River regulation has altered hydrological connectivity characteristics throughout the Murray-Darling Basin. These alterations are likely to have affected the hydrochory (water dispersal) patterns for many plant species. It has been hypothesised that increased connectivity leads to the homogenisation of aquatic and floodplain plant assemblages by facilitating the dispersal of propagules. Equally it has also been suggested that decreased connectivity may homogenise assemblages by reducing the spatial and temporal diversity of habitats. We looked at the effects of decreased and increased connectivity on presence/absence of plant species from wetland and floodplain sites obtained from seven geographically separated locations in the southern MDB (Barmah Forest, Gunbower Forest, Hattah Lakes, Great Darling Anabranch, Lindsay-Mulcra-Wallpolla Island, Chowilla Floodplain and the Lower Lakes). We compared the composition of aquatic and floodplain plant communities both within and between locations during low connectivity (the recent drought, 2000-10) and increased connectivity (post the 2010-11 floods).

Analysis of the data indicated a high degree of uniqueness of plant species to individual sites within locations during both low and increased hydrological connectivity.  Multivariate analysis demonstrated that at all locations community composition differed between periods of low and increased connectivity and that locations were distinct to each other. However, in rejection of our hypothesis, there was no consistent trend in increased or decreased homogeneity of plant assemblages with increased connectivity. Our results indicate that the observed heterogeneity of floodplain and wetland plant communities across both periods of connectivity is influenced by local factors within sites and /or dispersal limitations between sites.