MEYER, KARSTEN* AND SUSANNE S. RENNER. Institut fuer Spezielle Botanik, University of Mainz, D-55099 Mainz; Department of Biology, University of Missouri-St. Louis, St. Louis, MO 63121. - Long distance dispersal in Melastomeae: from South America to Africa to Madagascar and SE Asia.
Melastomeae are pantropically distributed and comprise ~550 spp. in
the New World, including the 13 spp. of Rhexia in North America, 170
spp. in Africa, 70 in Madagascar, and 50 spp. of Melastoma and
Osbeckia in SE Asia and tropical Australia. The monophyly of
Melastomeae is strongly supported by combined rbcL, ndhF, and rpl16
cpDNA sequences analyzed under maximum likelihood, distance, and
parsimony criteria. Melastomeae are closest to Microlicieae, a clade
currently appearing endemic in the neotropics. Melastomeae-type seeds
have been reported from the Early Miocene of Eurasia (~20 MYBP), while
the oldest records for the family are Paleocene (~60 MYBP) pollen
grains from Colombia and leaves from North America. A molecular
phylogeny of Melastomataceae (Clausing and Renner, submitted) shows
Melastomeae branching off relatively late and paleotropical
Melastomeae forming a clade within neotropical Melastomeae. This
suggests a relatively recent neotropical origin of Melastomeae,
followed by dispersal to North America, Africa and Europe, Madagascar,
SE Asia, and Australia. Molecular clock estimates, using rbcL and
ndhF genetic distances calibrated with the fossils, imply a
mid-Tertiary age for the separation between Central American and North
American genera, and arrival and dispersal of Melastoma and Osbeckia
in SE Asia from Africa/Madagascar during the Pliocene.
Key words: long distance dispersal, Melastoma, molecular clock, Osbeckia, Rhexia