Fungal spore diversity reflects substrate-specific deposition challenges

Sara Calhim,Jacob Heilmann-Clausen,Panu Halme,Claus Bässler,Thomas Læssøe,Jens H Petersen

doi:10.1038/s41598-018-23292-8

Abstract

Sexual spores are important for the dispersal and population dynamics of fungi. They show remarkable morphological diversity, but the underlying forces driving spore evolution are poorly known. We investigated whether trophic status and substrate associations are associated with morphology in 787 macrofungal genera. We show that both spore size and ornamentation are associated with trophic specialization, so that large and ornamented spores are more probable in ectomycorrhizal than in saprotrophic genera. This suggests that spore ornamentation facilitates attachment to arthropod vectors, which ectomycorrhizal species may need to reach lower soil layers. Elongated spore shapes are more common in saprotrophic taxa, and genera associated with above ground substrates are more likely to have allantoid (curved elongated) spores, probably to lower the risk of wash out by precipitation. Overall, our results suggest that safe arrival on specific substrates is a more important driver of evolution in spore morphology than dispersal per se.

Highlights

Dispersal plays a major role in the population dynamics of almost all organisms, and may, depending on the organism, involve mature individuals as well as dedicated dispersal propagules such as pollen, seeds and spores[1,2]
These external factors may be subject to co-evolutionary forces, as in the case of fungi associating with specific animal dispersal vectors[9,10], but in the majority of cases only the dispersal propagules are subject to evolution
In this paper we investigate the links between spore morphology, trophic status and substrate preference in 781 fungal genera divided across the two major fungal phyla that produce fruit bodies, i.e. Ascomycota and Basidiomycota

Summary

Introduction

Dispersal plays a major role in the population dynamics of almost all organisms, and may, depending on the organism, involve mature individuals as well as dedicated dispersal propagules such as pollen, seeds and spores[1,2]. The transport and deposition stages of dispersal are mainly driven by external factors including wind, water-currents, precipitation, animal vectors and habitat surface features affecting attachment[4,7,8]. If biotic, these external factors may be subject to co-evolutionary forces, as in the case of fungi associating with specific animal dispersal vectors[9,10], but in the majority of cases only the dispersal propagules are subject to evolution. Evolution may affect several traits that affect dispersal success during transport and deposition phases, e.g. the size and morphology of the dispersal propagules[11]. Log[10] Spore volume λ Intercept Trophic status Ornamentation α Intercept Trophic status Allantoid shape α Intercept Trophic status Globose shape α Intercept Trophic status Cylindrical shape α Intercept Trophic status Elongated shape α Intercept Trophic status

Methods

Results

Discussion

Conclusion