Aim The plant genus Bursera, with 104 species of trees and shrubs, has been used as a model for biogeographical analyses because of its high species richness and large number of endemic species. The biogeographical patterns of Bursera and their implications for its phylogenetic classification are reviewed in order that some hypotheses on the historical biogeography of tropical Mexico can be proposed.
Aim
Our aim was to analyse the temporal dynamics of areas of endemism of Bursera species (Burseraceae), a dominant element of the Mexican tropical dry forest, between the Last Glacial Maximum (LGM) and the present day. We aimed to identify stable core sectors that have held permanent populations of endemic species.
Location
Mexican dry forest.
Methods
We modelled the geographical distributions of 81 species of Bursera and identified their areas of endemism at the LGM and at present. For each area of endemism, changes in time, species composition and distribution were analysed, and a spatially explicit temporal hypothesis was formulated.
Results
Three areas of endemism supported by geographically congruent elements were identified: the Central Mexican Pacific Coast, Western Balsas, and Eastern Balsas–Tehuacán/Cuicatlán–Tehuantepec. Within them we identified stable core sectors (refugia).
Main conclusions
The areas of endemism identified represent distinct evolutionary biotic components of the Mexican dry forest. Their stable core sectors may facilitate phylogeographical predictions at the level of species or species assemblages. The framework adopted allows us to formulate spatially explicit temporal hypotheses about biotic processes, based exclusively on geographical data.
Summary
Mexican cloud forests, situated between 600 and 3000 m of elevation, exhibit a remarkable high biotic diversity. They follow a fragmented pattern, similar to that of an archipelago, that makes them suitable to vicariance modelling. A Parsimony Analysis of Endemicity (PAE) was applied to the presence/absence of 1267 species of vascular plants (gymnosperms, angiosperms, and pteridophytes) from twenty‐four patches of Mexican cloud forests, in order to postulate a preliminary hypothesis of relationships. The single cladogram obtained grouped the twenty‐four cloud forests into five clades. These results indicate that the Sierra Madre Oriental, Sierra Madre del Sur, and Serranías Meridionales floristic provinces do not represent natural units. A preliminary vicariance model is presented to explain the sequence of fragmentation of the Mexican cloud forests.
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