Molecular identification of natural hybridization between and in Sarawak, Malaysia.

Hybridization is very common in flowering plants and it plays a significant role in plant evolution and adaptation. L. (Melastomataceae) comprises about 80-90 species in tropical Asia and Oceania, among which 41 species occur in Borneo. Natural hybridization is frequently reported in in China, but so far there have been no confirmed cases of hybridization in Southeast Asia (including Borneo), where most species occur. Here, we identified a case of natural hybridization between L. and Cogn. in Sarawak, Malaysia, by using sequence data of three nuclear genes and one chloroplast intergenic spacer. is the most widespread species of this genus, occurring in almost the whole range of this genus, while is a local species endemic to northern Borneo. Our results showed that natural hybridization and introgression occur between and , and the introgression was asymmetrical, mainly from to . As adaptive traits can be transferred by introgression, our study suggests that natural hybridization should be a significant mechanism for the evolution and adaptation of in Southeast Asia. However, introgression from the common species to the relatively rare species may cause the decline of , incurring conservation concern. With a large number of species of and almost year-around flowering in Southeast Asia, more cases of natural hybridization are expected to be found and identified in near future.