Maintenance of soil ecotypes of Solidago virgaurea in close parapatry via divergent flowering time and selection against immigrants

1. The often patchy distribution of serpentine geology can lead to abrupt changes in soil and microclimates. Thus, serpentine areas provide an ideal natural laboratory to understand how divergent selection drives the process of local adaptation in edaphically endemic plant species. In case where the serpentine ecotype is surrounded by related non-soil specialists, a balance of natural selection and potential gene flow should be a key factor to maintain the different ecotypes over very short distances. We aimed to reveal the mechanisms to enable soil ecotypes of a goldenrod species to occur almost sympatric situations in Japan.
2. We performed field surveys to characterize microenvironments and reproductive timings of each ecotype, common garden and reciprocal transplant experiments, artificial crossing, and population genetic analysis.
3. Growth chamber experiments show that serpentine plants showed higher leaf mass per area and greater resource allocation to their root systems than d...