Data for: Invasion by an exotic grass species homogenises native freshwater plant communities

A growing body of evidence has shown that biological invasions cause shifts in species composition of communities in space and time. Although biological invasions are considered a major driver of biotic homogenisation worldwide, most previous studies are conducted at small spatial scales and over short time periods, which may have underestimated the impacts of exotic species on native communities.
Using a unique dataset of aquatic plants sampled in 235 sites over 12 years (2007–2010 and 2015–2019) in a large reservoir (Itaipu Reservoir; 1,350 km²), we analyzed how the invasion of a non-native grass (Urochloa arrecta) affects the species richness, ecological uniqueness (i.e., local contribution to beta diversity – LCBD) and temporal β–diversity of native plant communities.
From 3,934 surveyed plant communities, U. arrecta was recorded in 2,888 samples and it was absent from 1,046 samples. Overall, species richness and ecological uniqueness of native plant communities were markedly lower ..., We analysed a 12-years data set (2007–2010 and 2015–2019) with presence-absence data for aquatic plants recorded in the Brazilian shoreline of the Itaipu Reservoir, a large water body filled in 1982 and located in the frontier between Brazil and Paraguay (24º15’–25º33’ S and 54º00’–54º37’ W; Figure 1). This reservoir covers an area of 1,350 km², has a mean depth of 22 m and its arms (the sampled sites) vary from oligotrophic to eutrophic (Thomaz et al., 2009). The local mean annual temperature is 22 ºC and the mean annual rainfall is 1,400 mm. More detailed information on environmental data can be found in Thomaz et al. (2003) and Pulzatto et al. (2019). It is not certain when U. arrecta first colonized this reservoir, but this species has been recorded since the first sampling carried out in Itaipu in 1996 (S. M. Thomaz, unpublished).
            We used aquatic plant data collected between 2007 and 2010 as well as between 2015 and 2019 in 235 sites located in the Reservoir arms, total...,