Climate and habitat type interact to influence contemporary dispersal potential in Prairie Smoke (Geum triflorum)

Understanding dispersal potential, or the probability a species will move a given distance, under different environmental conditions is essential to predicting species' ability to move across the landscape and track shifting ecological niches. Two important drivers of dispersal ability are climatic differences and variations in local habitat type. Despite the likelihood these global drivers act simultaneously on plant populations, and thus dispersal potential is likely to change as a result, their combined effects on dispersal are rarely examined. To understand the effect of climate and varying habitat types on dispersal potential, we studied Geum triflorum-a perennial grassland species that spans a wide range of environments, including both prairie and alvar habitats. We explored how the climate of the growing season and habitat type (prairie vs. alvar) interact to alter dispersal potential. We found a consistent interactive effect of climate and habitat type on dispersal potential. Across prairie populations, an increased number of growing degree days favored traits that increase dispersal potential or the probability of dispersing farther distances. However, for alvar populations, dispersal potential tended to decrease as the number of growing degree days increased. Our findings suggest that under continued warming, populations in prairie habitats will benefit from increased gene flow, while alvar populations will become increasingly segregated, with reduced potential to track shifting fitness optima. We explored how the dispersal traits of Geum triflourm (Prairie Smoke), a perennial herb, changed with habitat type and climate. In isolated alvar habitats, G. triflorum seeds tend to disperse longer distances under shorter growing seasons and shorter distances under longer growing seasons. We found the reverse was true when G. triflorum was growing in continuous prairie populations. This was true for both (a) equal wind conditions and (b) when wind in prairies was increased relative to alvars.image