Molecular survey of the red algal family Rhodomelaceae (Ceramiales, Rhodophyta) in Australia reveals new introduced species

Red algae are frequently dominant components of the non-native biotas in coastal areas. They often remain undetected because of morphological similarity between native and introduced species and cryptic diversity. Routine use of DNA barcodes can aid in setting baseline tabulations of native species and for detecting introduced species. We performed an extensive survey of the red algal family Rhodomelaceae in southern Australia, producing a dataset containing more than 1100 rbcL sequences. The objective of this study was to screen that dataset for introduced species of the tribes Polysiphoniaeae and Streblocladieae, and to provide morphological information of presumably introduced species that were not previously recorded in Australia. Molecular data and morphological observations confirmed the presence of five presumably introduced species: Leptosiphonia brodiei, Melanothamnus japonicus, M. strictissimus, Polysiphonia morrowii and P. delicata. Polysiphonia morrowii and M. strictissimus were detected for the first time in Australia, and M. japonicus and P. delicata were found to be more widely distributed than previously known. Somewhat unexpectedly, the distribution range of L. brodiei has apparently shrunk, with our survey suggesting it remains only in Tasmania. Four of these species have been reported as introduced species in other countries, but M. strictissimus is here recorded for the first time outside its native New Zealand. Although all five species can be considered introduced or cryptogenic, only P. morrowii, M. japonicus and M. strictissimus were locally abundant, and further work will be needed to assess their ability to spread and effect negative impacts on native biotas.