![]() This idea was further supported by the experimental results. The dietary shift was consistent with what a shift toward cannibalism would look like, suggesting that where spiders were larger-and reproductive rates higher-spiders cannibalized each other more often. These creatures are becoming larger and producing more offspring, which is creating more competition for resources. Using stable isotope analysis, Koltz then found that the spiders at the site with larger females had different diets than at the site with smaller females. However, the results were surprising due to the fact that one would assume larger spiders meant there would be more offspring because they produce more young. While analyzing the arachnoids in the field study, Koltz determined that the presence of larger female spiders meant there were fewer juvenile spiders. This allowed them to see how a wolf spider's diet is affected when living in higher spider densities. 'Space and resources on the tundra are finite,' Koltz said.ĭuring the study, Koltz and her team compared their observations in Alaska with a separate experiment that manipulated the number of wolf spiders in an enclosed area. Louis while working at two sites in the Alaskan ArcticĪnd previous studies have found wolf spiders have been greatly affected in the Arctic as the summer season grows longer due to climate change.Īlong with increasing their body size, females will also produce more offspring in warmer weather.īut whether this change actually results in more spiders in the wild remains an important question. Given the widespread distribution of wolf spiders in arctic ecosystems, body size shifts in these predators as a result of climate change could have implications for lower trophic levels and for ecosystem functioning.The behavior was observed by researchers from Washington University in St. ![]() Our results suggest that body size variation in wolf spiders is associated with variation in intraspecific competition, feeding ecology and population structure. We observed no changes in wolf spider feeding ecology in association with short-term experimental warming. Higher rates of density-dependent cannibalism are further supported by the results from our mesocosm experiment, in which individuals occupied higher trophic positions in plots with higher wolf spider densities. lapponica, the unexpected finding of fewer juveniles with larger females suggests an increase in density-dependent cannibalism as a result of increased intraspecific competition for resources. Because female body size is positively related to fecundity in P. We found that juvenile abundance is negatively associated with female size and that wolf spiders occupied higher trophic positions where adult females were larger. Additionally, we performed a mesocosm experiment to investigate how variation in wolf spider density, which is likely to change as a function of body size, influences feeding ecology and its sensitivity to warming. We investigated the population structure and feeding ecology of the dominant wolf spider species Pardosa lapponica at two tundra sites where adult spiders naturally differ in mean body size. Whether these changes are affecting their populations and role within food webs is currently unclear. In particular, wolf spiders, one of the most abundant arctic invertebrate predators, are becoming larger and therefore more fecund. Body size changes have been documented in several species in the Arctic, a region that is warming rapidly. adult to juvenile ratio) and the strength of intraspecific competition. Increasing body size can consequently trigger changes in population density, population structure (e.g. For example, among invertebrates, there is typically a positive correlation between female body size and reproductive output. Changes in this key functional trait can therefore have important implications for populations as well. Body size influences an individual's physiology and the nature of its intra- and interspecific interactions.
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