Lichens as indicators of environmental quality in southern Brazil: An integrative approach based on community composition and functional parameters

Abstract

Lichens are widely used to assess the consequences of human activities, including urbanization, which has strong influence on the structure of their communities. Our hypothesis is that increasing human population density and modifying land use and cover cause structural and functional changes in lichen communities. The main objective of this study was to evaluate changes in lichen species composition and functional patterns along a gradient of urbanization in southern Brazil. The study was carried out in nine sites, classified a priori according to the matrix where they were inserted, as rural, suburban and urban, in which the lichen community was sampled in 10 phorophytes using the rubber band method. Several environmental variables and lichen functional traits were quantified. The sites inserted in the rural matrix were characterized by phorophytes with higher bark pH, higher percentage of agriculture areas in the vicinity of the sampling sites, and by the following functional groups: loosely attached crustose thalli, Trentepohlia photobiont, reproduction by thallus fragmentation and apothecia. The sites located in the urban matrix showed greater demographic density, vehicular fleet, percentage of urban and open fields coverage, foliose narrow lobed thalli, photobiont Chlorococcoid algae and reproduction by soredia. Regarding lichen functional patterns, sites located in the rural matrix presented higher species richness, functional richness, evenness and diversity. Based on our results, we showed that urbanization has a strong influence on lichen communities, since it has affected both species composition and functional patterns, besides species richness. The combined use of species composition, richness, functional composition and functional indexes proved to be effective in obtaining detailed information on the changes suffered by lichen communities and can be used as a tool to evaluate the environmental quality in urban environments.