The behavior of the species of theRamalina siliquosa group in Portugal

Summary

Four of the six European species of the maritime rock-inhabitingR. siliquosa group occur in Portugal.Ramalina siliquosa (producing protocetraric acid) andR. curnowii (stictic acid) are very common there;R. druidarum (hypoprotocetraric acid), although locally abundant, is less frequent; andR. crassa (salazinic acid) is extremely rare. As it does in northern Europe,R. curnowii inhabits the most exposed situations, those subjected to the harshest environmental conditions, whileR. siliquosa and especiallyR. druidarum completely dominate the more sheltered habitats and those at some distance from the sea altogether. The ecological sensitivity of the species of theR. siliquosa group is so great that it appears that surfaces of various exposures on boulders as small as three meters high may supportRamalina vegetations of substantially different composition.