Floral scent of Joshua trees (Yucca brevifolia sensu lato): Divergence in scent profiles between species but breakdown of signal integrity in a narrow hybrid zone.
Floral scent of Joshua trees (Yucca brevifolia sensu lato): Divergence in scent profiles between species but breakdown of signal integrity in a narrow hybrid zone.
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DOI：
10.3732/ajb.1600033
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发表时间：
2016-10
影响因子：
3
通讯作者：
G. Svensson;R. Raguso;R. Flatz;Christopher I. Smith
中科院分区：
文献类型：
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作者：
G. Svensson;R. Raguso;R. Flatz;Christopher I. Smith
研究的前提花香在促进密切相关的植物之间的生殖隔离的作用仍然知之甚少。短叶丝兰和丝兰在异域中由不同的蛾类授粉，但在狭窄的接触区，传粉者-宿主特异性被打破，导致物种间的杂交。我们探讨了生殖隔离和杂交在这些约书亚树的化学基础，通过表征花的气味，每个物种在异地，分析气味配置文件中的接触区的树木，并匹配这些数据与基因型和表型数据。方法：我们分析了花挥发性物质，使用气相色谱-质谱法，测试的气味配置文件的物种分歧和分类的树木在接触区的杂交或亲本物种。我们使用花和营养形态数据和基因型数据进行树木分类，并分析某些性状组合是否比其他人更相关的树木分配和分类树类型的频率是否不同，这取决于使用的数据集。关键结果约书亚树的花香包括其他丝兰中没有报道的含氧8碳化合物。两种鸟类在气味特征上存在显著差异（P < 0.001）。在接触区，发现了许多杂交种，表型性状一般弱相关，这可能是由物种之间广泛的基因流或暴露于不同的选择压力。结论虽然两个约书亚树种产生不同的花香配置文件，这是不足以防止相关的传粉者的吸引力，以两个主机。相反，花的形态可能是介导物种间基因流动的关键性状。
PREMISE OF THE STUDY The role of floral scent in facilitating reproductive isolation between closely related plants remains poorly understood. Yucca brevifolia and Yucca jaegeriana are pollinated by different moth species in allopatry, but in a narrow contact zone, pollinator-host specificity breaks down, resulting in hybridization between species. We explored the chemical basis for reproductive isolation and hybridization in these Joshua trees by characterizing the floral scent of each species in allopatry, analyzing scent profiles from trees in the contact zone, and matching these data with genotypic and phenotypic data. METHODS We analyzed floral volatiles using gas chromatography-mass spectrometry, tested for species divergence of scent profiles and classified trees in the contact zone as hybrid or either parental species. We used floral and vegetative morphological data and genotypic data to classify trees and analyzed whether certain trait combinations were more correlated than others with respect to assignment of trees and whether frequencies of classified tree types differed depending on which data set was used. KEY RESULTS The Joshua tree floral scent included oxygenated 8-carbon compounds not reported for other yuccas. The two species differed (P < 0.001) in scent profiles. In the contact zone, many hybrids were found, and phenotypic traits were generally weakly correlated, which may be explained by extensive gene flow between species or by exposure to different selection pressures. CONCLUSIONS Although the two Joshua tree species produce distinct floral scent profiles, it is insufficient to prevent attraction of associated pollinators to both hosts. Instead, floral morphology may be the key trait mediating gene flow between species.