ECOLOGICAL BIODIVERSITY OF MARINE NEMATODES IN SAMPLES FROM TEMPERATE, TROPICAL, AND DEEP-SEA REGIONS

Little is known about the biodiversity of free-living nematodes. We ha ve attempted to provide baseline information about the natural diversi ties (those not influenced by pollution) that might be expected in six biotopes. Seventeen marine nematode data sets consisting of 197 sampl es were standardized to allow a comparison of alpha diversity, or samp le diversity, from temperature estuarine, tropical sublittoral, temper ate sublittoral, bathyal, abyssal, and hadal biotopes, which were sele cted on criteria of depth and latitude. The diversity analysis methods we employed were rarefaction curves; three weighted diversity indices of species richness, SR, H' and ES(X); and two equitability indices, J' and V. Diversity was significantly different In the six biotopes. T he weighted indices of species richness were more capable of resolving differences between the biotopes than were the equitability indices, whose large standard errors suggested that they were more influenced b y local, small-scale ecological factors. This suggests that species ri chness is a better measure than equitability for large-scale compariso ns of biotopes or regions. The ES(X), which is robust to sample size v ariations, was more efficient than the weighted indices of species ric hness, which were easily influenced by sample size. There was a nonlin ear relationship between depth and diversity with the bathyal and abys sal biotopes displaying the highest diversity. The tropical sublittora l biotope was not more diverse than the temperate sublittoral biotope. The lowest diversifies were found in the physically challenging tempe rate estuarine and hadal biotopes.