FIGURE 3.14 Body sizes of species on continental and high vs. low islands from the IOC to the CP. (H) and (L) refer to high and low island environments. Regional abbreviations are as in Fig. 3.6. Data for each species represent maximal recorded body length; plots for median body length provide a very similar pattern. Squares with crossbars are means.

ing the difficulty of establishing successful populations in these low-productivity environments that are heavily dominated by top predators (M.L.R., personal observation). We have observed one instance of population extinction in a small-sized reef stomatopod from a mid-Pacific atoll (Reaka and Manning, 1987b). Consequently, the wheels of speciation and extinction turn rapidly, but in reverse direction. If species arrive, speciation is high but extinction even higher; thus, diversity is low in remote oceanic regions of the IO and CP. Although the available evidence from life histories, geographic ranges, and extinction/speciation in stomatopods and other organisms supports this interpretation, molecular evidence on ages of species also is needed.

We conclude that life history patterns and dispersal are the primary mediators of the rate and direction of the speciation/extinction cycle, which in turn determines the geography of diversity and endemism. However, productivity, historical factors (antecedent faunas), and currents likely influence diversity in particular localities. In addition, productivity, historical factors (lineage history), and species diversity itself (through ecological interactions) alter body size and thus influence life history and dispersal.

We thank F. J. Ayala and J. C. Avise and two reviewers for helpful comments that improved the chapter.