10.5061/DRYAD.08KPRR4ZD
LaGreca, Scott
0000-0002-1988-0437
Duke University
A molecular phylogenetic evaluation of the Ramalina siliquosa complex,
with notes on species circumscription and relationships within Ramalina
Dryad
dataset
2020
2020-01-06T00:00:00Z
2020-01-06T00:00:00Z
en
317759 bytes
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CC0 1.0 Universal (CC0 1.0) Public Domain Dedication
Lichens of the Ramalina siliquosa complex dominate seashore cliffs in
Europe and Southeast Asia, but their taxonomy has been vigorously debated
for over a century. On many cliffs, they exhibit a bewildering zonation of
chemotypes that resembles the classic zonation of organisms that occupy
the littoral zone below. Do the chemotypes represent separate species, or
infraspecific variation? To better understand the systematics of this
group, sequences from four genetic loci (ITS, IGS RPB1 and RPB2) were
obtained for 59 samples from Denmark, France, Iceland, Norway, the UK,
Japan and Korea, including all major chemotypes. Maximum likelihood
analysis of these sequences, together with sequences from 36
other Ramalina species, reveals that the complex comprises two distinct
phylogenetic lineages, each including multiple chemotypes. These two
putative species-level lineages correspond to the currently accepted
taxa R. cuspidata and R. siliquosa. There is no evidence that these two
species are phylogenetic sister species. Because of this, the explanation
of this chemotype complex as an example of “sibling speciation” is
rejected. Specimens traditionally called “R. siliquosa” from Southeast
Asia form a third clade, identified here as R. semicuspidata, with an
additional, divaricatic acid chemotype. Other results include a robustly
supported clade of Ramalina species that produce medullary depsides and
depsidones; this clade includes another well-supported clade of
southeastern United States coastal plain and tropical Ramalina species. By
contrast, large, strap-shaped Ramalina species that lack medullary
depsides and depsidones occur in separate lineages. In addition, close
relationships between the following groups of species are indicated: R.
farinacea with R. subfarinacea; R. fraxinea with R. leptocarpha, R.
menziesii and R. subleptocarpha; and R. sinensis with R. unifolia.
Further, a new, variolaric-only chemotype is reported for R. farinacea;
and a new, acid-deficient chemotype is reported for a more broadly
circumscribed R. culbersoniorum.