HEARN, DAVID JOHN. University of Arizona, Department of Ecology and Evolutionary Biology, BSW Room 310, Tucson, AZ 85721-0088. - Growth form evolution in Adenia and correlations with phytochemistry.
The genus Adenia (Passifloraceae) provides a model system with
which to investigate the relationship between growth form and
phytochemistry. With ca. 90 species the genus has a diverse and varied
pharmacopoeia and at least seven distinct growth forms. An association
between growth form and chemistry is expected based on theoretical
predictions. I mapped cyanogenesis on the phylogeny of Adenia
to reveal that 4 of the 5 putative shifts from ancestral tendrillate
vines to growth forms without tendrils are in association with low
cyanogenesis as expected. The phylogeny based on ITS sequence data and
an extensive sampling of African and Madagascan species of
Adenia supports 5 main lineages. Extrafloral nectary
superstructure in large part supports the molecular characterization.
Individuals in the most basal lineage of Adenia all possess
spatulate glands at the leaf blade base. The next most ancient lineage
has members that are tuberous vines and herbs. Members of this lineage
share paired and upturned glands at the petiole-blade junction. A more
recent lineage contains a wet-tropical African lineage and a
dry-habitat African and Madagascan lineage. The wet-tropical lineage
has lianas and vines with paired auriculate glands at the
blade-petiole junction. The dry-habitat African and Malagasy lineage
possesses species with succulence and often slightly recessed glands
at the base of the leaf (although some Madagascan species are
autopomorphic). The lineage that is sister to this more recent branch
is least characterized by gland structure, but possesses a diversity
of gland structures and growth forms. Research is underway to relate
anatomical features with phytochemistry to rigorously test whether
changes in anatomy (hence changes in growth form) are correlated with
changes in phytochemistry.
Key words: Adenia, Africa, cyanogenesis, growth form, Passifloraceae, phylogenetics