FUNGI IN A WARMER WORLD: PALEOCLIMATE RECONSTRUCTION AND FUNGAL GUILD CHANGES ACROSS THE MIOCENE CLIMATE OPTIMUM

Since the first state of the world’s fungi report in 2018, understanding of how fungal communities are impacted by climate and environmental change has increased significantly, including how guild structures respond to perturbations. It is known, for example, that ecosystem disturbances, such as deforestation, can lead to increases in saprophytic fungi at the expense of mycorrhizal fungi, especially ectomycorrhizal fungi. Warming also leads to changes, including increases in plant pathogens, and, potentially, decreases in ectomycorrhizal fungi, which tend to have narrower climatic tolerances than other guilds. Tracking changes in fungal assemblages across the Miocene Climate Optimum (MCO) and examining the fossil record of fungal guild dynamics as preserved in changing depositional environments are two of the primary goals of the Fungi in a Warmer World project. Fungal distributions are driven in part by plant distributions, and both tend to track climate space shifts. In the fossil record, this is most easily seen at the assemblage-scale; larger assemblages of identified taxa result in better reconstructions of climate space shifts than smaller assemblages. Guild structural variations can be challenging to examine, as preservation of non-melanized spores is highly variable and tends to be much lower, overall, than that of melanized spores, thus large portions of the record, especially of the very important ectomycorrhizal fungi, are missing. That said, shifts of varying magnitudes in the relative diversity of saprotrophs, parasites, endophytes, and soil fungi can be seen in multiple locations globally during the MCO, including the multiple sites in the contiguous United States, Peru, Colombia, Argentina, Nigeria, Kenya, the UK, Denmark, Slovakia, Thailand, southeastern China, and southeastern Australia, and in multiple depositional environments, from peat-producing to lacustrine to fluvial to coastal. Here we present a synthesis of fungal and plant climate space shift records across the MCO, for the first time alongside sample-by-sample analyses of guild structural variations relative to changing environments.