Current and Cretaceous-Cenozoic diversification of Angiosperms
  Cretaceous-Cenozoic history of angiosperms led to the a certain character of the distribution of taxa of different levels (the number of species and genera in families, species/genera ratio in families, the number of species in the genera). In most cases, these distributions are satisfactorily described by a power law (Pareto distribution). In logarithmic coordinates power function is a straight line. Empirical curves repeat this line is good enough, but on the right side of the graph (at low volumes taxa), there is a marked deviation of theoretical from the empirical curves. This suggests that the small volumes of taxa should be greater for full compliance with the theoretical curves. Modeling ratios among genera and species in families showed that only in the case of dynamic extinction factor observed satisfactory agreement between observed and calculated the number of species in a wide range of iterations. This suggested that there was a differential extinction of species during the evolution of angiosperms. This implies that the rate of extinction had to be minimal in genera with a large number of species. On the contrary, extinction rates may be increased by orders of magnitude with a decrease in the number of species. As a result, large genera became getting bigger and small genera become less. The species frequencies of distribution in the genera varied according to a power law. The initial divergence of taxa volume, which led to their further division into large and small, could be caused by the emergence and expansion of herbs with their functional and adaptive capabilities. 
Serge Sheremet'ev, Xenia Chebotareva
q-bio.PE