Combining metagenomics with fruit-body surveys reveals contrasting life-history strategies in fungi

In fungi, fruit bodies are often easily surveyed in the field, whereas research on mycelial growth and competition has been mostly confined to laboratory studies. As a consequence, the link between mycelial processes and patterns of species occurrence are generally poorly understood under natural conditions. Here we combine high throughput sequencing with a conventional fruit body inventory to study simultaneously the mycelial and fruit body stages in a community of fungi inhabiting dead wood. We studied the mycelial stage by extracting DNA from saw dust samples followed by 454 sequencing of the ITS1 and ITS2 regions and an automated procedure for species identification. The correlation between fruit body occurrence and mycelial abundance was high, suggesting that the saw dust samples were well able to represent the dominating fungal communities within the logs. The species present as mycelia showed marked variation in their overall rate of fruiting, as well as in the time delay from mycelial colonization until formation of fruit bodies. In this species community, earlier studies based on fruit body inventories have shown that loss of dead wood and forest fragmentation have led to a disproportionally high decline in those species that have highly specialized resource requirements. In this paper, we show that this pattern may be less pronounced in the mycelial stage, as the highly specialized species have a longer time delay from mycelial colonization until fruit body formation and an overall lower fruiting rate than the generalist species.