Palynological indicators for assessing ecological continuity in the tropical montane cloud forest of Mexico

Local pollen represents a crucial paleoecological approach for monitoring the historical legacy of eastern Mexico’s tropical montane cloud forests (TMCF), which are often shrouded in cloud or mist, although few studies have explored this area. This paper presents a taxonomic selection of local indicators from 48 sites across 12 altitudinal gradients in three forest patches subjected to varying tree cover loss, collected from moss polsters. Using Principal Component Analysis, we identified three zones based on their levels of disturbance, with the goal of determining traits of pollen grains and floral phenology that influence habitat differentiation. Then, we identified four potential categories to evaluate historical legacies (anthropogenic pressures): (a) habitat-specialist tree taxa, (b) specialized entomophilous taxa, (c) anemophilous pollen with a short dispersal range, and (d) disturbance taxa. Our results suggest that genera such as Bejaria, Clethra, Fagus, Juniperus, Magnolia, Zanthoxylum, Zea mays, and five plant families are significant for these paleoenvironments. Following the literature, we discuss the implications of our pollen indicators in evaluating different ecological thresholds, such as ecological resilience and the loss of functional diversity. For these purposes, some traits and attributes of pollen systematics and floral phenology are crucial to long-term habitat persistence. We conclude that our local indicators for persistent montane forests can be added to other studies concerning the ecological continuity of the TMCF.