Pteridophytes of a Semiarid Natural Protected Area in Central Mexico

In Mexico, little is known about species richness and distribution patterns of ferns and lycopods (Pteridophytes) in dry climates, since both groups have been studied mainly in wet environments. The Barranca de Metztitlán Biosphere Reserve, in the state of Hidalgo in central Mexico, is covered mostly with xerophytic vegetation and has a rugged landscape with contrasting climate areas. It was selected for this study as an appropriate model for analyzing changes in the composition, richness, and distribution of fern and lycopod species by elevation. To establish the relationship between species composition and richness along the elevation gradient, simple and multivariate correlation techniques were used (TWISPAN and detrended correspondence analysis). From a total of 464 specimens collected, 69 fern species and two hybrids, and eight lycopod species were identified. Three of the species had not previously been recorded for the state of Hidalgo: Pellaea atropurpurea, Thelypteris hispidula, and Selaginella illecebrosa. Species richness of both ferns and lycopods was positively correlated with elevation due to greater water availability and lower temperature. The species replacement rate between sites was high, indicating that ferns and lycopods grow in different associations along the elevation gradient. These associations can be regarded as indicators of environmental variation (primarily temperature and moisture) and/or vegetation types in the biosphere reserve.