Dispersal is a key process that influences the geographic extent of species’ ranges. Species distribution models (SDMs) are commonly used to predict the future location of species’ ranges in response to land-use or climate change. However, SDMs commonly assume that all populations within species have equal dispersal kernels, despite evidence that dispersal traits can vary due to genetic or environmental differences among populations. We evaluate this assumption to understand the range dynamics of Cakile edentula var. lacustris (American searocket), an annual plant restricted to beaches of the Great Lakes in North America. This species has a dimorphic fruit that may generate a bimodal dispersal kernel: a proximal fruit segment that stays attached to the mother plant, and a distal fruit segment that disperses short, local distances via wind and long distances via water.
Results/Conclusions
We collected phenotypic data on dispersal traits from 30 sites across this species’ geographic range, and found a significant relationship between many dispersal traits and latitude. Common garden and greenhouse experiments indicate that a proportion of this variation is due to genetic differences among sites. These results indicate that dispersal traits vary significantly, and even predictably, across the range of this species, and we hypothesize that this variation may have major implications for range dynamics in response to climate change. To test this hypothesis, we are developing an individual-based, spatially explicit SDM that will incorporate latitudinal variation among populations in traits that influence local and long-distance dispersal.