Pleurocarpous mosses diversification

The undoubted pleurocarps, however, are almost absent or at least extremely rare in earlier deposits. This fact, along with the other evidence, leads to the tentative conclusion (e.g.. Buck, 1991), that the evolution of pleurocarps followed the habitat diversification of the angiosperms, i.e., occurred in the Cretaceous. At the same time, an analysis of fossil data lead Krassilov and Schuster (1984) to the conclusion that the pleurocarpous mosses appeared no earlier than the Jurassic. 

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 diversification events. 

The LTT plot (Figure 17.2) allows comparison of the pattern of diversification of extant taxa in the pleurocarpous mosses with the equivalent curves for the angiosperms and polypod ferns as calculated by Schneider et al. (2004). Note that the shape of these plots is susceptible to differences in the sampling strategy (Nee et al., 1994 Pybus and Harvey, 2(XX) Shaw et al., 2003). Issues of systematic sampling bias were not explored by Shaw et al. (2003), who concentrated instead on the effect of randomized incomplete sampling, allowing them to accept or reject different models of diversification rates. 

It must also be noted that, if the fossil record accurately reflects the diversity of terrestrial ecosystems, the dense, complex angiosperm forests that we currently know, with their rich diversity of habitats, would have appeared relatively late in the process of diversification of angiosperm lineages (Behrensmeyer, 1992) further emphasizing the uncoupling of pleurocarpous moss diversification from... 

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