 1. distinctive local knowledge 2. social uncertainty 3. isolation from centres of political and economic decision. 4.