Few large or many small offspring? Familiar dilemma now demonstrated also in wood-inhabiting fungi

Veera Norros, Panu Halme, Anna Norberg, Otso Ovaskainen

This is a plain language summary of a Functional Ecology research article which can be found here.

The number of offspring within a given time is one of the most fundamental traits of an organism. It determines how fast populations can grow, adapt to new conditions and spread to new areas. The number of offspring is also closely linked to other features of the organism’s lifestyle. For example, it has long been established for animals and plants that there is a trade-off between the number and size of offspring – comparing across species, when offspring size increases, their number decreases. For fungi, however, life history traits are poorly known, and it has rarely been possible to demonstrate such general patterns.

Spore production was measured by allowing spores to settle on a piece of plastic foil pinned to the fruit body (here Phellinus tremulae) (credit: Panu Halme)

To address this question in one group, fungi that decay dead wood or are parasitic on live trees, we monitored the rate of spore production in 97 species at a boreal forest site in Central Finland. We found that species differ in their seasonality: some species sporulate mostly in the spring, others in the summer or autumn. This can create large differences in how their spores can colonize new habitat patches, as the weather conditions and the conditions for spore germination and mycelial growth can vary markedly between seasons. We also discovered a strong trade-off between spore number and size, with each species dividing roughly the same total spore volume in smaller or larger spores. These results give new insight into the life history strategies of fungi, which can help predict how different species will respond to the increasingly severe threats of habitat loss and climate change.


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