|dc.description.abstract||This dissertation aimed to clarify the relative importance of environmental versus human factors in shaping the historic and modern distribution of Polylepis forest in the southern part of the northeastern Cordillera Oriental of Ecuador (491 km2) and to assess the implications of its current distribution range for the genetic variation of the dominant tree species, Polylepis pauta, and for its floristic diversity.
Aerial photography interpretation revealed that Polylepis forest covered approximately 5% percent of the study area in 1956 and that around 3% of that forest cover was lost by 1999 through attrition and shrinkage. Spatial associations between fire, landslides and Polylepis forest loss combined with knowledge of indigenous land use practices, suggests an anthropogenic transition from forest to grassland in the study area. The analysis of allozyme variation from twelve Polylepis forest patches showed that the level of genetic diversity maintained by Polylepis pauta, coupled with low levels of genetic differentiation between populations within and among watersheds, is consistent with a more continuous historical range of the species in the southern part of the northeastern Cordillera Oriental of Ecuador. Results also identify the Oyacachi basin as the richest in P. pauta genetic diversity.
Overall floristic diversity recorded in the Polylepis pauta forest patches sampled in the Chalpi, Oyacachi and Papallacta basins was lower than that observed in floristic inventories of Polylepis forests of Ecuador, Peru and Bolivia. At the local scale, the Oyacachi basin was more diverse than the other two basins. The elevation range spanned by forest patches showed the strongest relationship to plant species diversity. The continuous forest of the Chalpi basin differed from forest fragments in terms of the lower occurrence of ferns and the high frequency of a grass that is indicative of transition from forest to páramo, Neurolepis elata. The virtual absence of N. elata from the other watersheds may be an anthropogenic condition. Phytolith analyses of Polylepis forest species have considerable potential for studies of the historical range of Polylepis forest in the northeastern Cordillera Oriental of Ecuador.||