These simulations assumed that all speciation events followed the "budding cladogenesis model" as referred to above and thus maximized the difference between ages of species.

Figure 1: The relationship between morphological variance and number of species for 95 passerine clades. The environmental template undoubtedly is clade-specific and difficult to evaluate ...

Microbiologists are challenged to explain the origins of enormous numbers of bacterial species worldwide. Contributing to this extreme diversity may be a simpler process of speciation in bacteria ...