Inventory and Diversity of Corticolous Lichens on Azadirachta indica (neem) at Three Sites in Berbice, Guyana: A Comparative Study

Lichens are symbiotic organisms composed of fungal and photosynthetic partners, exhibiting unique physiological and ecological traits that allow them to colonize diverse substrates. Azadirachta indica (neem), a fast-growing Meliaceae tree with ecological and medicinal importance, serves as a potential host for corticolous lichen communities; however, systematic studies on lichens inhabiting neem bark are limited. This study investigated lichen diversity, abundance on A. indica across three sites along the East Coast of Berbice, Guyana. A total of ten mature, healthy neem trees were sampled using standardized quadrats (50 × 100 cm) placed at 1.5 m above ground, and lichen species were identified via morphological and chemical spot tests, supported by taxonomic literature. Across all sites, thirteen lichen species representing six families and eight genera were recorded, with total abundance varying from 335 to 743 individuals per site. Parmeliaceae exhibited the highest species richness, with Flavoparmelia soredians and Hypotrachyna laevigata occurring at all sites, whereas species such as Parmelia tiliacea and Flavoparmelia caperta displayed site-specific distributions, indicating differential ecological tolerance and potential sensitivity to microenvironmental factors. Diversity indices (Shannon H′ 1.99-2.04; Simpson SDI 0.80-0.84) suggested moderately high diversity and generally balanced species evenness. Patterns of lichen presence across sites highlight a combination of generalist and host-specific taxa, underscoring the importance of bark characteristics, microclimate, and environmental heterogeneity in shaping epiphytic lichen communities. These findings provide baseline data for lichen biodiversity on neem trees in Guyana and emphasize the potential of A. indica as a host for lichen bioindicator species in monitoring ecosystem health and environmental changes.