Diversification of myco-heterotrophic angiosperms: Evidence from Burmanniaceae
1 Laboratory of Plant Systematics, K.U. Leuven, Kasteelpark Arenberg 31, P.O. Box 2437, BE-3001 Leuven, Belgium
2 National Herbarium of the Netherlands, Wageningen University Branch, Generaal Foulkesweg 37, NL-6703 BL Wageningen, The Netherlands
3 Centre for Tropical Forest Sciences (CTFS), University of Buea, Department of Plant & Animal Sciences, P.O. Box 63, Buea, Cameroon
4 National Herbarium of the Netherlands, Leiden University Branch, P.O. Box 9514, NL-2300 RA, Leiden, The Netherlands
BMC Evolutionary Biology 2008, 8:178 doi:10.1186/1471-2148-8-178Published: 23 June 2008
Myco-heterotrophy evolved independently several times during angiosperm evolution. Although many species of myco-heterotrophic plants are highly endemic and long-distance dispersal seems unlikely, some genera are widely dispersed and have pantropical distributions, often with large disjunctions. Traditionally this has been interpreted as evidence for an old age of these taxa. However, due to their scarcity and highly reduced plastid genomes our understanding about the evolutionary histories of the angiosperm myco-heterotrophic groups is poor.
We provide a hypothesis for the diversification of the myco-heterotrophic family Burmanniaceae. Phylogenetic inference, combined with biogeographical analyses, molecular divergence time estimates, and diversification analyses suggest that Burmanniaceae originated in West Gondwana and started to diversify during the Late Cretaceous. Diversification and migration of the species-rich pantropical genera Burmannia and Gymnosiphon display congruent patterns. Diversification began during the Eocene, when global temperatures peaked and tropical forests occurred at low latitudes. Simultaneous migration from the New to the Old World in Burmannia and Gymnosiphon occurred via boreotropical migration routes. Subsequent Oligocene cooling and breakup of boreotropical flora ended New-Old World migration and caused a gradual decrease in diversification rate in Burmanniaceae.
Our results indicate that extant diversity and pantropical distribution of myco-heterotrophic Burmanniaceae is the result of diversification and boreotropical migration during the Eocene when tropical rain forest expanded dramatically.