Jodrell Laboratory, Comparative Plant and Fungal Biology Department, Royal Botanic Gardens Kew, Richmond, TW9 3DS, UK.
Laboratório de Sistemética Vegetal, Departamento de Botânica, Universidade de São Paulo, São Paulo, SP 05508- 090, Brazil.
New Phytol. 2019 Feb;221(3):1597-1608. doi: 10.1111/nph.15453. Epub 2018 Oct 4.
Changes in floral morphology are expected across evolutionary time and are often promoted as important drivers in angiosperm diversification. Such a statement, however, is in contrast to empirical observations of species-rich lineages that show apparent conservative floral morphologies even under strong selective pressure to change from their environments. Here, we provide quantitative evidence for prolific speciation despite uniform floral morphology in a tropical species-rich tree lineage. We analyse floral disparity in the environmental and phylogenetic context of Myrcia (Myrtaceae), one of the most diverse and abundant tree genera in Neotropical biomes. Variation in floral morphology among Myrcia clades is exceptionally low, even among distantly related species. Discrete floral specialisations do occur, but these are few, present low phylogenetic signal, have no strong correlation with abiotic factors, and do not affect overall macroevolutionary dynamics in the lineage. Results show that floral form and function may be conserved over large evolutionary time scales even in environments full of opportunities for ecological interactions and niche specialisation. Species accumulation in diverse lineages with uniform flowers apparently does not result from shifts in pollination strategies, but from speciation mechanisms that involve other, nonfloral plant traits.
花部形态的变化在进化时间上是可以预期的，通常被认为是被子植物多样化的重要驱动因素。然而，这种说法与物种丰富的谱系的经验观察结果相矛盾，这些谱系在强烈的环境选择压力下，其花部形态表现出明显的保守性。在这里，我们提供了定量证据，证明在热带物种丰富的树种谱系中，尽管花部形态一致，但仍存在大量的物种形成。我们在环境和系统发育背景下分析了桃金娘科（Myrtaceae）的花部差异，桃金娘科是新热带生物群中最多样化和最丰富的树种之一。在 Myrcia 进化枝中，花部形态的变异非常低，即使是在亲缘关系较远的物种之间也是如此。离散的花部特化确实存在，但数量很少，系统发育信号较低，与非生物因素没有很强的相关性，也不会影响谱系的整体宏观进化动态。研究结果表明，即使在充满生态相互作用和生态位特化机会的环境中，花部形态和功能也可能在大的进化时间尺度上保持保守。具有一致花朵的多样化谱系中的物种积累显然不是由于传粉策略的转变，而是由于涉及其他非花部植物特征的物种形成机制。
