Cryptic diversity in vertebrates: molecular data double estimates of species diversity in a radiation of Australian lizards (Diplodactylus, Gekkota)

Abstract

A major problem for biodiversity conservation and management is that a significant portion of species diversity remains undocumented (the 'taxonomic impediment'). This problem is widely acknowledged to be dire among invertebrates and in developing countries; here, we demonstrate that it can be acute even in conspicuous animals (reptiles) and in developed nations (Australia). A survey of mtDNA, allozyme and chromosomal variation in the Australian gecko, genus Diplodactylus, increases overall species diversity estimates from 13 to 29. Four nominal species each actually represent multi-species complexes; three of these species complexes are not even monophyletic. The high proportion of cryptic species discovered emphasizes the importance of continuing detailed assessments of species diversity, even in apparently well-known taxa from industrialized countries.

Figure 1

(a) Map of Australia showing distribution of recognized species (grey squares) and new or candidate species (black triangles) in the genus Diplodactylus. Unrecognized taxa are found across the continent and show no clear patterns in environmental or geographical distribution. While Diplodactylus are absent from far southeastern and eastern Australia, the relative lack of samples from across the north reflects the remoteness and consequent lack of sampling effort in this region. (b) Maximum-likelihood tree from 797 bp of ND2 data calculated using the GTR+I+G model for the genus Diplodactylus showing recognized (italics), unrecognized (bold) and candidate species (bold with asterisk). Key nodes with high bootstrap support values (above 70) from 1000 repetitions using the -f a search function in RaxML are indicated by asterisks. GenBank numbers and locality details for individual specimens are given in appendix 1 of the electronic supplementary material.