The species was originally described as
Lichen siliquosus by the botanist
William Hudson in 1762. It was transferred to the genus
Ramalina by
Annie Lorrain Smith in 1918.
Ramalina siliquosa is part of a
complex of closely related lichen species that grow on maritime cliffs in Europe and East Asia.
Molecular phylogenetics analysis has revealed that this complex comprises three distinct evolutionary
lineages: •
Ramalina siliquosa sensu stricto – Found in Europe, includes the
hypoprotocetraric,
protocetraric and
salazinic acid chemotypes. •
Ramalina cuspidata – Also found in Europe, includes the
norstictic and
stictic acid chemotypes. •
Ramalina semicuspidata – Found in Japan and Korea, includes four chemotypes (
salazinic,
divaricatic,
protocetraric, and acid-deficient). The European species
R. siliquosa and
R. cuspidata show distinct zonation patterns on cliffs, with different chemotypes occupying different vertical zones. This zonation is not observed in the East Asian
R. semicuspidata. Contrary to previous hypotheses,
R. siliquosa and
R. cuspidata are not closely related "sibling species", but represent separate evolutionary lineages. The chemical variation and zonation patterns in this complex appear to be a result of parallel or
convergent evolution rather than recent
speciation. ==See also==