*EASTBIO* Growing on the edge: The genomic basis of coastal adaptation in eyebrights (Euphrasia)

Local adaptation enables plant populations to survive in extremely harsh environments. Coastal habitats present a suite of challenging conditions with plants exposed to drying oceanic salt spray and osmotically stressful high salinity soils. Despite adaptation to saline environments being a ubiquitous feature of coastal plant populations, little is known about adaptation to these conditions. In particular, the genetic basis of salt tolerance has rarely been characterised in natural populations, and whether adaptation to coastal environments comes at a cost for colonising new (non-coastal) habitats is not known.

This project will use British native species of eyebrights to study adaptation to coastal environments. There are 21 native eyebright species, with taxa found in a wide range of environmental conditions. These species are a useful system for investigating coastal adaptation as populations are widespread along the coast and inland, these species are experimentally tractable and can be grown in common garden conditions and at field sites, and there are a range of genomic tools for linking phenotype to genotype. We test the hypothesis that as adaptation to coastal habitats is extremely common we expect it to involve the fixation of pre-existing (standing) genetic variation found in inland populations.

The core of the project will involve growing the coastal species E. tetraquetra, E. foulaensis, and E. marshallii, along with grassland species E. arctica and E. nemorosa, under experimental conditions where coastal stressors are simulated, and under benign conditions. This experiment will look at the phenotypic and transcriptomic (gene expression) changes associated with these environments. The research will also involve population genomic sequencing of pairs of coastal and inland plants to look at the extent of immigration between contrasting environments. Specifically, we will address the following research questions:

What is the extent of adaptation to coastal environments in populations of eyebrights?
What are the genome-wide expression changes in response to simulated coastal stressors?
Is selection acting against migrants into coastal habitats in the wild?

This project will involve research at the University of Edinburgh and at the Royal Botanic Garden Edinburgh. Primary activities will be growth experiments, molecular work, and bioinformatic analyses, with the potential for extensive field work across the UK.

Recommended reading:
Lowry DB, Hall MC, Salt DE, Willis JH (2009) Genetic and physiological basis of adaptive salt tolerance divergence between coastal and inland Mimulus guttatus. New phytologist 183, 776-788.
Twyford AD (2018) Parasitic plants. Current Biology 28, R857-R859.
Wang X, Gussarova G, Ruhsam M, de Vere N, Metherell C, Hollingsworth PM, Twyford AD (2018) DNA barcoding a taxonomically complex hemiparasitic genus reveals deep divergence between ploidy levels but lack of species-level resolution. AoB PLANTS 10, ply026-ply026.