FEILD, TAYLOR* and N. MICHELE HOLBROOK. Havard University, 16 Divinity Ave., BioLabs, Cambridge, MA, 02138. - Functional physiology of Amborella and 'ITA' plants.
Recent phylogenetic studies have placed the extant lineages
Amborella, Nymphaeales, and a clade including, Illiciales,
Trimenia, and Austrobaileya (the 'ITA clade') near the
base of the angiosperm tree. Amborella and ITA members share a
suite of ecophysiological and morphological traits related to their
occurrence in wet forest understory habitats. In particular,
Amborella and ITA members exhibit a variety of growth forms
ranging from shrubs to woody vines and a number of physiological
traits associated with adaptation to shade. This suggests that
angiosperms arose in shady, wet forest understory habitats. In
contrast, Nymphaeales possess a suite of ecophysiological features
generally associated with sunny to shady aquatic environments. Because
these specialized ecophysiological features are closely linked with
the aquatic habit, Nymphaeales may represent a separate ecological
experiment and thus have little bearing on the ecological
circumstances surrounding the origin of the angiosperms. A view of the
earliest flowering plants as understory shrubs and vines growing in
wet environments differs from previous suggestions that the first
angiosperms arose in disturbed, exposed, and semi-arid environments.
However, further work on the ecophysiology, phylogenetic
relationships, and fossil history of these lineages is necessary to
clarify how faithfully the modern representatives of the
Amborella and ITA lineages reflect the ecological roles and
environmental conditions surrounding the origin of the angiosperms.
Key words: Amborella , basal angiosperms