Land reptiles are known from at least 53 islands and cays of the GBR and include at least 31 species of lizards and nine species of terrestrial snakes. Detailed treatment of this fauna is beyond the scope of this chapter and only a summary is presented here.
The fauna of the continental islands is a subset of that of the Queensland coast. The geology, soils and vegetation of continental islands resemble conditions on the adjacent mainland and in many cases the islands and mainland were connected as recently as 10 000 years ago during the most recent Pleistocene glacial maximum, when sea levels were over 100 metres lower than present levels. Some reptiles are moderately adept at over-water dispersal and, although populations may have been separated since rising sea levels isolated continental islands, it is likely that at least some gene flow has persisted since then. Consequently, most of the populations of lizards and snakes on continental islands of the GBR region are not insular endemics, but are conspecific with mainland populations. The herpetofauna of continental islands encompasses a variety of lizards including mainly skinks (Scincidae) and geckos (Gekkonidae) as well as some flap-footed lizards (Pygopodidae) and goannas (Varanidae). Indeed, Lizard Island was named after its population of goannas. Dragons (Agamidae) are notably lacking. Small numbers of species of all the terrestrial families of Australian snakes are represented on continental islands in the GBR region.
The coral cays have a lower species richness of terrestrial reptiles than do the continental islands. Their fauna is composed of two elements, skinks and geckos that are readily dispersed over water naturally as waifs and which also are widely dispersed on islands well beyond the GBR region, and skinks and geckos that have been transported to the cays by human agency. In addition, there have been a few species of dragons inadvertently introduced by humans; these were ephemeral and did not establish permanent populations.
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