Molecular genetic variation and structure of Southeast Asian crocodile (Tomistoma schlegelii): Comparative potentials of SSRs versus ISSRs

Tomistoma schlegelii, also referred to as the "false gharial", is one of the most exclusive and least known of the world's fresh water crocodilians, limited to Southeast Asia. Indeed, lack of economic value for its skin has led to neglect the biodiversity of the species. The current study aimed to investigate the mentioned case using 40 simple sequence repeat (SSR) primer pairs and 45 inter-simple sequence repeat (ISSR) primers. DNA analysis of 17 T. schlegelii samples using the SSR and ISSR markers resulted in producing a total of 49 and 108 polymorphic bands, respectively. Furthermore, the SSR- and ISSR-based cluster analyses both generated two main clusters. However, the SSR based results were found to be more in line with the geographical distributions of the crocodile samples collected across the country as compared with the ISSR-based results. The observed heterozygosity (HO) and expected heterozygosity (HE) of the polymorphic SSRs ranged between 0.588-1 and 0.470-0.891, respectively. The present results suggest that the Malaysian T. schlegelii populations had originated from a core population of crocodiles. In cooperation with the SSR markers, the ISSRs showed high potential for studying the genetic variation of T. schlegelii, and these markers are suitable to be employed in conservation genetic programs of this endangered species. Both SSR- and ISSR-based STRUCTURE analyses suggested that all the individuals of T. schlegelii are genetically similar with each other.