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Biol Lett. Oct 23, 2010; 6(5): 703–707.
Published online Mar 24, 2010. doi:  10.1098/rsbl.2010.0095
PMCID: PMC2936138
Bayesian island biogeography in a continental setting: the Rand Flora case
Isabel Sanmartín,1* Cajsa Lisa Anderson,1 Marisa Alarcon,1 Fredrik Ronquist,2 and Juan José Aldasoro1
1Real Jardin Botanico, CSIC, Plaza de Murillo 2, 28014 Madrid, Spain
2Department of Entomology, Swedish Museum of Natural History, PO Box 50007, 104 05 Stockholm, Sweden
*Author for correspondence (isanmartin/at/
These authors contributed equally to the study.
Received January 28, 2010; Accepted March 3, 2010.
We here explore the use of a Bayesian approach to island biogeography for disentangling the evolutionary origins of a continental-scale floristic pattern, the enigmatic ‘Rand Flora’. The existence of disjunct distributions across many plant lineages between Macaronesia–northwest Africa, Horn of Africa–southern Arabia and east–south Africa has long intrigued botanists, but only now can we start analysing it within a statistical framework.
Phylogenetic and distributional data from 13 plant lineages exhibiting this disjunct distribution were analysed to estimate area carrying capacities and historical rates of biotic exchange between areas. The results indicate that there has been little exchange between southern Africa and the northern African region, and that this exchange occurred via east Africa. Northwest Africa–Macaronesia shows the smallest carrying capacity but highest dispersal rate with other regions, suggesting that its flora was built up by immigration of lineages, probably from the Mediterranean region and western Asia. In contrast, southern Africa shows the highest carrying capacity and lowest dispersal rate, suggesting a flora formed by in situ diversification.
We discuss further improvements of the method for addressing more complex hypotheses, such as asymmetric dispersal between regions or repeated cyclical events.
Keywords: Rand Flora, disjunct pattern, Bayesian analysis, Africa, island biogeography
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