. "3 Patterns of Biodiversity and Endemism on Indo-West Pacific Coral Reefs--MARJORIE L. REAKA, PAULA J. RODGERS, and ALEXEI U. KUDLA." In the Light of Evolution, Volume II: Biodiversity and Extinction. Washington, DC: The National Academies Press, 2008.
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In the Light of Evolution: Volume II—Biodiversity and Extinction
Meyer, 2003; Meyer et al., 2005). In addition to the fact that most benthic reef species are small in body size (Reaka-Kudla, 1997; Bouchet et al., 2002; Meyer et al., 2005) with restricted or moderate colonizing ability, the behavior of reef larvae further reduces dispersal. Stomatopod larvae (and those of most other reef taxa) exhibit diurnal vertical migrations, hiding in reef rubble by day and migrating into the water column at dusk and dawn (Robichaux et al., 1981), which reduces exposure to currents. Although panda clownfish have a 9- to 12-day pelagic phase, one-third of marked juveniles settle within their natal area, many within 100 m of their birth site (GP Jones et al., 2005).
Using body size as an indicator of speciation and extinction rates, we infer that the IAA, and to a lesser extent the IOC, are areas of both high origination and high extinction in reef stomatopods. However, rates of origination must exceed those of extinction in these areas, yielding the high biodiversity observed. Endemism results from either newly originated or almost extinct species and thus is expected to be especially high if both speciation and extinction are elevated, as is observed. Although species are concentrated in small size classes in the IAA and IOC, the range of body sizes is large in these areas (see Fig. 3.14). Historical factors (faunal carryover from the Tethys Seaway), productivity in the continental areas, currents, and species diversity itself (via ecological interactions between species) likely have contributed to the species richness and range of body sizes in the IOC and IAA. The dispersal and colonizing capability of large-sized species in these areas allows them to disproportionally colonize adjacent oceanic regions, where extensive larval immigration lowers extinction and retards speciation, yielding moderately diverse, somewhat larger-sized assemblages with low endemism.
In the center of the IO and in the broader expanse of the Pacific, however, larval immigrants have been filtered by starvation, predation, and distance. Given enough time, it is likely that larvae from diversity centers reach mid-ocean islands. However, both diversity and adult body size of reef stomatopods decline in the mid-Pacific, and body size is smaller on mid-Pacific atolls than on high islands, suggesting that productivity of the island environment, as well as propagule pressure, influences successful colonization. Dwarfed by limited productivity, populations cannot produce sufficient propagules to reach another island archipelago and are unlikely to receive many immigrants from ancestral populations to the west. They diverge into new species; endemism increases toward the CP. However, extinction also must be exceedingly high in these small-sized peripheral species. Endemics are missing from atolls, probably reflect-