GENETIC-VARIATION, ITS ASSESSMENT AND IMPLICATIONS TO THE CONSERVATION OF SEAGRASSES

In a study of the widespread Australian endemic seagrass Posidonia aus tralis, allozyme analysis identified a wide range in population geneti c structure assessed using the multilocus genotype diversity statistic (DG). Values of DG between zero and one were obtained; however, RAPD analysis generally detected higher levels of diversity, where DG value s were all greater than 0.5 (D-G = 0.67 - 1). Some populations were al lozymically monomorphic using allozyme analysis yet were highly polymo rphic using RAPD analysis. The differences observed between methods, p articularly among allozymically uniform populations, demonstrate the i mportance of choosing an appropriate method when assessing genotypic d iversity. Different methods may reflect different historical aspects o f population processes where allozymes reflect broader-scale gene flow and population establishment and DNA fingerprinting methods such as R APDs may reflect fine-scale local recruitment events and shorter-term population processes. Using either method alone, particularly in genot ypically depauperate organisms such as seagrasses and other clonal org anisms, will be problematic in assessing their population genetic pote ntial, a parameter being used by conservation managers to decide upon management strategies in rare and endangered organisms. It is recommen ded that the impact of disturbance assessed using genotypic diversity measures requires more than one technique to provide the most appropri ate information for designing subsequent conservation strategies.