Morphometric and biotic variables as potential predictors of Ludwigia sedoides (Humb. & Bonpl.) Hara in a large

Abstract – Reservoirs cause hydrological changes (i.e., water level stabilization) that favor the colonization of aquatic macrophytes. Knowing the ecological factors that determine the occurrence of these plants is cri-tical for water management (e.g., plant control) and biodiversity conservation. In this sense, the present study investigated colonization patterns of Ludwigia sedoides in Lajeado reservoir (Tocantins River, Amazon Basin), in order to identify variables that influence colonization at habitat scale. We investigated the relation-ship between colonization (coverage area and occurrence) and morphometric (fetch, slope, depth and distance from shoreline) and biotic variables (local diversity of macrophytes and co-occurrence patterns). Stepwise re-gression selected fetch, depth and slope as the best variables to explain the variation in L. sedoides coverage, which together explained 46 % of data variability. Fetch and slope were negatively correlated with coverage, whereas depth showed a positive correlation. No biotic variable was included in the model (P>0.05). However, the investigation of the geometric shape of bivariate correlations (null models) showed positive relationships with local species richness and richness of life forms (i.e., submerged, emergent, floating and epiphytic). In addition, an analysis of species co-occurrence (C-score) revealed that L. sedoides is negatively associated with some macrophyte species. We believe, however, that these results may be associated with species preferences for particular environmental conditions. In conclusion, the present study indicated tha