Abstract
Recent worldwide taxonomical research on Cladocera is discovering a number of new species but hardly in South America. The Rio de La Plata is the second largest basin in the continent and the knowledge on cladocerans of the different sub-basins is uneven. The recent increase in the number of cladocerans species worldwide inspired this survey in the Rio de La Plata basin. It was expected that new species, or at least a significant number of new records, could be found which would contribute to the richness of the least studied sub-basins. Twenty three sampling locations were selected and the Cladocera were analyzed in detail to the species level. The family Chydoridae was targeted due to its high species richness. Fifty species of Chydoridae were recorded, two of them probably new for science and a third one whose taxonomical status could not be further addressed, due to insufficient material for analysis. All sub-basins had at least one specimen of one or both new species. The contribution of new species was more homogeneous among sub-basins when compared to the total contribution of new registers. It was concluded that the improvement of the taxonomical resolution and extensive samplings are fundamental in assessing the real cladoceran richness in the basin and that knowledge based on just a few research centers is not enough to promote secure taxonomical and biogeographical considerations yet.
Highlights
Research on cladoceran taxonomy is being carried out all around the world
Many of these centers are in the Río de La Plata basin, the second largest basin in South America and densely populated
Cladocerans were sampled with plankton net (68 μm), in 23 macrophyte-rich sites of the Río de La Plata basin during summer and winter 2010 (Fig. 1)
Summary
Cladocera investigation in South America and some other continents (Chatterjee et al, 2013) has historically focused on the ecology of the group, rather than on taxonomical investigation Due to this bias, contemporary research that applies a higher level of resolution for the taxa identification is frustrating as there are inconsistencies and many unidentified species. There is a historical lack of taxonomical knowledge, and a marked heterogeneity in the geographical distribution of the studies, which are concentrated around scientific centers. Many of these centers are in the Río de La Plata basin, the second largest basin in South America and densely populated. It is possible to find relatively well studied regions, such as the middle Paraná River sub-basin (e.g. José de Paggi and Paggi, 2007), and almost unstudied regions as the Paraguay River sub-basin, directly connected to the Pantanal, an extensive wetlandfloodplain system
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