Phenology is the timing of a species life history events. Fungal phenology is dependent on its ecology and climatic factors such as rainfall and temperature. Over time, species fine tune their phenology which ultimately enhances their ability to access resources and reproduce. In a paper published in Fungal Ecology, Dr. Meike Piepenbring and her team spent two years in southwestern Panama to better understand the phenology of two ecological types of fungi. The phenology of saprobic (decomposer) Agaricales, and foliar pathogenic fungi followed different patterns as the quantity of their resources differed throughout the year. Learning about seasonal timing in Panama was as appealing as it was mystifying, because areas closer to the equator experience just two seasons-wet and dry. Living in a temperate location, I am used to four seasons so the fungal phenology I grew up with is quite different. Still, this paper offered great ecological insight applicable to all forest floor communities, because the dynamism of these seperate ecosystems is still shaped by the timing of different species.
For saprobic fungi, their seasonal timing is most dependent on moisture content. Deciduous plants in these regions drop their leaves with the onslaught of the dry season to help conserve water. For fungi that rely on fallen plant tissue, synchronist leaf fall events provide them with an enormous resource influx. Though, these resources can’t be metabolized without an adequate water supply. For this reason, fruiting bodies only appear once the rainy season begins. The beginning of the rainy season is when you find the most saprobic fungi in southwestern Panama, with their occurrence declining throughout the duration of the rainy season. Goldilocks principle is at play here, as the torrential rains wash and weather away the plant material along with their nutrients. Fruiting bodies are still seen throughout the duration of the rainy season but only truly manifest during short periods of drought called “veranillo”. The soaking rains hinder fungal growth further as the wet conditions promote molds that parasitize mushrooms. Together, these factors have shaped saprobic species of fungi to fruit in the early part of the rainy season.
Fungi that parasitize leaf tissue follow a different phenology. The leaves of deciduous trees form in the beginning of the rainy season, when water availability stimulates the reactions involved with photosynthesis. Pathogenic fungi that find refugium in living evergreen leaves can spread to newly produced leaves. These parasites are sensitive to dry conditions and only persist throughout the dry season on evergreen leaves because they remain tapped into the water supply of the host plant. Although young leaves are more vulnerable to herbivory, they are quite adequate at defending themselves from pathogenic fungi. Foliar parasites become prominent in the middle of the rainy season when plants absorb defensive compound in mature leafs to re-allocate them to younger leaves. Foliar parasites are less common at the end of the rainy season for several reasons. Drenching rains wash away fungal structures, promote other parasites and epiphytes that compete for space and nutrients, and enhance herbivorous insect species. With all of these ecological dynamics, foliar parasites are most dominant in the middle of the rainy season.
Even if what I just learned takes place in southwestern Panama, I can gain insight to these biological configurations and apply them to the habitats around me. The quest for ecological comprehension doesn’t end once I identify a species. I need to know its phenology. A species ecological timing helps me gauge its function relative to the forest floor. Phenology drives species interactions and once understood, helps me better understand the patterns I see in nature.