The genus Pleurothallis R.Br., the center of diversity of which is located in Andean montane forests, is represented by ca. 80 species in the Caribbean. Recent collections of plant material and ecological data in Cuba (1996-1999) has revealed a new picture of phytogeography and natural variability of the pleurothallid taxa. Almost all species inhabit an area much larger than previously assumed. A high degree of variability even within populations calls for a much broader species concept than has been employed so far. The majority of taxa show a close association with the geology of a given locality. There are three groups to which the Cuban species can be attributed: 1) taxa that are confined to habitats on serpentine, 2) those that can be found on magmatic ground in the Sierra Maestra, and finally 3) taxa that dominate on limestone. Representatives restricted to serpentine (30% of the is Cuban taxa) are endemic to the northern and eastern regions of Oriente. Due to the high degree of endemism (ca. 60%), there are only restricted relationships with other neotropical regions. They include connections especially with the other islands of the Greater Antilles (20%) as well as Central and northern South America (30%). Data have to be treated with caution however, due to the preliminary status of investigation. Several cases of ecological vicariancy are found, concerning flowering period (P. bissei Luer and P. papulifolia Luer) and flower color (P. wrightii Rchb. f. and P. gemina Stenzel). Pleurothallis prostrata Lindl. and P. parvula Ames & Schweinf. occur in northern and southern Oriente, respectively (edaphic vicariancy). The close relationship is expressed in habit, flower morphology as well as palynological characteristics. Pairs of apparently vicarious species in Cuba on one hand and Jamaica, Hispaniola, the Cayman Islands and Central America on the other suggest a mode of speciation that is triggered by the migration from one island to the other. These "migrating routes" interestingly coincide with the major direction (SE to NW) of Caribbean hurricanes. In the course of those climatic impacts, seeds, plants or entire populations might have been transported to other islands, where new environmental conditions might have triggered morphological evolution. The genus is characterized finally by a dynamic and intensive evolution which is backed by recent collections of habitually modified plants (compared with the type collection) and common but undescribed species even in thoroughly explored areas like Moa (P. llamachoi Luer).