Title:
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Conservation and molecular systematics of the genus Cedrus.
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Cedrus is a long-lived forest tree whose extant distribution is limited to a disjunct
occurrence at the southern margin of the wide expansion range of its family Pinaceae. Its
taxonomy is marked with conflicting inferences. The position of Cedrus within Pinaceae is
unresolved between the major subfamily groupings. The infrageneric classification of
Cedrus taxa, which is based on indistinct phenotypic characters, remains highly
controversial. Within its narrow geographical boundaries, Cedrus has long been, and is
still, threatened with a diversity of degrading pressures that raise questions on the viability
of the dispersed remnant populations. The unsettled taxonomic dispute, compounded with
gaps and uncertainties in the information available on the genus, impede potential efforts
toward the conservation and sustainable management of this ancient heritage.
This study employed molecular systematics to establish a better understanding of the
phylogenetic relationships of Cedrus at the different organizational levels from genus to
species and populations. The phylogeny of Pinaceae, reconstructed from chloroplast DNA
sequences, establishes Cedrus as a monophylum and resolves its position as sister to the
rest of the Pinaceae genera. A DNA-based phylogeny of the interrelationships within
Cedrus delimits five evolutionary units which are recognized as species, emphasizing the
significance of their geographical disjunction. The evolutionary sequence of these units
defines an east-west migration trend from the Himalayas toward the Mediterranean. At the
population level, fingerprinting of the genetic diversity in the remnant Cedrus isolates of
Lebanon infers a substantial level of diversity distributed within populations with no
indication of interpopulation divergence. These findings are instrumental at defining the
future conservation of Cedrus as a genetic resource
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