High Floristic Endemism in Low Cloud Forests of Panama

Abstract

Among unusually low and isolated ridges and peaks of volcanic origin in Panama occur cloud forests having a high frequency of endemic plants. Exploration of these botanically ignored forests is urgently needed in face of their impending destruction. ENDEMISM, ESPECIALLY OF ferns and epiphytes, is characteristic of the cloud forest vegetation in the neotropics (e.g., Howard 1970 in Puerto Rico, Martin 1955 in Mexico, Standley and Steyermark 1945 in Guatemala). It is a striking feature of the high cloud forests reaching 2000 m and above in western Panama, as well as the lower mountain rain forest, yet endemism is quite varied and is known for most plant families found in this type of vegetation in Panama and adjacent Costa Rica. What is less known and appreciated is the vegetation of the lower cloud forest, a community widespread in isolated ridges and peaks throughout central and eastern Panama. The majority of these forests rarely exceed 1000 m in elevation and often are much lower in central Panama. Indeed, they are the lowest in Central and South America (Myers 1969). Moreover, low ridges facing the Atlantic in particular and reaching elevations of only about 500 m simulate cloud forests by being shrouded in mist much of the time. Both categories are considered cloud forests in this note. The peak of one of these, Cerro Jefe (Provincia de Panam'a), is covered with igneous, volcanic rock called tuff, probably rhyolitic tuff. It is composed of compacted ash and larger fragments of min