The pleurocarpous mosses are a highly diverse monophyletic lineage, comprising about 42% of the approximately13,000 extant species of mosses. Phylogenetic analysis of molecular data suggests that the pleurocarps diversified over a (geologically) short period of time. The absence of a good fossil record has hindered attempts to determine when this group evolved and the processes implicated. In particular, the idea that evolution of pleurocarpous mosses was associated with the appearance of angiosperm forests has been untestable, and needs further study.
We explored the patterns of diversification of the pleurocarps and estimated possible dates for their origins. Phylogenetic analyses, using Bayesian inference procedures, were conducted using molecular gene sequence data from the plastid rps4 and rbcL genes sampled for 12 vascular plants, 2 hornworts, 34 hepatics and 103 mosses. Ages for well-supported nodes were estimated using penalized likelihood and calibrated on the fossil date of 450 myr for the origin of land plants.
The appearance of pleurocarpy was dated at 194–161 mya, significantly earlier than the radiation of the majority of pleurocarp lineages about 165–131 mya. This radiation coincides with the diversification of the angiosperms in the Early Cretaceous, but predates appearance of complex angiosperm forests in the early Cenozoic. The hypothesis that pleurocarpous mosses evolved to
exploit the angiosperm forests is modified — pleurocarpous mosses diversified in the same time frame as the early angiosperms and the recovered pattern suggests a putative correlation of these
CRC Press (Taylor & Francis Books, Inc) , 2006.