Chapter 1 - Aquatic hyphomycete spores: What do we know, where do we go from here?

Abstract

Headwater streams, especially those flowing through forested landscapes, are mainly detritus-based systems. The interactions between leaf litter, microbial decomposers and invertebrate detritivores set the course for the vital carbon flow in these ecosystems. Among the microbial decomposers, fungi, particularly aquatic hyphomycetes (AQHs) are the primary mediators of carbon and nutrient flow across food webs. AQHs channel ≥ 50% of their production in releasing a prodigious number of asexual spores (conidia) directly from the leaf litter into the water. Spores can be used as proxies for Darwinian fitness, ensuring dispersal and representation in the next generation. They are also critical constituents of fine particulate organic matter serving, potentially, as food for filter feeders and collectors, two important functional invertebrate groups. Yet to date, the role of AQH spores in the energy pathway in streams has rarely been explored. Here we discuss what progress has been made in exploring spores as a fundamental aspect of AQH research. We hope to point out potential blind spots in stream ecology and to stimulate research on the functions of spores in forested streams. This chapter articulates unresolved pivotal aspects such as biodiversity and biogeography of spores, environmental cues for their production, germination and viability, and their role as carriers of essential molecules in streams. Addressing these issues should allow ecologists to deepen their knowledge of ecosystem functioning across the globe and help manage vulnerable ecosystems.