Abstract Detail

The flora of Madagascar: uncovering mechanisms for diversification

Linan, Alexander [1], Schatz, George [2], Lowry, Porter [2], Miller, Allison [3], Edwards, Christine [4].

Evolutionary relationships of ebonies (Diospyros L.) across Western Indian Ocean islands.

In the Western Indian Ocean, Madagascar and the Mascarene Islands are home to nearly a third of the estimated 860 species in the genus Diospyros. However, the evolutionary relationships among taxa inhabiting these islands and the wider region remain largely unknown. The objectives of this study were to use phylogenetic methods to understand 1) broad-scale biogeographic patterns of Diospyros in the Western Indian Ocean in relation to other geographic regions, and 2) the composition, evolutionary relationships, and morphological features of clades of Diospyros in the region, with a particular focus on the relationship between Malagasy Diospyros and taxa in section Forbesia, a group thought to contain taxa from the Mascarenes and Africa. To address these objectives, we conducted Bayesian and maximum likelihood phylogenetic analyses as well as divergence time estimation using a sample of 147 Diospyros taxa, 51 of which occur in either Madagascar or the Mascarenes, based on four chloroplast regions (rbcL, atpB, trnS-G, matK-trnK intron). Phylogeny reconstruction grouped most Diospyros from Madagascar into a large clade, with taxa from other islands/areas as far away as New Caledonia nested within subclades that were predominantly Malagasy. All these clades diverged long after the breakup of Gondwana, suggesting that long-distance dispersal rather than vicariance was responsible for the observed patterns of diversity. Although one instance of colonization from Africa to Madagascar was revealed, our results show that multiple dispersal events from Madagascar likely gave rise to lineages in the Mascarenes, New Caledonia, and other areas, indicating that this biodiversity hotspot may have acted as an important source area for the genus. Diospyros from Madagascar were grouped into eight clades, one of which contained a single Mascarene species D. tesselaria. All other Mascarene species belong to a clade that also includes species from Africa, which together have been assigned to section Forbesia, along with Malagasy species not previously identified as being part of the section; these results therefore, suggest that the section should be expanded. Our initial phylogenetic results for Indian Ocean Diospyros revealed several novel relationships among taxa from the region that are consistent with distinctive morphological features.

1 - Saint Louis Univeristy, Biology, Biology Extension Building, 1008 S. Spring Ave., St. Louis, MO, 63103, USA
2 - Missouri Botanical Garden, Africa and Madagascar Department, P.O. Box 299, St. Louis, MO, 63166-0299, USA
3 - Saint Louis University, Biology, St. Louis, Biology Extension Building, Saint Louis, MO, 63108, United States
4 - Missouri Botanical Garden, Center for Conservation and Sustainable Development (CCSD), P.O. box 299, St. Louis, MO, 63166-0299, USA

Keywords:
Mascarenes
Diospyros
Ebenaceae
Madagascar
Molecular phylogeny.

Presentation Type: Colloquium Presentations
Session: C08, The flora of Madagascar: uncovering mechanisms for diversification
Location: 101/Mayo Civic Center
Date: Tuesday, July 24th, 2018
Time: 1:45 PM
Number: C08002
Abstract ID:711
Candidate for Awards:None