Dispersal versus local recruitment - the central role of seed banks for meta-populaton dynamics in an aquatic plant

Abstract Progressive habitat fragmentation threatens plant species with narrow habitat requirements. While local environmental conditions define population growth rates and recruitment success at the patch level, dispersal is critical for population viability at the landscape scale. Identifying the dynamics of plant meta-populations is often confounded by the uncertainty about dormant population compartments. We combined a landscape-scale assessment of an amphiphytic species’ population structure with measurements of dispersal complexity in time to track dispersal and putative shifts in functional connectivity. Using 13 microsatellite markers, we analyzed the genetic structure of extant Oenanthe aquatica populations and their soil seed banks in a kettle hole system to uncover hidden connectivity among populations in time and space. Considerable spatial genetic structure and isolation-by-distance (IBD) patterns suggest limited gene flow between sites. Spatial isolation and size of patches showed minor effects on genetic diversity. Local recruitment was prevalent, despite some evidence for spatial migration and recent colonization. Our findings uncover stepping-stone dynamics with source-sink effects based primarily on dispersal from persistent local to adjacent populations. Overall, spatiotemporal connectivity patterns provide support for meta-population dynamics in our system and highlight the importance of persistent seed banks as a long-term source of genetic diversity.