Master of Science (MS)


Biological Sciences

Document Type



The cloud forest sugar maple, Acer saccharum subsp. skutchii, occurs as five disjunct populations, four in Mexico and one in Guatemala. I assessed the current status, distribution, and environmental relations of forests containing these populations, and I compared the species composition of these forests with other temperate and cloud forests in North and Central America. I gave special emphasis to a recently discovered population in Talpa de Allende, Jalisco, Mexico, by assessing its tree richness and generic composition in a continental context. In the five studied cloud forest sugar maple populations, basal area of all trees ¡Ý1 cm DBH varied between 25.7-52.2 m2ha-1, and density ranged from 990-2929 trees per ha. A. saccharum subsp. skutchii represented 7-43% of the total basal area and 1-16% of the tree stems. Bray & Curtis ordination of cloud forest sugar maple populations indicated that most of the variation in relative tree abundance could be explained by soil characteristics and presence of canopy gaps. More cloud forest sugar maples occurred in sites with higher soil moisture (r=0.716). In contrast, a NMS ordination indicated that the majority of the variance in community composition of all temperate and cloud forests analyzed was related to latitude, elevation, and precipitation. Tree species richness of Talpa de Allende and 14 other temperate and cloud forests around the world was significantly different (F=27.53, p=<0.0001). Species richness of forest in Asia and Talpa de Allende did not differ. In addition, generic composition was similar for forests in Asia and Talpa. Based on NMS ordination and Ward&39;s classification, I hypothesize that six forest sites in Jalisco, Tamaulipas, Veracruz, and Hidalgo (Mexico) contain a unique and ancient flora, were connected and shared species before the Pleistocene, and currently function as tree refuges of that ancient flora. Based on the limited distribution of cloud forest sugar maple and its small number of extant populations I propose the inclusion of A. saccharum subsp. skutchii in the IUCN Red List Catalog and as Endangered in the Guatemalan Species Red List. In addition, I propose the creation of a 56,394.9 ha Biosphere Reserve in Talpa de Allende.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

William J. Platt