Feild T S, Chatelet D S, Brodribb T J
Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, TN 37919 USA.
Geobiology. 2009 Mar;7(2):237-64. doi: 10.1111/j.1472-4669.2009.00189.x. Epub 2009 Feb 27.
Today, angiosperms are fundamental players in the diversity and biogeochemical functioning of the planet. Yet despite the omnipresence of angiosperms in today's ecosystems, the basic evolutionary understanding of how the earliest angiosperms functioned remains unknown. Here we synthesize ecophysiological, paleobotanical, paleoecological, and phylogenetic lines of evidence about early angiosperms and their environments. In doing so, we arrive at a hypothesis that early angiosperms evolved in evermoist tropical terrestrial habitats, where three of their emblematic innovations - including net-veined leaves, xylem vessels, and flowers - found ecophysiological advantages. However, the adaptation of early angiosperm ecophysiology to wet habitats did not initially promote massive diversification and ecological dominance. Instead, wet habitats were permissive for the ecological roothold of the clade, a critical phase of early diversification that entailed experimentation with a range of functional innovations in the leaves, wood, and flowers. Later, our results suggest that some of these innovations were co-opted gradually for new roles in the evolution of greater productivity and drought tolerance, which are characteristics seen across the vast majority of derived and ecologically dominant angiosperms today.
如今，被子植物是地球上生物多样性和生物地球化学功能的重要参与者。然而，尽管被子植物在当今生态系统中无处不在，但对于最早的被子植物如何发挥作用的基本进化理解仍然未知。在这里，我们综合了关于早期被子植物及其环境的生态生理学、古植物学、古生态学和系统发育学等方面的证据。通过这样做，我们得出一个假设：早期被子植物在终年湿润的热带陆地栖息地进化，在那里它们的三个标志性创新——包括网状叶脉、木质部导管和花朵——具有生态生理优势。然而，早期被子植物生态生理学对湿润栖息地的适应最初并没有促进大规模的多样化和生态优势。相反，湿润栖息地为该类群的生态立足提供了条件，这是早期多样化的一个关键阶段，需要在叶子、木材和花朵方面进行一系列功能创新的试验。后来，我们的研究结果表明，其中一些创新在提高生产力和耐旱性的进化过程中逐渐被用于新的用途，而这些特性在当今绝大多数衍生的和生态上占主导地位的被子植物中都能看到。
