Climate change is altering the ecological scenario of many species as a result of frequent and prolonged drought events. During the past decade, the effects of climate change on species distribution and persistence probabilities have been widely studied (mainly based on simulations), but its effects on ecological interactions remain little understood. However, its potential effects on ecological interactions, and particularly on pollination and seed dispersal interactions (which play a key role in plant reproduction) may be compromising community structure in the long-term. To gain insight into this issue we used a highly-specialized tripartite mutualistic system with a keystone mistletoe (Tristerix corymbosus), its pollinator (the hummingbird Sephanoides sephaniodes) and its disperser (the arboreal marsupial Dromiciops gliroides). We studied flower and fruit production, along with visitation rates of the mutualist animals during an average (2012) and a dry (2015) austral summer seasons. We assessed visitation rates of the pollinator and the seed disperser using camera traps, and we calculated annual mistletoe mortality based on plant censuses.
Results/Conclusions
Drought in our study area affected precipitation (358 mm in 2012 versus 15 mm in 2015) and soil water availability (0.30 m3/m3of water volumetric content in 2012 versus 0.15 m3/m3in 2015), being the driest summer recorded since 1950. Although pollinator visitation rates were not significantly different between average and dry summer seasons, during the dry summer flower and fruit production experienced a significant reduction, as well as seed disperser visitation rates. Likewise, T. corymbosusannual mortality increased from 12% in 2012 to 23% in 2015 as result of host plant drying. These results suggest that climate change may have cascade effects on ecological interactions, indirectly affecting key processes at the community level in the Valdivian temperate rainforest, as consequence of water shortage stress. Severe drought events result in prolonged water shortage, decreasing flower and fruit production, and therefore impacting on pollination and seed dispersal rates. Long-term research is essential to provide the knowledge necessary to understand how key ecological processes may be affected in a warming world.