Resilient diversity, vascular epiphytes in the urban forest of Medellín, Colombia

Urban trees serve as a habitat for vascular epiphytes, yet little is known about how these plant assemblages are structured in highly urbanized tropical cities. We conducted a systematic inventory of vascular epiphytes and nomadic lianas in the urban area of Medellín, Colombia. Epiphytes were surveyed on 600 trees across 60 sites distributed among three urban land-cover categories. In total, we recorded 9,948 individuals representing 48 species and 12 families. Bromeliaceae and Polypodiaceae dominated the assemblages, with Tillandsia recurvata accounting for over 70% of individuals. Vertical stratification, host tree characteristics (e.g., bark texture, tree size), and bark water retention capacity influenced epiphyte abundance and richness. The inner tree crown supported the highest species richness, and rough-barked trees retained more water and hosted more epiphytes. Dispersal mode was a key trait shaping urban assemblages: wind-dispersed species were dominant, while animal-dispersed taxa were rare. Although exotic trees like Fraxinus uhdei were important hosts, epiphyte-host associations were more closely linked to functional tree traits than biogeographic origin. Spatial turnover in species composition was low, reflecting ecological homogenization across the city. Our findings highlight the resilience of a subset of epiphyte species to urban conditions and suggest that urban trees function as biodiversity scaffolds. This study provides baseline data for integrating epiphyte conservation into tropical cities' urban planning and green infrastructure strategies.