Aridification as a driver of biodiversity: a case study for the cycad genus Dioon (Zamiaceae)
Aridification as a driver of biodiversity: a case study for the cycad genus Dioon (Zamiaceae)
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DOI：
10.1093/aob/mcx123
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发表时间：
2018-01-01
期刊：
影响因子：
4.2
通讯作者：
Kajita, Tadashi
中科院分区：
文献类型：
--
作者：
Gutierrez-Ortega, Jose Said;Yamamoto, Takashi;Kajita, Tadashi
干旱化被认为是一种可能影响植物多样化的选择压力。据认为，植物适应干旱多样化的中新世，一个时代的全球干旱化（约1500万年前）。然而，证据支持多样化是干旱的直接反应是稀缺的，多学科的证据，除了只是系统发育的估计，是必要的，以支持干旱化驱动多样化的想法。苏铁属Dioon（Zamiaceae），一个热带类群，包括从潮湿森林到干旱地带发生的物种，被调查作为一个有前途的研究系统，以了解生境变化，多样化时间，叶表皮适应的进化，方法利用7个叶绿体DNA序列和ITS 2间隔区构建系统发育树，揭示14个Dioon属植物的亲缘关系从潮湿的森林到沙漠的栖息地。分歧的时间估计和整个Dioon的栖息地变化进行了检测。Dioon物种之间的表皮解剖进行了比较和相关性测试进行关联的表皮变化与栖息地parameters.Key结果事件的栖息地向干旱区转移只发生在Dioon的两个主要分支之一。这种栖息地的变化发生在Dioon的物种多样化，主要是在中新世。比较解剖表明，表皮的差异，从干旱和中温带栖息地的物种。表皮结构的变化与生境参数相关。此外，大多数分析的表皮性状表现出显着的系统发育signals.Conclusions Dioon的多样化已被驱动的干旱化的墨西哥。中新世的时间对应于嵌入祖先Dioon种群的干旱区的扩张。作为响应，在干旱区的物种进化表皮性状，以抵消干旱胁迫。这个案例研究提供了一个强有力的证据，支持干旱化是生物多样性的一个重要驱动力的想法。
Background and Aims Aridification is considered a selective pressure that might have influenced plant diversification. It is suggested that plants adapted to aridity diversified during the Miocene, an epoch of global aridification (approximate to 15 million years ago). However, evidence supporting diversification being a direct response to aridity is scarce, and multidisciplinary evidence, besides just phylogenetic estimations, is necessary to support the idea that aridification has driven diversification. The cycad genus Dioon (Zamiaceae), a tropical group including species occurring from humid forests to arid zones, was investigated as a promising study system to understand the associations among habitat shifts, diversification times, the evolution of leaf epidermal adaptations, and aridification of Mexico.Methods A phylogenetic tree was constructed from seven chloroplast DNA sequences and the ITS2 spacer to reveal the relationships among 14 Dioon species from habitats ranging from humid forests to deserts. Divergence times were estimated and the habitat shifts throughout Dioon phylogeny were detected. The epidermal anatomy among Dioon species was compared and correlation tests were performed to associate the epidermal variations with habitat parameters.Key Results Events of habitat shifts towards arid zones happened exclusively in one of the two main clades of Dioon. Such habitat shifts happened during the species diversification of Dioon, mainly during the Miocene. Comparative anatomy showed epidermal differences between species from arid and mesic habitats. The variation of epidermal structures was found to be correlated with habitat parameters. Also, most of the analysed epidermal traits showed significant phylogenetic signals.Conclusions The diversification of Dioon has been driven by the aridification of Mexico. The Miocene timing corresponds to the expansion of arid zones that embedded the ancestral Dioon populations. As response, species in arid zones evolved epidermal traits to counteract aridity stress. This case study provides a robust body of evidence supporting the idea that aridification is an important driver of biodiversity.