Coastal environments encompass a number of unique stressors for terrestrial plant species, including reduced water availability due to the drainage properties of sandy soils. Such coastal stressors might lead to genetically based local adaptation in beach populations. To look for evidence of such adaptation, I compared Arabidopsis thaliana accessions sampled from beach populations to accessions from inland sites under treatments intended to mimic potential beach water availability regimes. Plants sampled from four source substrates (coarse beach sand, fine beach sand, inland sand, and inland soil) were grown on soil in the greenhouse in control, mild drought, and harsh drought treatment groups. Number of seeds produced was used as a proxy for total plant fitness.
Results/Conclusions
Overall, plants from non-soil substrates, especially coarse sand beaches, produced significantly less seed in greenhouse conditions. However, plants from non-soil substrates were also less affected by drought treatments. Mild drought treatment reduced seed production in plants from soil sites by about half, but did not reduce (and in some cases increased) seed production in plants from the other three substrate types. Harsh drought treatment significantly reduced seed production in plants from all substrate types, but had the largest effect on plants from soil sites. This significant treatment by source interaction effect suggests that plants from non-soil substrates may be locally adapted for tolerating reduced water availability.