Not being able to accurately identify species can have major implications for our understanding of biodiversity and for the setting of conservation priorities in particular. If all of the individuals in a region are thought to be one species, and 70 per cent of populations are lost due to disease or predation, it may not be catastrophic for this species’ overall survival. However, if these same individuals actually belong to a number of different species — each found only in different subregions but misidentified as the same species — then losing the majority of populations could mean the unacknowledged extinction of entire species.
Traditionally, morphological (physical) differences have been used as the basis for identifying different species. Increasingly scientists are recognising the limitations of morphology for discovering the existence of so-called ‘cryptic’ species — those that cannot be distinguished based on appearance alone.
Fortunately, a range of genetic technologies are now available to help researchers discover cryptic species. Mr Mark Adams from the Museum’s Evolutionary Biology Unit uses ‘allozyme electrophoresis’, one of the ‘oldest’ molecular genetic techniques, to test the validity of the existing taxonomy in a range of native species. While Mark has investigated species in groups as diverse as bats, butterflies and bacteria, his current focus/obsession involves Australia’s freshwater fishes.
One particular species, the mountain galaxias (Galaxias olidus) has been variously identified as between one and six species since it was first described in the 1800s. In the past, the traditional measurements and counts used to define fish species have been inconclusive for mountain galaxias. A review by the world taxonomic expert on this group of fishes determined they were all one species, albeit highly variable. Humans and dogs are both examples of highly morphologically variable species.
Allozyme electrophoresis conducted recently by Mark showed that there were in fact 15 species of mountain galaxias, some only found in the Murray-Darling basin, and others only in coastal rivers across eastern Victoria and southern New South Wales. Locally, two of these species co-occur on the Fleurieu Peninsula.
Mark’s collaborator Dr Tarmo Raadik (Arthur Rylah Institute for Environmental Research, Victoria) undertook traditional taxonomic work to look for morphological differences between the 15 candidate species (species that have not yet been named). Dr Raadik was able to use quantitative measurements of morphometrics — size and shape — to identify all 15 species.
Ecological differences between galaxias species were also identified. For example, Tarmo’s research has found that one species lives only in the ‘riffles’ of fast-flowing mountain streams in central Victoria. More importantly, several species survive only as remnant populations in single rivers; indeed one species is now restricted to several hundred metres of an isolated, narrow stream. Trout introduced for recreational fishing feed on the juveniles of these fishes, which could place this and other isolated species in grave danger of extinction.
Whether working on fish, frogs or fungi, a good proportion of Mark’s genetic analyses either validate the number of species identified by traditional approaches or discover new candidate species.
With candidate species, the Museum ‘voucher’ specimens that formed the basis of these genetic analyses can then be used to determine whether morphological differences can, with hindsight, be used to differentiate the species. The research has highlighted the value of genetic techniques for identifying cryptic species, but also emphasises how molecular studies complement, rather than replace, traditional taxonomic approaches.