First steps to study the demography of vascular epiphytes in cities

Abstract

Urban ecosystems could jeopardize the existence of vascular epiphytes (VS), given that their occurrence is linked to phorophyte availability and particular climatic conditions. Despite reports of VS in cities, nothing is known about their demography. A first step in this direction is to describe their population structures (PS). We established the PS of VS present in urban parks in Oaxaca City, addressing the following questions: what is their demographic status? and are there differences in the structure of populations growing in native versus exotic phorophytes? During 2021, we censused all the trees in six urban parks, recording their origin (native or exotic), the epiphytic species found on them and the development stages present in each VS population. Overall, five VS species were documented: Tillandsia ionantha, T. makoyana, T. sp, T. recurvata and T. schiedeana; the first three with only one individual and the latter two with 5,694 and 95, respectively. A MANOVA test indicated significant differences in PS between T. recurvata (type I structure, suggesting a growing population) and T. schiedeana (type III structure, suggesting a senile population) (Wilkes' λ = 0.821, F-Radio = 11.96 P < 0.001). PS showed no differences related to tree origin. Our results indicate that it is necessary to conduct demographic studies to have a more accurate idea of the current condition of vascular epiphytes in cities. For instance, even though we found five VS species, only one of them seems to have viable populations in Oaxaca city.