Habitat differentiation between estuarine and inland Hibiscus tiliaceus L. (Malvaceae) as revealed by retrotransposon-based SSAP marker

摘要

Hibiscus tiliaceus L. (Malvaceae) is a pantropical coastal tree that extends to the tidal zone. In this study, the retrotransposon sequence-specific amplified polymorphism (SSAP) technique was used in order to understand the genetic variation between four population pairs of H. tiliaceus from repeated estuarine and inland habitat contrasts in China. The estuarine populations were consistently more genetic variable compared with the inland ones, which may be attributed to extensive gene flow via water-drifted seeds and/or retrotransposon activation in stressful estuarine environments. An AMOVA revealed that 8.9% of the genetic variance could be explained by the habitat divergence within site, as compared with only 4.9% to geographical isolation between sites, which indicates significant habitat differentiation between the estuarine and inland populations. The estuarine populations were less differentiated (Phi(ST) = 0.115) than the inland (Phi(ST) = 0.152) implying frequent gene interchange in the former. Accordingly, the principal coordinate analysis of genetic distance between individuals revealed that genetic relationships are not fully consistent with the geographic association. These results suggest that despite substantial gene flow via sea-drifted seeds, habitat-related divergent selection could be one of the primary mechanisms that drive habitat differentiation in H. tiliaceus at a local ecological scale.