Rapid radiation of angraecoids (Orchidaceae, Angraecinae) in tropical Africa characterised by multiple karyotypic shifts under major environmental instability

[Display omitted] •Updated phylogenetic and nomenclatural framework for angraecoids based on 245 taxa.•Annotated checklist of chromosome number counts for 126 angraecoid orchids.•Dated tree suggests a common dispersal history for angraecoids and Bulbophyllum.•Karyotypic shifts parallel cladogenesis/...

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Published in:Molecular phylogenetics and evolution 2021-06, Vol.159, p.107105-107105, Article 107105
Main Authors: Farminhão, João N.M., Verlynde, Simon, Kaymak, Esra, Droissart, Vincent, Simo-Droissart, Murielle, Collobert, Géromine, Martos, Florent, Stévart, Tariq
Format: Article
Language:English
Subjects:
African rainforest
Angraecum
Biodiversity
Biodiversity and Ecology
Botanics
Diversification analysis
Ecology, environment
Ecosystems
Environmental Sciences
Epiphyte
Life Sciences
Phylogenetic nomenclature
Pseudotriploid
Systematics, Phylogenetics and taxonomy
Vegetal Biology
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Summary:[Display omitted] •Updated phylogenetic and nomenclatural framework for angraecoids based on 245 taxa.•Annotated checklist of chromosome number counts for 126 angraecoid orchids.•Dated tree suggests a common dispersal history for angraecoids and Bulbophyllum.•Karyotypic shifts parallel cladogenesis/higher morphodiversity in mainland Africa.•Diversification uncoupled with karyoevolution and faster speciation in Madagascar. Angraecoid orchids present a remarkable diversity of chromosome numbers, which makes them a highly suitable system for exploring the impact of karyotypic changes on cladogenesis, diversification and morphological differentiation. We compiled an annotated cytotaxonomic checklist for 126 species of Angraecinae, which was utilised to reconstruct chromosomal evolution using a newly-produced, near-comprehensive phylogenetic tree that includes 245 angraecoid taxa. In tandem with this improved phylogenetic framework, using combined Bayesian, maximum likelihood and parsimony approaches on ITS-1 and five plastid markers, we propose a new cladistic nomenclature for the angraecoids, and we estimate a new timeframe for angraecoid radiation based on a secondary calibration, and calculate diversification rates using a Bayesian approach. Coincident divergence dates between clades with identical geographical distributions in the angraecoids and the pantropical orchid genus Bulbophyllum suggest that the same events may have intervened in the dispersal of these two epiphytic groups between Asia, continental Africa, Madagascar and the Neotropics. The major angraecoid lineages probably began to differentiate in the Middle Miocene, and most genera and species emerged respectively around the Late Miocene-Pliocene boundary and the Pleistocene. Ancestral state reconstruction using maximum likelihood estimation revealed an eventful karyotypic history dominated by descending dysploidy. Karyotypic shifts seem to have paralleled cladogenesis in continental tropical Africa, where approximately 90% of the species have descended from at least one inferred transition from n = 17–18 to n = 25 during the Middle Miocene Climatic Transition, followed by some clade-specific descending and ascending dysploidy from the Late Miocene to the Pleistocene. Conversely, detected polyploidy is restricted to a few species lineages mostly originating during the Pleistocene. No increases in net diversification could be related to chromosome number changes, and the apparent net diversific
ISSN:1055-7903
1095-9513
DOI:10.1016/j.ympev.2021.107105