The foliicolous lichen flora of Mexico. V. Biogeographical affinities, altitudinal preferences, and an updated checklist of 293 species

Abstract

An inventory of foliicolous lichens in Mexican lowland and montane rainforest revealed a total of 288 species, 238 of which are new records for the country, raising the number of reported lichen species to c. 1800. Among the new records, there are 29 recently described species and four new records for the Neotropics and the Americas, while five taxa are for the first time reported for Central America. The 293 species now known from Mexico comprise nearly two-thirds pantropical to cosmopolitan or intercontinentally distributed taxa, whereas little more than one-third are Neotropical or American, and only 6% are potentially endemic to the country. A comparison with other lowland and montane rainforest sites in Guatemala, Costa Rica and Ecuador shows that on average lowland sites have twice as many species as montane sites. Also, the differentiation in species composition between lowland and montane sites within the same region is more pronounced (63-75% similarity) than that between adjacent regions (96-99% similarity for lowland sites and 83-87% similarity for montane sites). This means that altitudinal preferences affect species composition more strongly than geographical differentiation. The latter is a function of distance, however, while Mexican and Guatemalan lowland (montane) sites share 96% (83%) of the species, these values drop to 74% (72%) when comparing Mexico with Ecuador. Nevertheless, overall floristic similarity is very high, with the lowest value of 54% shared species found between Mexican lowland and Costa Rican montane forest.