Limnetica 35

Comprehending functional traits is increasingly recognized as an important element in the investigation of community assembly. We hypothesized that the homogenization effect of floods will lead to trait convergence in flooding periods, while environmental isolation will lead to trait divergence in drought periods. Sampling was carried out during two hydrological periods between 2002 and 2011 in a floodplain lake. The traits considered were taxonomical grouping, origin of the shell material, and presence of gas vacuoles. A functional dispersion index was calculated to detect trait convergence or divergence related to the hydrological periods over time. A redundancy analysis was carried out to investigate how the functional traits of the testate amoebae were linked to environmental variables during the different hydrological periods. We recorded seventy-nine taxa belonging to eight families. The functional index of testate amoebae indicated a predominant pattern of trait convergence in flooding and trait divergence in drought. Our results indicated that hydrological periods influence the functional traits of testate amoebae (indicating those typical of drought and flooding periods), which are strongly influenced by environmental variables related to food resources, especially chlorophyll a.