Trade-Offs Between Growth Rate and Other Fungal Traits

Abstract

If we better understand how fungal responses to global change are governed by their traits, we can improve predictions of fungal community composition and ecosystem function. Specifically, we can examine trade-offs among traits, in which the allocation of finite resources toward one trait reduces the investment in others. We hypothesized that trade-offs among fungal traits relating to rapid growth, resource capture, and stress tolerance sort fungal species into discrete life history strategies. We used the Biolog Filamentous Fungi database to calculate maximum growth rates of 37 fungal species and then compared them to their functional traits from the funfun database. In partial support of our hypothesis, maximum growth rate displayed a negative relationship with traits related to resource capture. Moreover, maximum growth rate displayed a positive relationship with amino acid permease, forming a putative Fast Growth life history strategy. A second putative life history strategy is characterized by a positive relationship between extracellular enzymes, including cellobiohydrolase 6, cellobiohydrolase 7, crystalline cellulase AA9, and lignin peroxidase. These extracellular enzymes were negatively related to chitosanase 8, an enzyme that can break down a derivative of chitin. Chitosanase 8 displayed a positive relationship with many traits that were hypothesized to cluster separately, forming a putative Blended life history strategy characterized by certain resource capture, fast growth, and stress tolerance traits. These trait relationships complement previously explored microbial trait frameworks, such as the Competitor-Stress Tolerator-Ruderal and the Yield-Resource Acquisition-Stress Tolerance schemes.

Ecological strategies of microbes: Thinking outside the triangle

“…When the ‘bottom up’ studies tested for trait clustering without a priori assignments to ecological strategies, Ruderal traits tended cluster separately from a variety of ecological strategies: high growth temperature, resource acquisition, blended and versatility (Figure 2; Lovero & Treseder, 2021; Westoby et al, 2021). In other words, fast maximum growth appears to frequently trade‐off with other traits.…”

“…Versatility may be worth adding to the CSR and YAS schemes. Finally, Lovero and Treseder (2021) analysed functional genes and growth rates of 37 fungal isolates, traits based on functional genes and growth rate tended to form three clusters: fast growth, resource capture and a blended strategy containing resource capture, stress tolerance and ruderal traits. In fact, in that study, the CSR framework did not significantly explain relationships between traits (Lovero & Treseder, 2021).…”

“…Finally, Lovero and Treseder (2021) analysed functional genes and growth rates of 37 fungal isolates, traits based on functional genes and growth rate tended to form three clusters: fast growth, resource capture and a blended strategy containing resource capture, stress tolerance and ruderal traits. In fact, in that study, the CSR framework did not significantly explain relationships between traits (Lovero & Treseder, 2021). Overall, the three ecological strategies of the CSR framework were generally well supported, and so were a few other strategies that are broadly related to environmental preferences.…”

“…For each study, I used the authors' classifications of traits associated with each ecological strategy (Table 1). Two studies used the ‘bottom‐up’ approach of identifying traits that tend to coincide within taxa without a priori decisions about expected ecological strategies (Lovero & Treseder, 2021; Westoby et al, 2021). I recorded these putative ecological strategies as well.…”

“…Another example is extracellular enzyme production, which we assess by measuring the breakdown of model substrates, not necessarily actual enzyme substrates (German et al, 2011; Wallenstein & Weintraub, 2008). Growth rate is often measured under laboratory conditions (Lennon et al, 2012; Lovero & Treseder, 2021; Novak et al, 2006; Ramin & Allison, 2019; Westoby et al, 2021), which might not reflect environmental conditions in the field.…”