Real Jardín Botánico de Madrid (RJB), CSIC, 28014, Madrid, Spain.
Biodiversity Research Centre, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada.
New Phytol. 2022 Jul;235(1):344-355. doi: 10.1111/nph.18100. Epub 2022 Apr 5.
Angiosperm lineages in aquatic environments are characterized by high structural and functional diversity, and wide distributions. A long-standing evolutionary riddle is what processes have caused the relatively low diversity of aquatic angiosperms compared to their terrestrial relatives. We use diversification and ancestral reconstruction models with a comprehensive > 10 000 genus angiosperm phylogeny to elucidate the macroevolutionary dynamics associated with transitions of terrestrial plants to water. Our study reveals that net diversification rates are significantly lower in aquatic than in terrestrial angiosperms due to lower speciation and higher extinction. Shifts from land to water started early in angiosperm evolution, but most events were concentrated during the last c. 25 million years. Reversals to a terrestrial habitat started only 40 million years ago, but occurred at much higher rates. Within aquatic angiosperms, the estimated pattern is one of gradual accumulation of lineages, and relatively low and constant diversification rates throughout the Cenozoic. Low diversification rates, together with infrequent water transitions, account for the low diversity of aquatic angiosperms today. The stressful conditions and small global surface of the aquatic habitat available for angiosperms are hypothesized to explain this pattern.
水生环境中的被子植物谱系以高度的结构和功能多样性以及广泛的分布为特征。一个长期存在的进化谜题是，与它们的陆生亲属相比，水生被子植物的多样性相对较低，是什么过程导致了这种情况。我们使用多样化和祖先重建模型，结合一个综合的> 10 000 属被子植物系统发育，阐明与陆生植物向水生环境过渡相关的宏观进化动态。我们的研究表明，由于较低的物种形成率和较高的灭绝率，水生被子植物的净多样化率明显低于陆生被子植物。从陆地到水的转变在被子植物进化的早期就开始了，但大多数事件集中在过去的大约 2500 万年。4000 万年前才开始向陆地栖息地的逆转，但发生的速度要高得多。在水生被子植物中，估计的模式是谱系的逐渐积累，以及整个新生代相对较低且稳定的多样化率。低多样化率，加上水生环境中可供被子植物利用的水栖息地的稀缺性，导致了水生被子植物今天的多样性较低。水生栖息地的压力条件和较小的全球表面被假设可以解释这种模式。
