Malagasy
Dracaena (Ruscaceae) are divided into four species and 14 varieties, all of them showing a high level of morphological diversity and
a putatively artefactual circumscription. In order to reveal relationships between those entangled entities, a span of Malagasy
Dracaena were sampled and analyzed using cpDNA sequences and AFLP. The cpDNA analyses resolved three biogeographic clades that are
mostly inconsistent with morphology, since similar phenotypes are found across the three clades. Bayesian inference clustering
analyses based on the AFLP were not in accordance with the cpDNA analysis. This result might be explained by (1) a recent
origin of the Malagasy species of
Dracaena with an incomplete sorting of chloroplast lineages; (2) a high amount of hybridizations; (3) a complex migration pattern.
Interestingly, when the AFLP are analyzed using the parsimony criterion, a trend towards a directional evolution of inflorescence
types and ecological features was observed. This might be considered either as phenotypic plasticity and/or as the result
of fast evolution in flower characters according to habitat preferences. Overall, our results point to the difficulty of defining
evolutionarily significant units in Malagasy
Dracaena, emphasizing the complex speciation processes taking place in tropical regions.
Keywords AFLP - Biogeography - cpDNA - Incomplete lineage sorting - Malagasy Dracaena
- Phenotypic plasticity