Functional dissimilarity correlates to the co-occurrence patterns of native and non-native species

Many theories have been created to explain the mechanisms driving species coexistence. They are mainly based on biotic interactions and abiotic factors, which are being constantly affected by human activities. In invaded communities, novel ecological interactions among organisms are created and native and non-native species have to coexist. This coexistence can be supported by different interactions (both positive and negative) and, in some cases, can be followed by negative impacts on the spatial distribution of native species. We aimed to assess the role of the functional differences and species status influencing co-occurrence patterns between native and non-native species at the Upper Paraná River floodplain, Southern Brazil. We estimated the co-occurrence between pairs of native and non-native species and their functional dissimilarity using morphological traits. We found a positive relationship between co-occurrence and functional dissimilarity between species: more similar native and non-native species tended to co-occur less. The co-occurrence was also related to species status: it was higher between pairs of native species than between pairs of native and non-native species. Niche differentiation may play an important role in driving the observed co-occurrence patterns at small spatial scales. However, this can lead to a limitation on the space use of species and modifications in the taxonomic and functional diversity of the native community. Although we recognize that species coexistence may be driven by several factors, we show here that the co-occurrence patterns of native and non-native species were affected by their functional dissimilarity.