Myxomycete assemblage turnover across a moisture and elevation gradient in Costa Rica

The formation of sporocarps in myxomycetes depends on environmental characteristics, among which, moisture and temperature seem to be relevant in tropical areas. Since temperature is linked to elevation, the effect of both of these variables can be studied along a natural moisture and elevation gradient. In the present study, myxomycete assemblages associated with three forest types representing a natural gradient of both climatic characteristics were studied during the same season in consecutive years. Species richess was higher in the driest studied locations and a clear separation among myxomycete assemblages across the gradient was documented. Such separation, however, highly likely implied the effect of sampling in different years. About 35% of the species were shared among forest types and 41% between sampling years. Using the ACOR scale, abundant and common myxomycetes were represented by species present in the three forest types, with clear changes in abundance across the gradient. However, occasional and rare myxomycete categories showed the loss of several species and the emergence of some others from the dry to the wet ecosystems, demonstrating a turnover of species across the different forest types within the gradient. These changes in species composition may be related to the El Niño Southern Oscillation events. Even though such turnover is a natural phenomenon based on species preferences for certain habitats, it is an important aspect to document, particularly in the less studied tropical regions of the world. In the small area studied herein, data showed that myxomycete dynamics are heavily influenced by the local microclimate. The increased speed and strength of ecological pressures on global biosystems represent a threat to microbial dynamics and perhaps myxomycetes can help offer some clues to understand such unbalances.