Williams Dean A, Overholt William A, Cuda James P, Hughes Colin R
Department of Biology, University of Miami, Coral Gables, FL 33124, USA.
Mol Ecol. 2005 Oct;14(12):3643-56. doi: 10.1111/j.1365-294X.2005.02666.x.
Brazilian peppertree (Schinus terebinthifolius) is a woody perennial that has invaded much of Florida. This native of northeastern Argentina, Paraguay, and Brazil was brought as an ornamental to both the west and east coasts of Florida at the end of the 19th century. It was recorded as an invader of natural areas in the 1950s, and has since extended its range to cover over 280 000 ha. Our goals were to understand the history of this invasion, as one step toward understanding why this exotic was so successful, and ultimately to improve development of biological control agents. We sampled plants from the native and exotic ranges, particularly Florida, and genotyped these individuals at nuclear and chloroplast loci. Nuclear microsatellite and cpDNA loci reveal strong genetic population structure consistent with limited dispersal in the introduced and native ranges. Bayesian clustering of microsatellite data separates the east and west coast plants in Florida into distinct populations. The two chloroplast haplotypes found in Florida are also concordant with this separation: one predominates on the east coast, the other on the west coast. Analysis of samples collected in South America shows that haplotypes as distinct as the two in Florida are unlikely to have come from a single source population. We conclude that the genetic evidence supports two introductions of Brazilian peppertree into Florida and extensive hybridization between them. The west coast genotype likely came from coastal Brazil at about 27 degrees south, whereas the east coast genotype probably originated from another, as yet unidentified site. As a result of hybridization, the Florida population does not exhibit low genetic variation compared to populations in the native range, possibly increasing its ability to adapt to novel environments. Hybridization also has important consequences for the selection of biocontrol agents since it will not be possible to identify closely co-adapted natural enemies in the native range, necessitating more extensive host testing.
巴西胡椒树（Schinus terebinthifolius）是一种多年生木本植物，已入侵佛罗里达州的大部分地区。这种原产于阿根廷东北部、巴拉圭和巴西的植物在19世纪末作为观赏植物被引入佛罗里达州的东西两岸。20世纪50年代，它被记录为自然区域的入侵者，此后其分布范围扩大到超过28万公顷。我们的目标是了解这次入侵的历史，作为理解这种外来物种为何如此成功的第一步，并最终改善生物防治剂的开发。我们从本地和外来分布区，特别是佛罗里达州采集了植物样本，并对这些个体在核基因座和叶绿体基因座进行了基因分型。核微卫星和叶绿体DNA基因座揭示了强大的遗传种群结构，这与引入区和原生区有限的扩散一致。微卫星数据的贝叶斯聚类将佛罗里达州东西两岸的植物分为不同的种群。在佛罗里达州发现的两种叶绿体单倍型也与这种分离一致：一种在东海岸占主导，另一种在西海岸占主导。对在南美洲采集的样本分析表明，像佛罗里达州的这两种如此不同的单倍型不太可能来自单一的源种群。我们得出结论，遗传证据支持巴西胡椒树两次引入佛罗里达州并在它们之间广泛杂交。西海岸的基因型可能来自南纬约27度的巴西海岸，而东海岸的基因型可能起源于另一个尚未确定的地点。由于杂交，佛罗里达州的种群与原生范围内的种群相比并没有表现出低遗传变异，这可能增加了其适应新环境的能力。杂交对于生物防治剂的选择也有重要影响，因为不可能在原生范围内识别紧密共同适应的天敌，因此需要进行更广泛的寄主测试。
