Abstract：
OBJECTIVE: The sessile-flowered Trillium species from western North America have been challenging to distinguish morphologically due to overlapping characters and intraspecific variation. Molecular phylogenetic analyses, currently inconclusive for this group, have not sampled multiple populations of the different species to account for this. Here, we query the diversity of floral volatile composition to understand its bearings on the taxonomy, distribution and evolution of this group.
METHODS: We explored taxonomic and geographic patterns in average floral volatile composition (105 different compounds) among 42 wild populations of four sessile-flowered Trillium species and the outgroup, Pseudotrillium, in California, Oregon and Washington by means of parsimony-constrained phylogenetic analyses. To assess the influence of character construction, we coded compound abundance in three different ways for the phylogenetic analyses and compared the results with those of statistical analyses using the same dataset and previously published statistical analyses.
RESULTS: Different codings of floral volatile composition generated different phylogenetic topologies with different levels of resolution. The different phylogenies provide similar answers to taxonomic questions but support different evolutionary histories. Monophyly of most populations of each taxon suggests that floral scent composition bears phylogenetic signal in the western sessile-flowered Trillium. Lack of correlation between the distribution of populations and their position in scent-based phylogenies does not support a geographic signal in floral scent composition.
CONCLUSIONS: Floral scent composition is a valuable data source for generating phylogenetic hypotheses. The way scent composition is coded into characters is important. The phylogenetic patterns supported by floral volatile compounds are incongruent with previously reported phylogenies of the western sessile-flowered Trillium obtained using molecular or morphological data. Combining floral scent data with gene sequence data and detailed morphological data from multiple populations of each species in future studies is needed for understanding the evolutionary history of western sessile-flowered Trillium.
METHODS: We explored taxonomic and geographic patterns in average floral volatile composition (105 different compounds) among 42 wild populations of four sessile-flowered Trillium species and the outgroup, Pseudotrillium, in California, Oregon and Washington by means of parsimony-constrained phylogenetic analyses. To assess the influence of character construction, we coded compound abundance in three different ways for the phylogenetic analyses and compared the results with those of statistical analyses using the same dataset and previously published statistical analyses.
RESULTS: Different codings of floral volatile composition generated different phylogenetic topologies with different levels of resolution. The different phylogenies provide similar answers to taxonomic questions but support different evolutionary histories. Monophyly of most populations of each taxon suggests that floral scent composition bears phylogenetic signal in the western sessile-flowered Trillium. Lack of correlation between the distribution of populations and their position in scent-based phylogenies does not support a geographic signal in floral scent composition.
CONCLUSIONS: Floral scent composition is a valuable data source for generating phylogenetic hypotheses. The way scent composition is coded into characters is important. The phylogenetic patterns supported by floral volatile compounds are incongruent with previously reported phylogenies of the western sessile-flowered Trillium obtained using molecular or morphological data. Combining floral scent data with gene sequence data and detailed morphological data from multiple populations of each species in future studies is needed for understanding the evolutionary history of western sessile-flowered Trillium.
摘要：
目的：由于重叠的特征和种内变异，来自北美西部的固着花延龄草物种在形态上难以区分。分子系统发育分析,目前这个群体没有定论，没有采样不同物种的多个种群来解释这一点。这里,我们询问花卉挥发性成分的多样性，以了解其对分类学的影响，这个群体的分布和演变。
方法：我们探索了四种固着花延龄草和外群的42个野生种群的平均花卉挥发性成分（105种不同化合物）的分类学和地理模式，假延菌,在加州,俄勒冈州和华盛顿州通过简约约束的系统发育分析。为了评估角色建构的影响，我们以三种不同的方式编码了化合物丰度,用于系统发育分析,并将结果与使用相同数据集和以前发表的统计分析的统计分析结果进行了比较.
结果：花挥发性成分的不同编码产生了具有不同分辨率水平的不同系统发育拓扑。不同的系统发育为分类学问题提供了相似的答案，但支持不同的进化史。每个分类单元的大多数种群的单一性表明，花香成分在西方固着花的延龄草中具有系统发育信号。种群分布与其在基于气味的系统发育中的位置之间缺乏相关性，不支持花香成分中的地理信号。
结论：花香成分是产生系统发育假设的有价值的数据来源。将气味成分编码为字符的方式很重要。花卉挥发性化合物支持的系统发育模式与先前报道的使用分子或形态数据获得的西方固着花延龄草的系统发育不一致。在未来的研究中，需要将花香数据与基因序列数据以及来自每个物种多个种群的详细形态数据相结合，以了解西方固着花延龄草的进化史。
方法：我们探索了四种固着花延龄草和外群的42个野生种群的平均花卉挥发性成分（105种不同化合物）的分类学和地理模式，假延菌,在加州,俄勒冈州和华盛顿州通过简约约束的系统发育分析。为了评估角色建构的影响，我们以三种不同的方式编码了化合物丰度,用于系统发育分析,并将结果与使用相同数据集和以前发表的统计分析的统计分析结果进行了比较.
结果：花挥发性成分的不同编码产生了具有不同分辨率水平的不同系统发育拓扑。不同的系统发育为分类学问题提供了相似的答案，但支持不同的进化史。每个分类单元的大多数种群的单一性表明，花香成分在西方固着花的延龄草中具有系统发育信号。种群分布与其在基于气味的系统发育中的位置之间缺乏相关性，不支持花香成分中的地理信号。
结论：花香成分是产生系统发育假设的有价值的数据来源。将气味成分编码为字符的方式很重要。花卉挥发性化合物支持的系统发育模式与先前报道的使用分子或形态数据获得的西方固着花延龄草的系统发育不一致。在未来的研究中，需要将花香数据与基因序列数据以及来自每个物种多个种群的详细形态数据相结合，以了解西方固着花延龄草的进化史。
