| A monograph of the genus Symphonia (Clusiaceae) is presented. Traditionally, 18 species were recognized, 16 of these in Madagascar, the remaining two in Africa and the New World tropics, respectively. This has been revised to 24 species, which include the establishment of 7 novel species, 3 synonomies, and a new subspecific arrangement of the widespread species S. gabonensis in Africa and the Americas, based on an analysis of morphological variation within the genus.; Symphonia is unified as a genus by its consistent basic floral and vegetative construction, varying in just a few floral and vegetative characters. In Madagascar, the genus shows a wide range of variation these characters, whereas in the neotropics, they are virtually invariant. To identify which factors account for variation in the genus, and whether these factors are useful in its taxonomic delimitation, separate principal components analyses (PCA's) were performed, using selected characters for species in northern Madagascar and the neotropics. Results of these analyses indicate that in the neotropics, there are two morphological clusters, corresponding to S. gabonensis and S. globulifera, each having a wide range of variation within them. The eight species examined in Madagascar formed more or less distinct, though overlapping clusters, each having a fairly narrow range of variation. In both regions, floral characters were of primary importance in explaining variation, followed by leaf characters.; Field observations of the floral phenology of Symphonia clusioides and S. microphylla suggest that flowers are protandrous, and are both outcrossing and self-compatible. There is also evidence of asexual reproduction, either vegetatively by runners, and possibly via agamospermous apomixis. Observed pollinators include hummingbirds (in the neotropics), perching birds, or insects. An experiment involving selective exclusion of pollinators from inflorescences suggests that individuals with flowers larger than 1 cm are predominantly bird-pollinated, while those with smaller flowers (e.g. less than 0.8 cm) are mainly pollinated by insects.; Separate hypotheses regarding the origin and diversification of the genus postulate either an origin in Madagascar with subsequent dispersals to Africa and the new world, an origin in Africa, or an origin in the neotropics. To test these hypotheses, a phylogenetic analysis utilizing the internal transcribed spacer (ITS) region of nuclear ribosomal DNA was conducted. The resulting phylogeny confirmed the monophyly of two clades, a Madagascan clade and an African/neotropical clade. To estimate divergence times, a molecular clock analysis was performed on this phylogeny, using fossil data from Nigeria dating from 40 Ma, and from Mexico dating from 23 Ma. Results from this analysis suggest an African origin of the genus, with a basal split occurring at approximately 55–31.7 Ma and a migration from Africa to the neotropics occurring at approximately 29–25.4 Ma. |
