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Abstract PremiseSouthern Africa is a biodiversity hotspot rich in endemic plants and lichen‐forming fungi. However, species‐level data about lichen photobionts in this region are minimal. We focused onTrebouxia(Chlorophyta), the most common lichen photobiont, to understand how southern African species fit into the global biodiversity of this genus and are distributed across biomes and mycobiont partners. MethodsWe sequencedTrebouxianuclear ribosomal ITS andrbcLof 139 lichen thalli from diverse biomes in South Africa and Namibia. GlobalTrebouxiaphylogenies incorporating these new data were inferred with a maximum likelihood approach.Trebouxiabiodiversity, biogeography, and mycobiont–photobiont associations were assessed in phylogenetic and ecological network frameworks. ResultsAn estimated 43 putativeTrebouxiaspecies were found across the region, including seven potentially endemic species. Only five clades represent formally described species:T. arboricolas.l. (A13),T. cf.cretacea(A01),T. incrustata(A06),T. lynniae(A39), andT. maresiae(A46). Potential endemic species were not significantly associated with the Greater Cape Floristic Region or desert.Trebouxiaspecies occurred frequently across multiple biomes. Annual precipitation, but not precipitation seasonality, was significant in explaining variation inTrebouxiacommunities. Consistent with other studies of lichen photobionts, theTrebouxia–mycobiont network had an anti‐nested structure. ConclusionsDepending on the metric used, ca. 20–30% of globalTrebouxiabiodiversity occurs in southern Africa, including many species yet to be described. With a classification scheme forTrebouxianow well established, tree‐based approaches are preferable over “barcode gap” methods for delimiting new species. 

ABSTRACT Diplosphaera chodatii,a unicellular terrestrial microalga found either free-living or in association with lichenized fungi, protects itself from desiccation by synthesizing and accumulating low-molecular-weight carbohydrates such as sorbitol. The metabolism of this algal species and the interplay of sorbitol biosynthesis with its growth, light absorption, and carbon dioxide fixation are poorly understood. Here, we used a recently available genome assembly forD. chodatiito develop a metabolic flux model and analyze the alga’s metabolic capabilities, particularly, for sorbitol biosynthesis. The model contains 151 genes, 155 metabolites, and 194 unique metabolic reactions participating in 12 core metabolic pathways and five compartments. Both photoautotrophic and mixotrophic growths ofD. chodatiiwere supported by the metabolic model. In the presence of glucose, mixotrophy led to higher biomass and sorbitol yields. Additionally, the model predicted increased starch biosynthesis at high light intensities during photoautotrophic growth, an indication that the “overflow hypothesis—stress-driven metabolic flux redistribution” could be applied toD. chodatii. Furthermore, the newly developed metabolic model ofD. chodatii, iDco_core, captures both linear and cyclic electron flow schemes characterized in photosynthetic microorganisms and suggests a possible adaptation to fluctuating water availability during periods of desiccation. This work provides important new insights into the predicted metabolic capabilities ofD. chodatii, including a potential biotechnological opportunity for industrial sorbitol biosynthesis.IMPORTANCELichenized green microalgae are vital components for the survival and growth of lichens in extreme environmental conditions. However, little is known about the metabolism and growth characteristics of these algae as individual microbes. This study aims to provide insights into some of the metabolic capabilities ofDiplosphaera chodatii, a lichenized green microalgae, using a recently assembled and annotated genome of the alga. For that, a metabolic flux model was developed simulating the metabolism of this algal species and allowing for studying the algal growth, light absorption, and carbon dioxide fixation during both photoautotrophic and mixotrophic growth,in silico. An important capability of the new metabolic model ofD. chodatiiis capturing both linear and cyclic electron flow mechanisms characterized in several other microalgae. Moreover, the model predicts limits of the metabolic interplay between sorbitol biosynthesis and algal growth, which has potential applications in assisting the design of bio-based sorbitol production processes. 

ABSTRACT We present six whole community shotgun metagenomic sequencing data sets of two types of biological soil crusts sampled at the ecotone of the Mojave Desert and Colorado Desert in California. These data will help us understand the diversity and function of biocrust microbial communities, which are essential for desert ecosystems. 

Abstract Recent human activity has profoundly transformed Earth biomes on a scale and at rates that are unprecedented. Given the central role of symbioses in ecosystem processes, functions, and services throughout the Earth biosphere, the impacts of human-driven change on symbioses are critical to understand. Symbioses are not merely collections of organisms, but co-evolved partners that arise from the synergistic combination and action of different genetic programs. They function with varying degrees of permanence and selection as emergent units with substantial potential for combinatorial and evolutionary innovation in both structure and function. Following an articulation of operational definitions of symbiosis and related concepts and characteristics of the Anthropocene, we outline a basic typology of anthropogenic change (AC) and a conceptual framework for how AC might mechanistically impact symbioses with select case examples to highlight our perspective. We discuss surprising connections between symbiosis and the Anthropocene, suggesting ways in which new symbioses could arise due to AC, how symbioses could be agents of ecosystem change, and how symbioses, broadly defined, of humans and “farmed” organisms may have launched the Anthropocene. We conclude with reflections on the robustness of symbioses to AC and our perspective on the importance of symbioses as ecosystem keystones and the need to tackle anthropogenic challenges as wise and humble stewards embedded within the system. 

ABSTRACT Sloths are unusual mobile ecosystems, containing a high diversity of epibionts living and growing in their fur as they climb slowly through the canopies of tropical forests. These epibionts include poorly studied algae, arthropods, fungi, and bacteria, making sloths likely reservoirs of unexplored biodiversity. This review aims to identify gaps and eliminate misconceptions in our knowledge of sloths and their epibionts, and to identify key questions to stimulate future research into the functions and roles of sloths within a broader ecological and evolutionary context. This review also seeks to position the sloth fur ecosystem as a model for addressing fundamental questions in metacommunity and movement ecology. The conceptual and evidence‐based foundation of this review aims to serve as a guide for future hypothesis‐driven research into sloths, their microbiota, sloth health and conservation, and the coevolution of symbioses in general. 

The public perception of viruses has historically been negative. We are now at a stage where the development of tools to study viruses is at an all-time high, but society’s perception of viruses is at an all-time low. The literature regarding viral interactions has been skewed towards negative (i.e., pathogenic) symbioses, whereas viral mutualisms remain relatively underexplored. Viral interactions with their hosts are complex and some non-pathogenic viruses could have potential benefits to society. However, viral research is seldom designed to identify viral mutualists, a gap that merits considering new experimental designs. Determining whether antagonisms, mutualisms, and commensalisms are equally common ecological strategies requires more balanced research efforts that characterize the full spectrum of viral interactions.