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Wood Anatomy of Dubautia (Asteraceae: Madiinae) in Relation to Adaptive Radiation

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Title:Wood Anatomy of Dubautia (Asteraceae: Madiinae) in Relation to Adaptive Radiation
Authors:Carlquist, Sherwin
Date Issued:Oct 1998
Publisher:University of Hawaii Press
Citation:Carlquist S. 1998. Wood anatomy of Dubautia (Asteraceae: Madiinae) in relation to adaptive radiation. Pac Sci 52(4): 356-368.
Abstract:Qualitative and quantitative features are reported for stem wood
of 13 collections of 12 species of the Hawaiian genus Dubautia. Although the
species share a basic wood plan, quantitative expressions range widely, especially
with respect to vessel element dimensions, vessel density, vessel grouping,
length of libriform fibers, and dimensions of multiseriate rays. Ecology and
habit explain most of the diversity. Variations in the ratio between vessel element
length and libriform fiber length are correlated with habit both within
Dubautia and when Dubautia is compared with Argyroxiphium and Wilkesia.
Other variation in wood is related mostly to ecology. The Dubautia species of
wet forest have high mesomorphy ratio values. Low mesomorphy ratio values
occur in species of recent or dry lava (e.g., D. scabra) or dry alpine areas (D.
menziesii); mesomorphy ratio values in the xeric species are comparable with
those in Argyroxiphium. Highly xeromorphic wood in the bog species D. waialealae
may reflect recent immigration from a dry habitat or peculiar features of
the bog habitat. The lianoid D. latifolia has notably xeromorphic wood, which
may reflect recent entry into wet forest or else the tendency for lianas in general
to have xeromorphic features that confer conductive safety. All species of
Dubautia show fiber dimorphism. Dubautia is a superb example of adaptive
radiation, in contrast to the Hawaiian Schiedea (Caryophyllaceae), which
has shifted into various habitats with little change in wood anatomy, or the
Galapagos genus Scalesia, all species of which must survive periods of drought
and have xeromorphic wood.
Appears in Collections: Pacific Science Volume 52, Number 4, 1998

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