Environmental stability is low where polychaete species diversity is high: quantifying tropical vs temperate within-habitat features

Environmental harshness and stability were correlated with species diversity of tropical (Red Sea) vs temperate (Mediterranean) cryptofaunal polychaete communities, inhabiting interstices of biogenic, intertidal wave-exposed vermetid reefs. The tropical community is affected by harsher and less predictable exposure to air and to storms than the temperate community. Sea-surface temperatures, that have also regional, between-habit effects, are more benign and less seasonal in the Red Sea. Habitat-related differences in environmental harshness and stability, combined with region-related differences in the size of the species pool and possibly also in life-histories, may explain the observed higher within-habitat species diversity in the Red Sea, as accounted for by the dynamic competitive equilibrium model. This is provided that in the Red Sea vermetid reef, relative to the Mediterranean one, population reductions of polychaetes caused by environmental disturbances are more frequent, and populations' growth rates are slower, such that competitive displacements are rare. -Authors