Epilithic algae and cyanoprokaryotes from the Archaeological Site of Yaxchilan, Chiapas, Mexico

The epilithic algae and cyanoprokaryotes that inhabit the Archaeological Zone of Yaxchilan, Chiapas, cover most of the walls of buildings; it is a site located in the Lacandon Jungle, next to the Usumacinta river with a very high relative humidity. The aim of this work was to document the species of algae and cyanoprokaryotes that grow on the archaeological monuments of this area, based on the microscopic morphology. From 135 samples collected between 2006 and 2008, 49 species were identified: 25 Chroococcales, 12 Nostocales and 3 Oscillatoriales of Cyanoprokaryota; 3 Chlorellales and 4 Trentepohliales of Chlorophyta and 2 Naviculales of Bacillariophyta. We describe 9 species that are new records for Mexico and all the species found are illustrated as a reference. The ecological valence of the species allows to characterize the flora with affinity to a karst substrate with a basic pH and under fluctuating light, humidity and temperature conditions during the day. Finally, the need to preserve flora and monuments following control strategies based on knowledge of the life cycles of epilithic organisms is pointed out. This is the first study on algae and cyanoprokaryotes in the archaeological zone of Yaxchilan.