Phenology of myxomycetes in Turrialba, Costa Rica

Long-term monitoring and phenological patterns of microbial communities are rare in the scientific literature. Myxomycetes have life cycle characteristics that allow both to be documented. The present study summarizes the integrated floristic and bioclimatic components of a 30-month assessment of myxomycete sporocarps in a premontane tropical forest in Turrialba, Costa Rica. Based on monthly visits and a standard sampling effort of 120 minutes per visit, myxomycetes were recorded on leaves, twigs, and logs on the ground by two to three people in 20-minute periods associated with six different collecting sites within a 34-hectare successional forest patch. Biological data were analyzed using three recorded climatic variables obtained <em>in situ</em> during the complete period of study. Also, the Oceanic Niño Index (ONI), provided by NOAA, an estimate of El Niño-Southern Oscillation (ENSO), was evaluated in the analyses. Overall, 54 species and 2245 records of myxomycetes were recorded, with an average of 14.5 species (range between 6-24) and 78.4 records (range between 20-110) detected each month. In general, neither the number of records nor the number of species were associated with individual climate variables, but multiple regression analyses showed that a combination of the accumulated precipitation of the four days before sampling and the average relative humidity can explain most of the fruiting dynamics (R2 = 0.56). When the ONI index was included in the analyses, the explained variability increased (R2 = 0.64), and when a categorization of months based on the same index was used, analyses showed that both the number of records and species evenness were affected by ENSO. At the species level, <em>Hemitrichia calyculata</em> was the only species observed during every month, closely followed by <em>Arcyria cinerea</em>, <em>A. denudata</em>, and <em>Physarum compressum</em>, recorded on most visits. Sporadic fruiting in some species such as <em>Tubifera microsperma</em>, <em>P. tenerum</em>, <em>P. bogoriense</em>, <em>P. melleum</em>, and <em>Metatrichia vesparia</em> could have been associated with local climate oscillations influenced by ENSO patterns. Phenological patterns were observed at the species level, indicating that in the Neotropics, under favorable conditions, myxomycete sporocarps are practically always present, but species assemblages vary temporally. These variations are primarily driven by local climate, but regional climate dynamics also affect fruiting patterns. Presumably, the remaining ecological effect on fruiting patterns in the Neotropics can be attributed to certain finer factors such as ecosystem structure, substrate quality/ availability, and biotic interactions. As such, phenomena such as climate change can have an important effect on the production of sporocarps by tropical myxomycetes, with subsequent effects of their ecological dynamics.