Phenotypic variation and adaptation in morphology and salt spray tolerance in coastal and inland populations of Setaria viridis in central Japan

Abstract

AbstractVariations in morphology and salt spray tolerance were studied among 22 populations of Setaria viridis derived from the coastal and inland habitats of central Japan to elucidate the adaptation of the species to coastal habitats, which are important reservoirs that enhance the overall species diversity in agro‐ecosystems. The S. viridis populations comprised three ecotypes that differed in plant form and salt spray tolerance: coastal short, for populations within rocky cliffs and pebble shores; coastal tall, found in sandy shores; and ordinary inland tall ecotypes. The coastal short ecotype exhibited significantly higher salt spray tolerance than the ordinary inland ecotypes. The coastal tall ecotype found primarily within the Seto Inland Sea had intermediate salt spray tolerance. The compact stature and high salt spray tolerance of the coastal short ecotype appeared to be adaptive to intensive salt spray transported by strong winds from the open sea, whereas mild breezes off the Inland Sea enabled the tall and moderately tolerant plants to survive on the sandy shores. At Cape Naruto, both coastal short and inland tall ecotypes were observed separately in continuous plant sequences from rocky cliffs to inland areas. The inland tall ecotype that is susceptible to salt spray could survive within this area because the surrounding evergreen trees impede salt spray. The coastal short ecotype occupies rocky cliffs because migrants coming from inland could be eliminated by intensive salt spray. Therefore, maintaining the specific habitats to which coastal plants have fully adapted is highly important for the preservation of biodiversity.