Local-regional species richness relationships are linear at very small to large scales in west-central Pacific corals

If local communities are saturated with species, the relationship between local and regional species richness [the local species richness (LSR)-regional species richness (RSR) relationship] is predicted to become increasingly curvilinear at more local spatial scales. This study tested whether the LSR-RSR relationship for coral species was linear or curvilinear at three local scales across the west-central Pacific Ocean, along a regional biodiversity gradient that includes the world's most diverse coral assemblages. The local scales comprised transects 10(0-2) m apart, sites 10(3-4) m apart and islands 10(4-6) m apart. The LSR-RSR relationship was never significantly different from linear at any scale. When the Chao1 estimator was used to predict true RSR and LSR, all relationships were also strongly linear. We conclude that local assemblages are open to regional influences even when the local scale is very small relative to the regional scale, and even in extraordinarily rich regions.