STEVENS, PETER F. Missouri Botanical Garden, St Louis, MO 63166, Department of Biology, University of Missouri, St Louis.. - Angiosperm phylogeny and morphology: characterisations of "all" clades of subfamilies and above.
The tree on which the Angiosperm Phylogeny group based orders, etc.,
together with elaborations since, allow morphological (inc. chemical,
anatomical) characters to be optimized (but cautiously) on the
tree. Characterizations of well-supported lineages from genera groups
upwards, and for all lineages at the family level and above, can be
provided. These characterizations are part of a web-based resource
that also includes literature, character definitions, synonymies, and
photographs. Although only an interim solution to our changing
understanding of phylogenetic relationships and to the absence of an
archived database in which individual observations are linked to
literature records (databases of character states would be
inadequate), it provides a heuristic resource for both research and
teaching that is archived and updated every six months. Characters and
states can be considered in a local context, so allowing a more
sensitive treatment of variation. Thus fruits need not be considered
as "types", but as morphologies whose elements can be teased
apart and treated independently. Interesting perspectives on the
evolution of trimerous, pentamerous and bisymmetrical flowers, and of
floral evolution in general, quickly become apparent - for instance,
the plesiomorphic monocot flower differs in basic construction from
that of both many Commelinid and core Eudicot flowers - as do
differences in variation patterns within the units that we
conventionally discuss as families. The questionable nature of the
idea of "family variation" promulgated in ordinary texts
becomes inescapable. Family characterizations become ever shorter as
data are added and character states are removed to appropriate
hierarchical levels, our knowledge of evolution thereby simultaneously
increasing, and the many gaps in our basic morphological knowledge
also become glaringly evident.
Key words: Angiosperm Phylogeny Group, angiosperms, clade characterisations, morphology, phylogeny