Climate Change and Range Shifts
Isaac Shepard |
One of the observed effects of climate change is the shifting and changing of species geographic ranges. It has often been though that this is primarily a direct response of animals to changing abiotic conditions, such as temperature or precipitation, which can have strong direct effects on the growth and survival of many animals.
However, climate and abiotic variables can have strong indirect effects on animals’ growth and survival as well by modifying species interactions. Though there is a large body of theoretical literature that attempts to explain the relative roles of species interactions and environmental conditions for determining species ranges, there have been very few empirical studies in this field, particularly using animals. |
Using field experiments and analysis of long-term community survey data at the Rocky Mountain Biological Laboratory (RMBL), I am examining the relative importance of both biotic and abiotic factors for controlling species ranges. At RMBL we have recently noticed that several species of caddisflies have been shifting their ranges from montane to subalpine elevation ponds. Using these ‘natural’ transplants, I am conducting field experiments with cages along a gradient of pond permanence at the new upper-elevational limit of these range-shifting taxa.
By looking at predation and competitive interactions in these cages, I can start parsing apart how the growth rate and survival of range shifting taxa are modified by abiotic and biotic forces and the interaction between them. Tools such as stable isotope analysis of diets allow me to quantify how much of observed changes in survival can be attributed to predation.
Range shifts will likely have consequences for ecosystem functioning. As new species move into previously unsuitable habitats, it is highly probable they will disrupt the pre-established network of energy flow through the community.
Using the same system of caddisflies, I am looking at how detritus breakdown rates are altered as community composition changes. By adding known amounts of detritus to the cages previously described, I can begin to quantify how new species will impact nutrient flow in these oligotrophic ponds.
In tandem with a larger, collaborative mesocosm experiment, these results will help us better understand how future food webs might change nutrient dynamics in aquatic habitats.
Using the same system of caddisflies, I am looking at how detritus breakdown rates are altered as community composition changes. By adding known amounts of detritus to the cages previously described, I can begin to quantify how new species will impact nutrient flow in these oligotrophic ponds.
In tandem with a larger, collaborative mesocosm experiment, these results will help us better understand how future food webs might change nutrient dynamics in aquatic habitats.
Species Interactions and Range Shifts
Species interactions can be strongly impacted by the abiotic stage on which they are played out. As global climate continues to change, it is imperative that we understand how these changes to the abiotic environment will alter species interactions and thus community and even ecosystem dynamics. It is projected that, if current climate trends continue, there will be an increase in heat wave events where temperatures rapidly rise well above the optimum for many organisms.
Beyond physiological changes, we might expect predators to change their feeding behaviors in response to these stressful conditions. At UMaine, I am conducting laboratory experiments determine whether there are generalizable patterns in the feeding responses of both invertebrate and fish predators to heat waves.
Beyond physiological changes, we might expect predators to change their feeding behaviors in response to these stressful conditions. At UMaine, I am conducting laboratory experiments determine whether there are generalizable patterns in the feeding responses of both invertebrate and fish predators to heat waves.