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The role of hydroperiod as an environmental filter in structuring wetland assemblages is usually associated with trait selection in invertebrates. However, the effects of changes in the hydroperiod of non-permanent wetlands on invertebrate assemblages are still unclear, and few studies have assessed the functional structure of insect assemblages along the hydroperiod gradient. In this study, we investigated the effects of different hydroperiod lengths on the functional structure of Odonata assemblages in non-permanent wetlands (posteriorly classified as 'short-', 'medium-' and 'long-hydroperiod') in southern Brazil in 2013 and 2014. Biological traits related to life-history strategies in temporary waters were assessed according to seasonal patterns of occurrence of nymphal and adult stages of odonates. Following the rationale of an environmental filter produced by hydroperiod, we expected to find (1) higher functional diversity in longer hydroperiods and (2) trait-convergence patterns in odonate assemblages in shorter hydroperiods. Patterns of functional diversity were detected along the hydroperiod gradient. More specifically, higher functional dispersion was found in long-hydroperiod wetlands and trait-convergence patterns occurred in wetlands with shorter hydroperiods, supporting our general hypothesis. Odonate taxa with life-history traits associated with shorter life cycles predominated in medium- and short-hydroperiod wetlands. Our results thus suggest that more pronounced reductions in wetland hydroperiod length should produce odonate assemblages functionally more similar, and these results gain special importance as climate change scenarios indicate that the hydrology of wetlands will be affected by variation in rainfall regimes.