Abstract
BackgroundSome of the evolutionary history of land plants has been documented based on the fossil record and a few broad-scale phylogenetic analyses, especially focusing on angiosperms and ferns. Here, we reconstructed phylogenetic relationships among all 706 families of land plants using molecular data. We dated the phylogeny using multiple fossils and a molecular clock technique. Applying various tests of diversification that take into account topology, branch length, numbers of extant species as well as extinction, we evaluated diversification rates through time. We also compared these diversification profiles against the distribution of the climate modes of the Phanerozoic.ResultsWe found evidence for the radiations of ferns and mosses in the shadow of angiosperms coinciding with the rather warm Cretaceous global climate. In contrast, gymnosperms and liverworts show a signature of declining diversification rates during geological time periods of cool global climate.ConclusionsThis broad-scale phylogenetic analysis helps to reveal the successive waves of diversification that made up the diversity of land plants we see today. Both warm temperatures and wet climate may have been necessary for the rise of the diversity under a successive lineage replacement scenario.
Highlights
Some of the evolutionary history of land plants has been documented based on the fossil record and a few broad-scale phylogenetic analyses, especially focusing on angiosperms and ferns
According to the fossil record, land plants diverged from green algae before 475 million years ago (Ma; first land plant fossil) and led to the major clades found today [5,6]
In this study we ask two questions: (1) Do we find evidence for non-constant rate of diversification in land plants? (2) Are major shifts of diversification rates, if any, correlated with some major external factors such as global climate warming or cooling?
Summary
Some of the evolutionary history of land plants has been documented based on the fossil record and a few broad-scale phylogenetic analyses, especially focusing on angiosperms and ferns. During the history of life, fluctuations of the world’s climate have most likely caused major extinctions [4] and led to the development of new ecosystems, promoting new biotic interactions and the evolution of novel adaptive traits. The dynamics of such diversification events can be studied based on phylogenetic trees dated with fossils. According to the fossil record, land plants diverged from green algae before 475 million years ago (Ma; first land plant fossil) and led to the major clades found today [5,6] The latter include ferns (45 families, ca. 9,000 spp. [11]), lycophytes (three families, ca. 1,200 spp. [12]), and seed plants, which in
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