Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70803 USA;
Am J Bot. 2004 Aug;91(8):1155-62. doi: 10.3732/ajb.91.8.1155.
Clidemia hirta is one of the most common woody invasive plants in mesic to wet forests in Hawaii, where it was introduced around 1940. The species is relatively uncommon by comparison in its native range of Central and South America and some Caribbean Islands. We examined genetic variation in allozymes of 20 C. hirta populations on four Hawaiian Islands to determine the introduction history. For comparison, we measured genetic variation in 20 native populations across Costa Rica. Mean levels of genetic variation in Hawaiian and Costa Rican populations were low compared to other woody or introduced plants (11.5-12.5% polymorphic loci, 2.05-2.50 alleles per polymorphic locus, and 0.045-0.063 expected heterozygosity). Most genetic diversity was held within rather than among populations in both areas (G(ST) = 0.120 and 0.271 in Hawaii and Costa Rica, respectively). Hawaiian populations had a high degree of genetic similarity, and no genetic differentiation was found among the four Hawaiian Islands sampled. These patterns of genetic variation in Hawaii suggest that no intraspecific hybridization of genotypes from different parts of the native range has occurred and that introductions to the different islands came from the same or similar source populations. The low levels of genetic diversity in parts of both the native and introduced ranges suggest that genetic variation is unrelated to invasiveness in C. hirta.
糙叶树是夏威夷中湿至湿润森林中最常见的木本入侵植物之一，于 1940 年左右引入。相比之下，在糙叶树的中美洲和南美洲以及一些加勒比岛屿的原生范围内，该物种相对较少。我们检查了四个夏威夷岛屿上 20 个糙叶树种群的等位基因同工酶的遗传变异，以确定引入历史。作为比较，我们测量了哥斯达黎加 20 个本地种群的遗传变异。与其他木本植物或引入植物相比，夏威夷和哥斯达黎加种群的遗传变异水平较低（11.5-12.5%多态性位点，2.05-2.50 个等位基因/多态性位点，0.045-0.063 个期望杂合度）。在这两个地区，大多数遗传多样性都存在于种群内部，而不是种群之间（夏威夷的 G(ST)为 0.120，哥斯达黎加的 G(ST)为 0.271）。夏威夷种群具有高度的遗传相似性，在所采样的四个夏威夷岛屿之间没有发现遗传分化。这些夏威夷遗传变异模式表明，不同原生范围内的基因型之间没有发生种内杂交，而且不同岛屿的引入来自相同或相似的源种群。在原生和引入范围的部分地区遗传多样性水平较低表明，遗传变异与糙叶树的入侵性无关。
