BACKGROUND AND AIMS: Previous work on the pantropical genus Ixora has revealed an Afro-Madagascan clade, but as yet no study has focused in detail on the evolutionary history and morphological trends in this group. Here the evolutionary history of Afro-Madagascan Ixora spp. (a clade of approx. 80 taxa) is investigated and the phylogenetic trees compared with several key morphological traits in taxa occurring in Madagascar. METHODS: Phylogenetic relationships of Afro-Madagascan Ixora are assessed using sequence data from four plastid regions (petD, rps16, rpoB-trnC and trnL-trnF) and nuclear ribosomal external transcribed spacer (ETS) and internal transcribed spacer (ITS) regions. The phylogenetic distribution of key morphological characters is assessed. Bayesian inference (implemented in BEAST) is used to estimate the temporal origin of Ixora based on fossil evidence. KEY RESULTS: Two separate lineages of Madagascan taxa are recovered, one of which is nested in a group of East African taxa. Divergence in Ixora is estimated to have commenced during the mid Miocene, with extensive cladogenesis occurring in the Afro-Madagascan clade during the Pliocene onwards. CONCLUSIONS: Both lineages of Madagascan Ixora exhibit morphological innovations that are rare throughout the rest of the genus, including a trend towards pauciflorous inflorescences and a trend towards extreme corolla tube length, suggesting that the same ecological and selective pressures are acting upon taxa from both Madagascan lineages. Novel ecological opportunities resulting from climate-induced habitat fragmentation and corolla tube length diversification are likely to have facilitated species radiation on Madagascar.
BACKGROUND AND AIMS: Previous work on the pantropical genus Ixora has revealed an Afro-Madagascan clade, but as yet no study has focused in detail on the evolutionary history and morphological trends in this group. Here the evolutionary history of Afro-Madagascan Ixora spp. (a clade of approx. 80 taxa) is investigated and the phylogenetic trees compared with several key morphological traits in taxa occurring in Madagascar. METHODS: Phylogenetic relationships of Afro-Madagascan Ixora are assessed using sequence data from four plastid regions (petD, rps16, rpoB-trnC and trnL-trnF) and nuclear ribosomal external transcribed spacer (ETS) and internal transcribed spacer (ITS) regions. The phylogenetic distribution of key morphological characters is assessed. Bayesian inference (implemented in BEAST) is used to estimate the temporal origin of Ixora based on fossil evidence. KEY RESULTS: Two separate lineages of Madagascan taxa are recovered, one of which is nested in a group of East African taxa. Divergence in Ixora is estimated to have commenced during the mid Miocene, with extensive cladogenesis occurring in the Afro-Madagascan clade during the Pliocene onwards. CONCLUSIONS: Both lineages of Madagascan Ixora exhibit morphological innovations that are rare throughout the rest of the genus, including a trend towards pauciflorous inflorescences and a trend towards extreme corolla tube length, suggesting that the same ecological and selective pressures are acting upon taxa from both Madagascan lineages. Novel ecological opportunities resulting from climate-induced habitat fragmentation and corolla tube length diversification are likely to have facilitated species radiation on Madagascar.
Authors: Olivier Maurin; Aaron P Davis; Michael Chester; Esther F Mvungi; Yasmina Jaufeerally-Fakim; Michael F Fay Journal: Ann Bot Date: 2007-10-22 Impact factor: 4.357
Authors: Steven B Janssens; Eric B Knox; Suzy Huysmans; Erik F Smets; Vincent S F T Merckx Journal: Mol Phylogenet Evol Date: 2009-05-03 Impact factor: 4.286
Authors: Thomas L P Couvreur; Pierre Sepulchre; Gilles Dauby; Anne Blach-Overgaard; Vincent Deblauwe; Steven Dessein; Vincent Droissart; Oliver J Hardy; David J Harris; Steven B Janssens; Alexandra C Ley; Barbara A Mackinder; Bonaventure Sonké; Marc S M Sosef; Tariq Stévart; Jens-Christian Svenning; Jan J Wieringa; Adama Faye; Alain D Missoup; Krystal A Tolley; Violaine Nicolas; Stéphan Ntie; Frédiéric Fluteau; Cécile Robin; Francois Guillocheau; Doris Barboni Journal: Biol Rev Camb Philos Soc Date: 2020-09-13