Local adaptation and transplant dominance in genets of the marine clonal plant Zostera marina

Abstract

Worldwide decline of seagrass beds has increased the need for information on potential source populations for recolonization and conservation purposes. The aim of the present study was to test for local adaptation in Zostera marina, the dominant seagrass species of the northern hemisphere. To this end, we performed a reciprocal transplant experiment at the level of the genetic individual (= clone or genet) in 2 Baltic Sea populations for which the clonal structure had been mapped in detail. The treatment effects were tested on aboveground and belowground dry weight of physiologically independent rhizome fragments of replicated genets at the end of the season. We found that genets from both populations produced more biomass in their home population (local adaptation). Genets from 1 population produced more biomass overall (overall dominance) and the range of cross-site performance indicated a high degree of variability among genets within the 2 populations. Our results provide a first test for local adaptation in established seagrass genets and demonstrate home site advantage of clones that are part of a highly connected system of Z. marina populations along the Baltic Coast.