Abstract
The ecological significance of fungi occurring asymptomatically inside living plant leaves is poorly understood. Given the broad saprotrophic potential of many endophytic fungi, we hypothesized that they persist in decaying litter for an extended period of time after leaf abscission. Fungal assemblages were assessed by high-throughput sequencing in autumn leaves of beech (Fagus sylvatica) and in the corresponding leaf litter in 388 samples from 22 beech forest plots in three widely distant regions of Germany. A considerable proportion of the leaf-endophytic fungi was also found in 1-year-old litter. Co-occurrence networks revealed that the fungi formed unstructured assemblages inside the living leaves, rather than well-structured communities. Previously endophytic fungi constituted an integral part of the fungal litter community and were by far the most active fungi in 1-year-old litter. We therefore consider these endophytic occurrences to represent transient stages. Composition of the aboveground microbiome appears therefore to be closely connected to the process of litter decomposition. Considering the respective linked fungal habitat will facilitate predicting nutrient and carbon cycling and storage in forest ecosystems as well as elucidating the ecology of leaf microbiomes.
Highlights
All macroorganisms are associated with microorganisms, the so-called microbiome
Fungal assemblages were assessed by highthroughput sequencing in autumn leaves of beech (Fagus sylvatica) and in the corresponding leaf litter in 388 samples from 22 beech forest plots in three widely distant regions of Germany
Composition of the aboveground microbiome appears to be closely connected to the process of litter decomposition
Summary
All macroorganisms are associated with microorganisms, the so-called microbiome. The microbiome has been shown to affect morphology, physiology, development, behaviour, health, immunology, reproduction and fitness of the host organisms (Rosenberg and Zilber-Rosenberg 2016). The holobiont, i.e. the macroorganism with its associated microbiome (Margulis and Fester 1991; Rohwer et al 2002; Zilber-Rosenberg and Rosenberg 2008), was suggested to represent the unit to be considered in ecological and evolutionary contexts (Hawksworth 1991). The aboveground microbiome includes a huge diversity of fungi, the majority of which is shared among host individuals and species (Saikkonen 2007; Rodriguez et al 2009; Suryanarayanan et al 2003; Suryanarayanan 2011, Sun et al 2012), even though the aboveground plant organs are physically disconnected.
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