Cryptic Biodiversity of Arid-Land Fungi: Fungal Associates of Biocrusts, Lichens and Plants

Abstract

Organisms in arid and semi-arid lands face environmental challenges such as heat and drought, high salinity and low organic content of soils, and intense ultraviolet radiation. Despite these challenges, dryland environments are some of the most biologically diverse ecosystems in the world: plants that inhabit these ecosystems have evolved unique ways to combat these challenges through distinctive adaptations and, in some cases, symbiotic associations that enhance their resilience. Little work has been done to characterize the fungal lineages that occur as cryptic symbionts of plants in dryland environments. This thesis focuses specifically on characterizing fungi that occur within photosynthetic structures – leaves, lichen thalli, and biological soil crusts – collected from arid and semi-arid environments. In my first chapter I characterize fungi associated with biological soil crusts in the southwestern United States, focusing on their responses to disturbance at the Santa Rita Experimental Range in Arizona. In my second chapter, I contribute novel data regarding culturable endophytes of lichens and plants in southwestern Africa, and place these into a global context by relating their diversity and composition to climate variables across three continents. Taken together, my work showcases the diversity of fungi that exists within these ecosystems and provides insight into how the distributions of fungi and their hosts may shift in response to changes, such as those associated with land-use, disturbance, and ultimately, climate change.