Mechanisms of speciation

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The purpose of this study is to investigate the conditions that allows speciation that is the only source of species diversity of organisms. This study to scrutinize the speciation mechanisms is carried out by the theoretical studies and the empirical studies using fossil records and molecular phylogeny.Specifically, we build a basic individual-based model of sexual selection and studied the possibility and conditions of speciation. We examined how the likelihood of speciation depends on the distributions of a male sexual character and the associated female preference characters. We found that the frequency of speciation events increases with the overall variations in the male and female traits that depend on the duration of isolation of two conspecific populations. This indicates that the speciation events are not limited by ecological niche widths, rather it is unlimited due to the variation in mating preferences.This result suggests, that extraordinal species diversity seen in some communities, such as tropical forests and cichlid fishes in African lakes could be possible due to speciation by sexual selection.We carried out many extensions and related studies of biodiversity and mating behavior from the main project : (1) large-scale model of multiple speciations in relation to geographical spatial distributions and long-term environmental fluctuations (e.g., glacial periods), (2) the lattice model of stability and coexistence of many species (grassland community model) to evaluate the stability and coexistence of newly speciated species, (3) an individual-based mating behavior model of hilltopping behavior in insects and simulations, and (4) the quantitative analyses of stability and seasonality of animal sex ratios.