Abstract
Predicting the effects of climate change on community composition is hampered by the lack of integration between long term data sets tracking the effects of natural climate change and the results of experimental climate manipulations. Here we compare the effects of change in climate through time to experimental warming on the composition of high elevation ant communities at the Rocky Mountain Biological Station in Gothic Colorado. We take advantage of a 20‐year continuously running warming experiment which has increased soil temperature by 1.5°C and advanced snowmelt by 10 days and compare the effects of this experimental warming to natural changes in climate over the past 13 years across three sites spread along a 420‐m elevation gradient representing a roughly 1°C difference in average annual soil temperature and average advanced snowmelt of 2 weeks. We compared ant community data collected at all four sites in 1997 to collections made at the same sites in 2010. From 1997 to 2010 there was a community wide shift in ant composition along the natural climate gradient with ant communities shifting to higher elevations. Ant communities in the experimental warming site also changed, but they shifted orthogonally to those along the gradient. Interestingly, after 20 years of experimental warming, there is little discernible effect on ant communities in experimentally warmed plots compared to control plots. This discrepancy between the climate manipulation and elevation gradient is probably an effect of the spatial scale of the experimental warming. Ants respond to experimental warming in complex ways due to the physical location of their nests and their foraging area. This is a concern for warming experiments, but one that is hard to address for species that cover even modest areas in their foraging.
Highlights
Patterns of species distributions along elevation gradients have a long history of study in ecology due to the relatively rapid change in environmental factors (Rosenzweig 1995)
In 1990, at the mid-elevation, the artificial warming experiment was established at a site roughly 500 m south of the mid-elevation control site to study the effects of climate change on vegetation and the soil mesofauna (Harte et al 1995)
The plots with the most morphospecies were in the experimental warming site and the low elevation site, while the plot with the fewest morpho-species was found in the mid elevation control site
Summary
Patterns of species distributions along elevation gradients have a long history of study in ecology due to the relatively rapid change in environmental factors (Rosenzweig 1995). Studies in community composition along elevation gradients are making a resurgence in part because global temperatures are increasing at an alarming rate, with an increase ranging from 2–78C predicted over this century (IPCC 2007). Studying responses of communities along an elevation gradient provides several benefits, including the ability to document differences along a natural climate gradient and see shifts in species responses at both the lower and upper range limit of a community (Wilson et al 2005, Kelly and Goulden 2008, Warren and Chick 2013). Due to the difficulties in predicting shifts in non-analog climates combined with variable responses of species in the same communities, there has been an increasing focus on documenting empirical range shifts (Parmesan and Yohe 2003, Doak and Morris 2010). The dynamics of such observed shifts are best understood in combination with experiments artificially manipulating climate (Walker et al 2006, Leuzinger et al 2011)
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