ISSR-based genetic diversity of Casuarina spp. in coastal windbreaks of Taiwan

摘要

The Genus?Casuarina?is a coastal plant distributed throughout South East Asia, Australia, and the Pacific islands. In Taiwan, more than 10 species of?Casuarina?have been introduced based on the proposition that these drought tolerant, fast growing trees would be suitable for windbreaks and would help stabilize coastal sand. The genetic diversity of three?Casuarina?species grown in Taiwan,?Casuarina equisetifolia,?C.glauca,?and?C.?cunninghamiana?was determined and compared to those of native populations grown in Australasia as part of an international provenance test using the Inter-Simple Sequence Repeat (ISSR) marker system. Based on our results, the average Nei gene diversity of?Casuarina?grown in Taiwan (0.1940) is considerably higher (p < 0.001) than that of native populations of?C. equisetifolia?(0.1288),?C. cunninghamiana?(0.0922), and?C. glauca?(0.0577). Cluster and principal component analyses indicated that the Taiwan-grown trees are more closely related to?C. equisetifolia?than either?C. cunninghamiana?or?C. glauca. By integrated reasoning of? genetic variation and branchlet morphology, we may conclude that coastal?Casuarina?plants currently survived and grown in Taiwan are the products of introgressive hybridization involving?C. equisetifolia,?C. glauca, and possibly?C. cunninghamiana.