Promiscuity in Lichens Follows Clear Rules: Partner Switching in Cladonia Is Regulated by Climatic Factors and Soil Chemistry.

Zuzana Škvorová,Ondřej Peksa,Ivana Černajová,Pavel Škaloud,Patricia Moya,Jana Steinová

doi:10.3389/fmicb.2021.781585

Zuzana Škvorová, Ondřej Peksa + Show 4 more

Open Access

https://doi.org/10.3389/fmicb.2021.781585

Copy DOI

Abstract

Climatic factors, soil chemistry and geography are considered as major factors affecting lichen distribution and diversity. To determine how these factors limit or support the associations between the symbiotic partners, we revise the lichen symbiosis as a network of relationships here. More than one thousand thalli of terricolous Cladonia lichens were collected at sites with a wide range of soil chemical properties from seven biogeographical regions of Europe. A total of 18 OTUs of the algal genus Asterochloris and 181 OTUs of Cladonia mycobiont were identified. We displayed all realized pairwise mycobiont–photobiont relationships and performed modularity analysis. It revealed four virtually separated modules of cooperating OTUs. The modules differed in mean annual temperature, isothermality, precipitation, evapotranspiration, soil pH, nitrogen, and carbon contents. Photobiont switching was strictly limited to algae from one module, i.e., algae of similar ecological preferences, and only few mycobionts were able to cooperate with photobionts from different modules. Thus, Cladonia mycobionts generally cannot widen their ecological niches through photobiont switching. The modules also differed in the functional traits of the mycobionts, e.g., sexual reproduction rate, presence of soredia, and thallus type. These traits may represent adaptations to the environmental conditions that drive the differentiation of the modules. In conclusion, the promiscuity in Cladonia mycobionts is strictly limited by climatic factors and soil chemistry.

Highlights

IntroductionWe regard lichens as complex ecosystems (Hawksworth and Grube, 2020) consisting of a mostly ascomycete fungal partner, one or more photobionts (algal and/or cyanobacterial), bacterial communities (Uphof, 1925; Grube et al, 2009; Bates et al, 2011), and potentially basidiomycete yeasts (localized primarily in the thallus cortex) (Spribille et al, 2016) and lichenicolous fungiPromiscuity in Lichens Follows Clear Rules and other lichen-inhabiting organisms (Arnold et al, 2009)
At present, we regard lichens as complex ecosystems (Hawksworth and Grube, 2020) consisting of a mostly ascomycete fungal partner, one or more photobionts, bacterial communities (Uphof, 1925; Grube et al, 2009; Bates et al, 2011), and potentially basidiomycete yeasts (Spribille et al, 2016) and lichenicolous fungiPromiscuity in Lichens Follows Clear Rules and other lichen-inhabiting organisms (Arnold et al, 2009)
How are the symbiotic trade-offs resolved, and what factors play an important role in limiting the algal-fungal promiscuity? In accordance with previous studies (Wirtz et al, 2003; Leavitt et al, 2015, Singh et al, 2017), our results confirm that the lichen association does not represent a strictly specific relationship

Summary

Introduction

We regard lichens as complex ecosystems (Hawksworth and Grube, 2020) consisting of a mostly ascomycete fungal partner, one or more photobionts (algal and/or cyanobacterial), bacterial communities (Uphof, 1925; Grube et al, 2009; Bates et al, 2011), and potentially basidiomycete yeasts (localized primarily in the thallus cortex) (Spribille et al, 2016) and lichenicolous fungiPromiscuity in Lichens Follows Clear Rules and other lichen-inhabiting organisms (Arnold et al, 2009). The main role in dispersion, colonization abilities, and environmental preferences is played by the first two above-mentioned partners: the fungal mycobiont and its main associated photobiont. Such symbiosis is not strictly specific, and the coevolution between the involved partners is limited (Rikkinen, 2003; Lücking et al, 2009; Thüs et al, 2011). Except for some intracellular interactions (Nowack et al, 2016) or the green hydra (Hydra viridissima) symbiosis (Kawaida et al, 2013), most symbiotic organisms show low specificity in some life phases or in extreme conditions (Beck, 2002; Osyczka et al, 2021; Rola et al, 2021), forming a symbiotic relationship with a variety of partners. It is worth noting that the symbiotic interactions are tremendously widespread in nature, and we can find examples of specificity levels at both ends of the spectrum

Objectives

Methods

Results

Discussion

Conclusion