Diversity in parasitic helminths of Australasian marsupials and monotremes: a molecular perspective

Marsupials and monotremes are a prominent part of the mammalian fauna in Australia, and harbour an extremely diverse and highly distinctive array of helminth parasites. Their study has been relatively neglected, likely because they have no direct, adverse socioeconomic impact. As the body plans of helminths generally are very simple and morphological characterisation likely underestimates true diversity, molecular tools have been employed to assess genetic diversity. Using biochemical and/or molecular methods, recent studies show extensive diversity in helminths of marsupials, with cryptic species being commonly encountered. The purpose of this article is to review current knowledge about the diversity of parasitic helminths of marsupials and monotremes, to raise questions as to whether current molecular data can be used to estimate diversity, what mechanisms lead to such diversity, to critically appraise the molecular tools that have been employed thus far to explore diversity and to discuss the directions which might be taken in the future employing improved techniques.