Success and impacts of the invasive plant, lesser celandine

Background/Question/Methods

Lesser celandine (Ranunculus ficaria), is an invasive plant that has become more widespread in river valleys in parts of the United. Its extensive monocultures are thought to harm native species, although evidence of direct impacts is limited. Its unusual reproductive output of asexually produced bulbils, as well as tubers and seeds, allows it to rapidly spread once present. In Northeast Ohio, we examined lesser celandine populations to determine what biotic and abiotic characteristics are associated with successful invasions and what native plants persist or are lost during R. ficaria invasion. R. ficaria abundance and reproductive outputs and site characteristics were quantified in plots in well-established populations spanning a disturbance gradient away from a river. Terminal restriction fragment length polymorphism and cloning were used in conjunction to determine the differences in the community composition of root-associated fungi. We also surveyed plant populations in areas with and without R. ficaria to quantify potential responses of the native community. We hypothesized that that R. ficaria performance would be driven mainly by soil characteristics, including endophytic root fungal communities. We further expected that native species richness would be higher in uninvaded areas, and sought to identify species that persisted despite high R. ficaria cover.

Results/Conclusions

There was high variability observed between sites; densities of R. ficaria were as high as 11,425 plants/m2 in some areas, with an overall mean of 2,772 plants/m2. There was considerable bulbil and tuber production, but we did not observe any seed production in our sample plots. Soil characteristics, rather than landscape placement, appeared to drive plant performance; lower percent sand was associated with significantly higher R. ficaria stem density (P=0.012), and bulbil (P=0.027) and tuber production (P=0.009). The presence of root-associated fungi was confirmed by microscopy, and sites with fungal communities containing dark septate endophytes and ericoid fungi had significantly higher average biomass (P=0.033) and bulbil counts (P=0.019) than sites with different soil fungal communities. Native species richness and percent cover was higher in uninvaded plots; nevertheless, there was still considerable native diversity present near even the most heavily invaded plots. Several other non-native species were also present in heavily invaded plots, such as Rosa multiflora and may also be playing a role in suppressing native species. These studies together help expand the current limited understanding of lesser celandine and can help identify where this species is most likely to be problematic.