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Abstract Detail


Gagnon, Edeline [1], Ringelberg, Jens [2], Bruneau, Anne [3], Lewis, Gwilym [4], Hughes, Colin [5].

The Caesalpinia group as a model for understanding biogeographical patterns of evolution.

To investigate the origins and global diversification patterns in arid habitats, we used the Caesalpinia Group (Leguminosae) as a case study. This group of c. 225 species principally occurs in the Succulent Biome, but a subset also occurs in the Savannah Biome, as well as in warm Temperate areas (deserts and prairies), and are found as shrubs, trees, lianas or herbaceous plants. In addition to reconstructing the biogeographic history of this group, we investigate whether diversification rates vary as a function of long-distance dispersal, evolution towards new biomes or changes in plant habits. A molecular dataset with all 27 genera and 84% of species of the group was used to reconstruct a time-calibrated phylogeny, using two fossil calibrations. Ancestral areas occupied by this group were reconstructed, as well as the ancestral states for plant habit and biomes. Diversification rates were estimated and tested for shifts in macro-evolutionary processes, and we also examined issues related to biome/habit co-evolution, and carried out various tests of niche conservatism (including simmap permutation and testing for phylogenetic signal). Our results suggest that the Caesalpinia Group most likely appeared in the Paleocene period, and was most likely a tree/shrub species in the Succulent Biome, either from South America or Africa. Subsequent intercontinental dispersals events were estimated to occur most frequently in the Succulent Biome. Diversification analyses demonstrated a lack of any significant rate shifts, with speciation rates slightly decelerating through time. The age and the persistence of the Caesalpinia Group, in combination with the single evolutionary rates regime, suggests long-term stability and ecological resilience of the Succulent Biome. The frequent intercontinental dispersals within this biome points to niche conservatism acting to shape diversification of this clade on a global scale.

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1 - Université de Moncton, Biologie, 18. Avenue Antonine Maillet, Pav. LT (RR C115-3), Moncton, NB, E1A 3E9, Canada
2 - Institute of Plant Systematics and Evolution , Switzerland
3 - Insti De Recherche Bio Vegetal, 4101 Rue Sherbrooke Est, Montreal, H1X 2B2, Canada
4 - Herbarium Royal Botanic Garden, Kew, Richmond, SRY, TW9 3AE, UK
5 - University Of Zurich, Institute Of Systematic Botany, Zollikerstrasse 107, Zürich, 8008 Zürich, Switzerland

climatic niche shift
Ancestral character estimation
phylogenetic biome conservatism
phylogenetic signal
phylogenetic correlation
phylogenetic correlated traits.

Presentation Type: Oral Paper
Session: 4, Biogeography
Location: 105/Mayo Civic Center
Date: Monday, July 23rd, 2018
Time: 9:30 AM
Number: 4007
Abstract ID:493
Candidate for Awards:None


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