Diversity and geographic distribution of free-living heterotrophic flagellates

Abstract

We have reviewed information from over 350 publications on marine heterotrophic flagellates. About 700 species and 214 genera have been reported. About 47 % of the 700 species have been reported from the original surveys from 41 marine habitats by the Protsville group of workers. The literature and the original surveys reveal that the majority of species have been reported from one site or one zone. This may be taken as an indication for endemism. However it is likely that this insight could be flawed by a variety of extrinsic factors. The most substantial of these factors is likely to be under-sampling and under-reporting of taxa from many sites and locations. In support of this, about 220 species were occurred in marine sediments, but fewer than 30 % of this number were reported from any one site of the sediments. We have argued above that as most surveys were considerably less intense than the one reported in this study, these low numbers most likely reflect under-reporting. Cumulative species curves for the numbers of species recorded showed that less than 50 % of the total number of species was encountered on the first sampling occasion, suggesting that lack of replication may also under-report the number of species. About 40 % of the species recorded in Botany Bay were encountered on 10 % or more of the sampling occasions. The remaining species can then be considered as rare, and likely not to be encountered in quick surveys. It suggests that the insights from the literature and original surveys are most likely caused by under-reporting and under-sampling, and until the species lists are more comprehensive, no firm conclusions should be drawn from these comparisons. As both of these extrinsic factors are corrected, the case for cosmopolitanism may be strengthened. By adopting a different strategy of analysing the similarities of communities from 40 surveys using the cluster algorithm in the PRIMER package, no evidence could be found that geograp