The distribution of woody legumes in neotropical dry forests: the Pleistocene Arc Theory 20 years on

MOGNI, V.Y.; OAKLEY, L.J.; PRADO, D.E.

EDINBURGH JOURNAL OF BOTANY

Cambridge University Press

Lugar: Edimburgo, Escocia; Año: 2015 vol. 72 p. 35 - 60

0960-4286

The Pleistocene Arc Theory (PAT) suggests that present day disjunct fragments of dry forests in central tropical South America give evidence of a previously more continuous expansion during the Pleistocene that has been disrupted by dry-cold versus humid-warm climatic cycles. This Arc extends from NE Brazil to NE Argentina and eastern Paraguay, through the Chiquitanía to NW Argentina and SW Bolivia and into the dry inter-Andean valleys in Peru and Ecuador, with intrusions into the Great Chaco. The Seasonally Dry Tropical Forests (SDTF) are floristically and physiognomically dominated by woody legumes, mostly deciduous in the dry season. In the last two decades field collection and research on legume taxa has greatly increased, with a significant number of taxonomic revisions and molecular phylogenetic studies, together with some palaeoclimatic modelling studies, having been published. The evidence accumulated in the last 23years has confirmed the Chaco and Caatingas phytogeographical provinces, with an impressive and increasing level of botanical endemism discovered. The PAT pattern has also been confirmed in support of the original hypothesis, specifically through the mapping of five selected woody Leguminosae species (Anadenanthera colubrina, Enterolobium contortisiliquum, Pterogyne nitens, Amburana cearensis and Piptadenia viridiflora). The pre-existing nuclei of South American SDTF (Caatingas, Misiones, and Piedmont) are now increased to four with the postulation of the Chiquitanía Nucleus in south-western Bolivia and bordering Paraguay. Some new endemisms are compiled from recent literature and mapped for the Misiones and Chiquitanía nuclei. The need for more botanical collections and further taxonomic, phylogenetic and demographic studies for the South American legumes are emphasized.