Origin and evolution of Petrocosmea (Gesneriaceae) inferred from both DNA sequence and novel findings in morphology with a test of morphology-based hypotheses.
Origin and evolution of Petrocosmea (Gesneriaceae) inferred from both DNA sequence and novel findings in morphology with a test of morphology-based hypotheses.
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通过基于形态学的假设检验，从 DNA 序列和形态学的新发现推断出 Petrocosmea（苦苣苔科）的起源和进化
DOI：
10.1186/s12870-015-0540-3
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发表时间：
2015-07-03
影响因子：
5.3
通讯作者：
Wang YZ
中科院分区：
文献类型：
--
作者：
Qiu ZJ;Lu YX;Li CQ;Dong Y;Smith JF;Wang YZ
背景：苦苣苔科石蝴蝶属（Petrocosmea奥利弗）目前包括38种和4个无名变种，几乎所有这些都是单独从植物标本馆标本中描述的。然而，干燥的标本掩盖了该属中存在的各种各样的形态变异，并导致了一个不反映该组进化历史的不良亚属分类系统。因此，发展新的形态学研究方法，发现新的形态学性状，并在新的假设基础上重新审视和评价传统形态学数据，具有重要意义。此外，石蝴蝶属是一个中等大小的属，但表现出极端多样的花变种。这使得该属特别感兴趣的问题，是否有任何关键因素，是专门与他们的进化和diversification.Results：在这里，我们提出了第一个系统发育分析的属密集的分类采样和多个基因相结合的综合形态调查。最大简约，最大似然和贝叶斯分析的分子数据，从两个核DNA和6个叶绿体DNA区域支持单系性的石蝴蝶属，并恢复5个主要分支内的属，这是有力地证实了重建的祖先状态的12个新的形态特征直接观察到的生活材料。祖先区域重建表明，其最共同的祖先可能位于喜马拉雅-青藏高原的东部和东南部。石蝴蝶属的起源可能涉及一系列的形态学变化，从具茎到无茎的习性，以及从长花冠筒的四雄蕊花到短花冠筒的二雄蕊花，在分支A中的退化的具茎习性和过渡的花形式也很明显，分支A是该属其余部分的姐妹。在石蝴蝶属的5个分支中，花的形态分化模式与不连续的谱系相关的形态型一致，这是对交替环境的一种重复的适应性反应。结论：我们的研究结果表明，反映在上唇（昆虫授粉的功能器官）上的谱系特异性形态分化可能是对传粉者转移的适应性反应。我们进一步认识到，石蝴蝶属植物花部形态的多样性涉及到几种进化现象，即进化的连续特化、逆转、平行进化和趋同进化，这可能与喜马拉雅-青藏高原东翼地区异质的生物和非生物环境背景下对传粉的适应有关。
Background:Petrocosmea Oliver (Gesneriaceae) currently comprises 38 species with four non-nominate varieties, nearly all of which have been described solely from herbarium specimens. However, the dried specimens have obscured the full range of extremely diverse morphological variation that exists in the genus and has resulted in a poor subgeneric classification system that does not reflect the evolutionary history of this group. It is important to develop innovative methods to find new morphological traits and reexamine and reevaluate the traditionally used morphological data based on new hypothesis. In addition, Petrocosmea is a mid-sized genus but exhibits extreme diverse floral variants. This makes the genus of particular interest in addressing the question whether there are any key factors that is specifically associated with their evolution and diversification.Results:Here we present the first phylogenetic analyses of the genus based on dense taxonomic sampling and multiple genes combined with a comprehensive morphological investigation. Maximum-parsimony, maximum likelihood and Bayesian analyses of molecular data from two nuclear DNA and six cpDNA regions support the monophyly of Petrocosmea and recover five major clades within the genus, which is strongly corroborated by the reconstruction of ancestral states for twelve new morphological characters directly observed from living material. Ancestral area reconstruction shows that its most common ancestor was likely located east and southeast of the Himalaya-Tibetan plateau. The origin of Petrocosmea from a potentially Raphiocarpus-like ancestor might have involved a series of morphological modifications from caulescent to acaulescent habit as well as from a tetrandrous flower with a long corolla-tube to a diandrous flower with a short corolla-tube, also evident in the vestigial caulescent habit and transitional floral form in clade A that is sister to the remainder of the genus. Among the five clades in Petrocosmea, the patterns of floral morphological differentiation are consistent with discontinuous lineage-associated morphotypes as a repeated adaptive response to alternative environments.Conclusion:Our results suggest that the lineage-specific morphological differentiations reflected in the upper lip, a functional organ for insect pollination, are likely adaptive responses to pollinator shifts. We further recognize that the floral morphological diversification in Petrocosmea involves several evolutionary phenomena, i.e. evolutionary successive specialization, reversals, parallel evolution, and convergent evolution, which are probably associated with adaptation to pollination against the background of heterogeneous abiotic and biotic environments in the eastern wing regions of Himalaya-Tibetan plateau.