Lichen morphospecies diversity and community composition across the Tswalu Kalahari Reserve, South Africa

• This project represents the first study of lichens at the Tswalu Kalahari Reserve. • 49 morphospecies occur across four localities. • Crustose growth forms, green algal photobionts, and sexual reproductive structures were the most commonly observed traits. • Diversity and community composition differed across distinct sites and substrates. • Environmental variables did not conclusively explain differences in diversity. The Tswalu Kalahari Reserve in the Northern Cape Province of South Africa has no previously published data on its lichen biota, which reflects the broader status of lichenology in South Africa. It is estimated that nearly half of the country's lichen species remain undescribed. Consequently, this study aimed to gather baseline data on lichen diversity and distribution across the reserve. We quantified morphological and functional diversity, characterized lichen communities, and analyzed relationships between lichen diversity and environmental variables (northness, coverage, elevation, insolation, site, substrate type, and substrate texture) using morphospecies concepts. We documented 49 morphospecies across three habitats in the Tswalu Kalahari Reserve, including at least one species that is new to science ( Caloplaca tswaluensis Fryday, S. Svoboda & D. A. Ward; Fryday et al. in press) and another ( Trapeliopsis glaucolepidea (Nyl.) Gotth. Schneid.) that had not previously been reported from Africa. Overall, we recorded lower diversity in corticolous (bark dwelling) lichen communities compared to saxicolous (rock dwelling) lichen communities. However, we did not find a significant effect of any measured environmental variable on saxicolous species richness. This preliminary study underscores the need for further investigation of the diverse, unrecorded lichen diversity that likely exists in other areas of the country as well as the differences in lichen communities on bark and rock substrates. This study also shows that morphospecies concepts can be informative and accessible approaches for exploratory lichen studies, particularly in regions with relatively understudied cryptogam communities.