title: Dispersing towards Madagascar: Biogeography and evolution of the Madagascan endemics of the Spermacoceae tribe (Rubiaceae).
abstract: Despite the close proximity of the African mainland, dispersal of plant lineages towards Madagascar remains intriguing. The composition of the Madagascan flora is rather mixed and shows besides African representatives, also floral elements of India, Southeast Asia, Australia, and the Neotropics. Due to its proportionally large number of Madagascan endemics, the taxonomically troublesome Spermacoceae tribe is an interesting group to investigate the origin and evolution of the herbaceous Rubiaceae endemic to Madagascar. The phylogenetic position of these endemics were inferred using four plastid gene markers. Age estimates were obtained by expanding the Spermacoceae dataset with representatives of all Rubiaceae tribes. This allowed incorporation of multiple fossil-based calibration points from the Rubiaceae fossil record. Despite the high morphological diversity of the endemic herbaceous Spermacoceae on Madagascar, only two colonization events gave rise to their current diversity. The first clade contains Lathraeocarpa, Phylohydrax and Gomphocalyx, whereas the second Madagascan clade includes the endemic genera Astiella, Phialiphora, Thamnoldenlandia and Amphistemon. The tribe Spermacoceae is estimated to have a Late Eocene origin, and diversified during Oligocene and Miocene. The two Madagascan clades of the tribe originated in the Oligocene and radiated in the Miocene. The origin of the Madagascan Spermacoceae cannot be explained by Gondwanan vicariance but only by means of Cenozoic long distance dispersal events. Interestingly, not only colonization from Africa occurred but also long distance dispersal from the Neotropics shaped the current diversity of the Spermacoceae tribe on Madagascar.
authors.affiliation: Botanic Garden Meise, Nieuwelaan 38, BE-1860 Meise, Belgium. Electronic address: steven.janssens@botanicgardenmeise.be.
authors.forename: Steven B
authors.initials: SB
authors.lastname: Janssens
authors.affiliation: Plant Conservation and Population Biology, Kasteelpark Arenberg 31, BE-3001 Leuven, Belgium.
authors.forename: Inge
authors.initials: I
authors.lastname: Groeninckx
authors.affiliation: Botanic Garden Meise, Nieuwelaan 38, BE-1860 Meise, Belgium.
authors.forename: Petra J
authors.initials: PJ
authors.lastname: De Block
authors.affiliation: Botanic Garden Meise, Nieuwelaan 38, BE-1860 Meise, Belgium; Plant Conservation and Population Biology, Kasteelpark Arenberg 31, BE-3001 Leuven, Belgium.
authors.forename: Brecht
authors.initials: B
authors.lastname: Verstraete
authors.affiliation: Plant Conservation and Population Biology, Kasteelpark Arenberg 31, BE-3001 Leuven, Belgium; Naturalis Biodiversity Center, Leiden University, Leiden, The Netherlands.
authors.forename: Erik F
authors.initials: EF
authors.lastname: Smets
authors.affiliation: Botanic Garden Meise, Nieuwelaan 38, BE-1860 Meise, Belgium.
authors.forename: Steven
authors.initials: S
authors.lastname: Dessein
mesh_terms: D000349:Africa; D000353:Africa, Southern; D019659:Asteraceae / Q000235:genetics; D001315:Australia; D019143:Evolution, Molecular; D005580:Fossils; D049810:Genetic Speciation; D006801:Humans; D007194:India; D008270:Madagascar; D010802:Phylogeny; D058974:Phylogeography; D063148:Plant Dispersal / Q000235:genetics; D019666:Rubiaceae / Q000145:classification / Q000235:genetics*
keywords: Ancestral area reconstruction; Biogeography; Madagascar; Molecular dating; Rubiaceae; Spermacoceae