Co-occurrence patterns in invaded communities: what drives the spatial distribution of native and non-native species?

Abstract

Invaded communities were evaluated under two contexts: 1) how native communities respond to massive introduction events and 2) how invaded communities change through time. A common topic was defined to represent the modifications in communities after invasion, the co-occurrence between species. The objective of this thesis was to answer three questions: 1) whether the impact caused by non-native species is determined by the level of similarity between native and non-native species; 2) whether the impact would have the same pattern through time; and 3) whether there is any attribute of the non-native species population that determines the level of the impact. The data set from the project Pesquisas Ecológicas de Longa Duração (PELD) performed at the Upper Paraná River floodplain (Sítio PELD/PIAP) was used to answer these questions.First, it was evaluated the non-native species effects on the co-occurrence between species after the invasion of more than 30 non-native fish species at once. It was tested if the functional dissimilarity between native and non-native species drives the co-occurrence patterns between them. After, it was estimated the co-occurrence in a time series of 30 years. The non-native species evaluated were introduced by several introduction vectors. It was tested if the non-native species abundance and time since introduction drive the co-occurrence between native and non-native species. The abundance was used as the attribute of non-native species population to test if the effect of abundance is mediated by the phylogenetic distance between species. The results found showed that the co-occurrence between native and non-native species is affected by functional and phylogenetic distance. Therefore, integrating functional and phylogenetic diversity to assess the spatial distribution of organisms has potential to improve the understanding of co-occurrence patterns between native and non-native species. The results also showed that co-occurrence patterns may be more sensitive to the temporal variability in non-native population attributes (i.e. abundance) than time since introduction. It was showed that evaluating patterns of several non-native species may provide a broader understating of the entire community after invasions.