Abstract
Climate change affects communities both directly and indirectly via changes in interspecific interactions. One such interaction that may be altered under climate change is the ant-plant seed dispersal mutualism common in deciduous forests of eastern North America. As climatic warming alters the abundance and activity levels of ants, the potential exists for shifts in rates of ant-mediated seed dispersal. We used an experimental temperature manipulation at two sites in the eastern US (Harvard Forest in Massachusetts and Duke Forest in North Carolina) to examine the potential impacts of climatic warming on overall rates of seed dispersal (using Asarum canadense seeds) as well as species-specific rates of seed dispersal at the Duke Forest site. We also examined the relationship between ant critical thermal maxima (CTmax) and the mean seed removal temperature for each ant species. We found that seed removal rates did not change as a result of experimental warming at either study site, nor were there any changes in species-specific rates of seed dispersal. There was, however, a positive relationship between CTmax and mean seed removal temperature, whereby species with higher CTmax removed more seeds at hotter temperatures. The temperature at which seeds were removed was influenced by experimental warming as well as diurnal and day-to-day fluctuations in temperature. Taken together, our results suggest that while temperature may play a role in regulating seed removal by ants, ant plant seed-dispersal mutualisms may be more robust to climate change than currently assumed.
Highlights
Understanding how organisms will respond to ongoing changes in climate, leading to subsequent changes in key ecological processes, is essential in order to predict the structure and function of ecosystems in the future (Andrew et al, 2013)
Prediction 1: Rates of seed removal by ants would decrease as a result of experimental warming at the southern site where species, including A. rudis, are closer to their critical thermal maxima (CTmax) (Deutsch et al, 2008; Diamond et al, 2012a; Diamond et al, 2012b; Huey et al, 2012), a pattern previously documented in this study system (Diamond et al, 2012a)
The lack of response to experimental warming contrasts with the prediction that, based on the thermal limits of A. rudis and its disproportionate role in seed dispersal, seed dispersal rate should decline with increasing temperatures
Summary
Understanding how organisms will respond to ongoing changes in climate, leading to subsequent changes in key ecological processes, is essential in order to predict the structure and function of ecosystems in the future (Andrew et al, 2013). To examine the potential for climate change to alter myrmecochory, we experimentally manipulated temperature at two sites in the eastern United States (Duke Forest in North Carolina and Harvard Forest in Massachusetts) and examined overall rates of seed removal as a function of temperature.
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