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Speciation in lichens of the Ramalin a siliquosa complex (Ascomycotina, Ramalinaceae): gene flow and reproductive isolation
Author(s) -
Culberson William Louis,
Culberson Chicita F.,
Johnson Anita
Publication year - 1993
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.1002/j.1537-2197.1993.tb15393.x
Subject(s) - chemotype , biology , supralittoral zone , reproductive isolation , lichen , gene flow , botany , genetic algorithm , ecology , evolutionary biology , gene , genetics , population , genetic variation , intertidal zone , demography , sociology , essential oil
The lichens of the rock‐inhabiting Ramalina siliquosa complex of maritime cliffs of western Europe are differentiated into six chemotypes characterized by a replacement series of β ‐orcinol depsidones. These chemotypes are sharply zoned from the most sheltered to the most exposed positions in the supralittoral zone. Since artificial crosses in lichens are impossible, the breeding system was investigated by an analysis of the progeny of matemals from nature—some growing in pure zones and others growing intermixed with different chemotypes where zones overlap. Overall, the chemotypes are highly reproductively isolated, the progeny tending to be chemically identical to their respective maternal individuals. Only one pair of chemotypes appears to represent a clear polymorphism; the remainder are apparently ecologically differentiated sibling species. Two chemotypes, which interbreed where their zones overlap, are apparently kept distinct by strong selection against unadapted sporelings in the “wrong” niche. Spermatia function over only short distances, also contributing to the reproductive isolation.