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Diversification of land plants: insights from a family-level phylogenetic analysis

DOI: 10.1186/1471-2148-11-341

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We 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.This 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.It is believed that climate change is one of the main factors affecting global biodiversity [1-3]. 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. Here we focus on land plants. The origin and diversification of land plants has intrigued biologists for centuries. 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]. These are liverworts (74 families, ca. 6,000 spp. [7]), mosses (112 families, ca. 12,000 spp. [8,9]), hornworts (five families, ca. 150 spp. [10]) and tracheophytes. The latter include ferns (45 families, ca. 9,000 spp. [11]), lycophytes (three families, ca. 1,200 spp. [12]), and seed plants, which in turn are separated into gymnosperms (14 families, ca. 1,000 spp. [13]) and angiosperms (456 families, ca. 260,000 spp. [13]).There are various possible scenarios to describe the processes that influenced land plant diversification throughout geological time. One frequently proposed scenario is based on a successive replacement of ancestral lineages by more derived lineages, which


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