Abstract
Phenotypic plasticity of traits is commonly measured in plants to improve understanding of organismal and ecosystem responses to climate change but is far less studied for microbes. Specifically, decomposer fungi are thought to display high levels of phenotypic plasticity and their functions have important implications for ecosystem dynamics. Assessing the phenotypic plasticity of fungal traits may therefore be important for predicting fungal community response to climate change. Here, we assess the phenotypic plasticity of 15 fungal isolates (12 species) from a Southern California grassland. Fungi were incubated on litter at five moisture levels (ranging from 4–50% water holding capacity) and at five temperatures (ranging from 4–36 °C). After incubation, fungal biomass and activities of four extracellular enzymes (cellobiohydrolase (CBH), β-glucosidase (BG), β-xylosidase (BX), and N-acetyl-β-D-glucosaminidase (NAG)) were measured. We used response surface methodology to determine how fungal phenotypic plasticity differs across the moisture-temperature gradient. We hypothesized that fungal biomass and extracellular enzyme activities would vary with moisture and temperature and that the shape of the response surface would vary between fungal isolates. We further hypothesized that more closely related fungi would show more similar response surfaces across the moisture-temperature gradient. In support of our hypotheses, we found that plasticity differed between fungi along the temperature gradient for fungal biomass and for all the extracellular enzyme activities. Plasticity also differed between fungi along the moisture gradient for BG activity. These differences appear to be caused by variation mainly at the moisture and temperature extremes. We also found that more closely related fungi had more similar extracellular enzymes activities at the highest temperature. Altogether, this evidence suggests that with global warming, fungal biodiversity may become increasingly important as functional traits tend to diverge along phylogenetic lines at higher temperatures.
Highlights
Few trait-based approaches in soil microbial ecology assess phenotypic plasticity as a trait [1, 2]
Phenotypic plasticity is commonly studied in plants to improve understanding of organismal and ecosystem responses to climate change [4,5,6,7], yet far less studied in microbes [2, 8]
We focused on potential enzyme activity (EEA) and fungal biomass because they are sensitive to changes in temperature and moisture [42,43,44] and have implications for biogeochemical cycling [45, 46]
Summary
Few trait-based approaches in soil microbial ecology assess phenotypic plasticity as a trait [1, 2]. Organisms with high phenotypic plasticity exhibit a wide range of physiological or morphological changes in response to different environmental conditions [3]. Phenotypic plasticity is commonly studied in plants to improve understanding of organismal and ecosystem responses to climate change [4,5,6,7], yet far less studied in microbes [2, 8]. Decomposer fungi, for example, play a critical role in the global carbon (C) and nitrogen (N) cycling [15]. If these fungi have high phenotypic plasticity, they could quickly alter ecosystem dynamics by changing soil properties and rates of nutrient cycling [16, 17]. Phenotypic plasticity is important to consider when predicting organismal responses to climate change [2, 25]
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