Taxonomic sufficiency in detecting hydrological changes and reproducing ordination patterns: A test using planktonic ciliates

Ciliates are commonly and successfully used as bioindicators in marine ecosystems, even at low levels of taxonomic resolution. However, the use of these organisms in biomonitoring programs of freshwater ecosystems is less common. Evidence showing the reliability of the taxonomic sufficiency approach for freshwater ciliates is also limited. Demonstrating taxonomic sufficiency would be important to foster the use of ciliates in freshwater biomonitoring programs in a cost-effective way. Here we tested whether richness and multivariate patterns generated by ciliate community data, at species level, were retrieved by analyses carried out with data at lower taxonomic resolutions. Community and environmental datasets were gathered at 36 sites in the Upper Parana River floodplain (Brazil), during high and low water levels periods of the years 2010 and 2011. We found that, in comparison with species-level data, genus-level identification was sufficient to detect the effects of the environmental changes caused by floods, to retrieve the ordination patterns generated during each hydrological period and to detect relationships with environmental and spatial gradients. We also showed that the use of coarser taxonomic resolutions was not advisable because high relationships with species-level data were found only with genus-level data. We encourage the use of ciliates in biomonitoring programs of freshwater ecosystems and, according to our results, the use of genus-level identification is a reliable strategy, not only to increase cost efficiency, but also to guarantee temporal comparability of data.