Diversity and Biogeography of Lichens in Neotropical Montane Oak Forests

6.4 Conclusions

The neotropical montane oak forests harbour a rich lichen flora, which is currently very little known. A preliminary list of 464 species encountered in such forests suggests that the species richness is at least comparable with that of temperate oak forests, but probably the actual diversity is at least twice as large. Most of the lichens have a wide distribution in the neotropics, often also in the other tropical regions, sometimes even with extensions into the temperate zones. They are apparently able to colonize various tree species under tropical conditions, and have no strong affinity with oaks in the neotropics. Only 17 species are, as far as is currently known, restricted to the neotropical oak countries — 11 to Mexico, five to the region Colombia-Costa Rica, and one from Costa Rica to Chiapas. Information about their host trees is scanty, and there is no evidence that they are bound to oak or oak forest. Noteworthy are nine species occurring mainly in the northern temperate zone, which have their southern limit in the oak forests of Chiapas or Costa Rica, four predominantly Caribbean species which reach the area, and 16 species which have their northern limit in the area. They are the only evidence for a bridge function of the area for lichens.