Abstract:
PREMISE: The woody plant group Memecylon (Melastomataceae) is a large clade
occupying diverse forest habitats in the Old World tropics and exhibiting high regional
endemism. Its phylogenetic relationships have been previously studied using ribosomal
DNA with extensive sampling from Africa and Madagascar. However, divergence times,
biogeography, and character evolution of Memecylon remain uninvestigated. We present
a phylogenomic analysis of Memecylon to provide a broad evolutionary perspective of this
clade.
METHODS: One hundred supercontigs of 67 Memecylon taxa were harvested from target
enrichment. The data were subjected to coalescent and concatenated phylogenetic
analyses. A timeline was provided for Memecylon evolution using fossils and secondary
calibration. The calibrated Memecylon phylogeny was used to elucidate its biogeography
and ancestral character states.
RESULTS: Relationships recovered by the phylogenomic analyses are strongly supported
in both maximum likelihood and coalescent-based
species trees. Memecylon is inferred
to have originated in Africa in the Eocene and subsequently dispersed predominantly
eastward via long-distance
dispersal (LDD), although a reverse dispersal from South Asia
westward to the Seychelles was postulated. Morphological data exhibited high levels of
homoplasy, but also showed that several vegetative and reproductive characters were
phylogenetically informative.
CONCLUSIONS: The current distribution of Memecylon appears to be the result of multiple
ancestral LDD events. Our results demonstrate the importance of the combined effect of
geographic and paleoclimatic factors in shaping the distribution of this group in the Old
World tropics. Memecylon includes a number of evolutionarily derived morphological
features that contribute to diversity within the clade.
