A note on life-history traits and conservation concerns for viviparous Australian seastars (Parvulastra parvivipara and P. vivipara)

The asterinid seastars Parvulastra parvivipara and P. vivipara share atypical viviparous reproductive modes that have made them of interest for research on life-history evolution and population genetics. This article briefly reviews life-history traits of these endemic Australian species and information on distribution and rarity, as well as providing some additional new analysis. Almost exclusive self-fertilisation has led to extreme genetic poverty in both species and viviparity limits dispersal potential causing relatively small geographical ranges. There is some evidence that the number of intertidal boulder-fields harbouring P. parvivipara, and the overall geographical range, may have become reduced in recent years. In addition, approximately 25 % of boulder-fields with P. parvivipara have been colonised by invasive oysters (Magallana gigas). To understand potential effects of oysters on P. parvivipara, we tested for correlations between P. parvivipara abundances and cover of oyster encrustations that included this invader (native + non-native oyster shells were assessed together because they produced similar encrustations and largely could not be differentiated). Linear regression showed no evidence, however, for any correlation. For P. vivipara, population survey data from the mid 1970's to present shows marked decline in areas of previous abundance. Parallel with this decline, the boulder habitat has experienced infill and siltation and cementing of the substratum by M. gigas, sponges and other encrusters as well as anoxia. Important future research outcomes on consequences of atypical life-history traits may be allowed by continued research on these seastars but only if their populations are able to persist within the small number of boulder-fields where they occur. Current trends may indicate a need for conservation intervention.