MORT, MARK E.*, DOUGLAS E. SOLTIS, PAMELA S. SOLTIS, JAVIER FRANCISCO-ORTEGA, AND ARNOLDO SANTOS-GUERRA. Department of Biological Sciences, Eastern Illinois University, Charleston, IL 61920; School of Biological Sciences, Washington State University, Pullman, WA 99164; Department of Biology, Florida International University, Miami, FL 33199; Jardin de Aclimatacion de la Orotava, Puerto de la Cruz, Tenerife, Canary Islands, Spain. - Phylogenetics and evolution of Aeonium (Crassulaceae) and related genera on the Canary Islands.
The Macaronesian clade (Crassulaceae) includes four genera,
Aeonium, Aichryson, Greenovia, and
Monanthes, that are largely endemic to the Canary Islands. The
monophyly of this clade has been supported based on phylogenetic
analyses of Crassulaceae; however relationships within this clade
remain uncertain. To resolve relationships within this clade,
parsimony analyses were conducted on DNA sequences from several
chloroplast regions (trnL-trnF, psbA-trnH, and
matK), the internal transcribed spacers, and morphology
(Aeonium only). Phylogenetic analyses of these data sets
recover three major clades. Congruence tests were conducted on each
of these data sets as well as the topologies resulting from our
initial parsimony analyses. Several incongruent taxa were pruned from
the cpDNA data set; a combined data set was constructed; and parsimony
analyses were repeated. These analyses again recovered three clades.
The monophyly of Aichryson and Greenovia was supported;
however, Aeonium is monophyletic only if Greenovia is
included in this genus. Aeonium, the largest genus of Canary
Island Crassulaceae, comprises species that are highly diverse in
growth form, including rosette trees, candelabrum shrubs,
highly-branched shrubs, and woody rosettes. In addition, species of
Aeonium are also diverse in habit (perennial and perennial
monocarpic species) and physiology, with CAM, C3, and
CAM-C3 intermediate photosynthesis present in the genus.
Analyses of stable isotopes of carbon were conducted from field
collected leaf material to determine the degree of physiological
variation present in Aeonium. The evolution of growth forms,
habit, and physiology was investigated using our phylogenetic
hypothesis for this genus. These analyses suggest that two subclades
of Aeonium comprise taxa with similar growth forms, whereas two
subclades contain taxa that display a wide range of growth form
diversity. Monocarpy has arisen a minimum of four times in the genus.
The ancestral physiological condition for Aeonium is
C3 photosynthesis, with at least three origins of CAM
photosynthesis.
Key words: CAM, Canary Islands, Crassulaceae, diversification, phylogenetics