Much of the native Midwestern United States grasslands have been lost to agriculture and urban development. To combat this habitat loss, managers conduct grassland restorations that return converted lands back into natural habitat. Despite efforts, it is unclear whether local patches of grassland habitat maintain connectivity of both genes and species across the broader landscape. Current connectivity metrics for plant communities tend to use broad generalizations about dispersal ability, without considering the species and trait-level variance in movement ability. To begin to understand how well plant propagules (i.e. pollen grains and seeds) move in a spatially fragmented landscape, we first ask: under what conditions can remnant prairies serve as a high-diversity seed source for adjacent restored prairies? To answer this question, we survey plant cover along 120m transects between adjacent remnant and restored prairies. Then we broaden our research scope to ask: how likely is plant pollen to move between more distantly located landscape patches? To measure pollen dispersal ability, we use a molecular-based paternity approach and collect tissue from all possible pollen donors (male plants), and collect seeds from a subset of pollen acceptors (female plants) in a large, contiguous remnant prairie in NW Minnesota.
Results/Conclusions
To answer our first question, we found that remnant prairies can in fact serve as a seed source of diverse propagules into adjacent restored prairies, but only up to 50 meters, and only into low-diversity restored prairies (linear model results of source * distance * seeded diversity; F(7,64) = 5.718, p = 0.02). These results relate to classic community invasion theory, that generally shows highly diverse communities are more likely to resist invaders, however here our “invaders” are native species recolonizing previously unoccupied areas. In addition, there is likely a time aspect to this result, as the restored prairies with lower diversity were planted earlier (1980’s - 1990’s) than those planted with higher diversity (early 2000’s – present). Similar spatial re-invasion results could play out in the higher diversity sites over a longer period of time, as it might take longer to see these native species moving into more highly diverse restored prairies. To answer our second question, we are in the process of measuring the pollen dispersal ability of several species of grassland plants that vary in their pollen-dispersal vectors. Preliminary results lead us to believe the dispersal abilities will depend on the vector, and thus will vary across species.