Conclusions

This concluding chapter summarizes the book's major findings and presents some final thoughts. Among these findings is clear evidence that global biodiversity organizes into distinct patterns within four major biogeographic realms: coastal, pelagic, deep ocean, and land. Taxonomically distinct species groups tended to show similar patterns of biodiversity at large scales within each of these four realms. A body of theory was devised that might explain observed biodiversity patterns within and across taxa. This theory suggests that only two variables are required to predict the majority of first-order patterns of biodiversity on our planet: ambient temperature and community size. Temperature primarily affects the rate of community turnover and the speed of evolution, while community size determines the number of individuals on which evolutionary processes can act.