Bryophyte diversity along an altitudinal gradient in Darién National Park, Panama

A bryophyte inventory along an altitudinal gradient on Cerro Pirre (1200 m), Darién National Park, Panama, demonstrates that the different rain forest types along the gradient (inundatedlowland, hillside-lowland, submontane, montane elfin forest) have very different species assemblages. The montane forest has the largest number of exclusive species and the largest bryophyte biomass. Species richness is greatest in the submontane forest. The bryophyte flora of Cerro Pirre is not exceedingly rich in species owing to the rather low elevation of the mountain and the seasonal climate in the adjacent coastal plain. Nevertheless, the distinct altitudinal diversification and the occurrence of a considerable number of rare hepatic taxa, demonstrate the importance of Darién National Park as an area of plant conservation. Forty hepatic species are reported as new to Panama. Darién National Park, created in 1980, is the largest nature reserve in the Republic of Panama and one of the largest in Central America. It is located in the Province of Darién along the border with Colombia and has a surface area of 579.000 hectares (Fig. 1). The park contains the largest hydrographic watershed in the country, that of the Tuira river and its tributaries. In 1981 the park was included in UNESCO’s list of World Patrimonies and two years later, in 1983, it was declared a Reserve of the Biosphere. The altitudinal gradient inventoried was located at Cerro Pirre (1200 m). This is the highest peak of the Serranía de Pirre, a mountain ridge located in the central portion of the park. The ridge extends northwards for about 35 kilometers from the Colombian border and is composed of Cretaceous igneous rocks (Myers 1969, Dalfelt and Morales 1988). The climate of the area is humidtropical,the mean annual temperature at the base of the mountain ranges between 22-25 degrees Celsius and the mean annual rainfall is over 2500 mm, with a pronounced dry season during JanuaryApril. Northern winds prevail from the end of December to April, while mild and variable southern winds predominate from May to December (Dalfelt and Morales 1978). A cooler climate with frequent clouds and mist occurs at the summit of Cerro Pirre. Virgin evergreen rain forest covers the slopes of the mountain and an elfin-type montane forest is found at the summit. The bryophyte flora of the Darién National Park is very poorly known. In recent years some bryophyte collecting in the park has been done by Panamanian and North American collectors but virtually nothing has been published on these