Brandon Barton Hometown: Twin Falls, Idaho Advisor: Ozwald Schmitz

There is a general consensus within the scientific community that the global climate is changing at an unprecidented rate (Vitousek 1994, Cox et al. 200, IPCC 2001). Evidence suggests that anthropogenic emissions of greenhouse gases altered climate patterns during the twentieth century (Alward et al. 1999, Stott et al. 2001, Johns et al. 2003). As a result, the mean global temperature is predicted to rise 1.4 to 5.8 degrees celcius by the end of the twenty-first century, accompanied by changes in precipitation patterns, storm severity and frequency, and rising sea levels (IPCC 2001). Undoubtedly, these changes will have drastic effects for the geographic distribution of organisms and ecosystems globally (Kareiva et al. 1993, VEMAP members 1995, Wardel et al. 1998, Peteet 2000, Stenseth et al. 2002, Walther et al. 2002, Williams et al. 2002, Parmesan and Yohe 2003, Schmitz et al. 2003).

Less certain, however, is how climate change will affect species interactions within ecological communities (Ives 1995, Davis et al. 1998, Schmitz et al. 2003). Climate is an important component shaping species distributions, interactions and life histories (Kareiva et al. 1993). For an ectothermic animal, its biological rates are intimately linked to the biophysics of its habitat (Brown et al. 2004). Seemingly small changes in temperature and precipitation, such as those predicted by climate change models, can have large effects on individuals (Chase 1996, Pitt 1999, Ovadia and Schmitz 2004). Animals can respond to perturbation rapidly (Walther et al. 2002), but different species within food webs may respond in different ways (Pitt 1999, Pimm 2001, Thomas et al. 2001, Beckerman 2002, Voight et al. 2003, Brown et al. 2004, Jiang and Morin 2004). Because climate change is expected to affect species differentially, it is also expected to result in community destabilization (Davis et al. 1998, Harrington et al. 1999, Walther et al. 2002, Schmitz et al. 2003, Voight et al. 2003). However, until recently, the importance of trophic interactions has largely been ignored in the scientific literature (Lensing and Wise 2006, Biro et al. 2007, Suttle et al. 2007).

My goal in the proposed research is to reduce some of the uncertainty around effects of climate change on community structure and function by examining the effects of changing climate on trophic interactions within New England old-field communities comprised of arthropod preditors and herbivores, and herbaceous plants. I will manipulate within experimental mesocosms the levels of biophysical variables (temperature and precipitation) as forecasted by climate change scenarios specific to the region. Using this approach, I will determine the effects of climate change on these communities, as well as the mechanisms by which these effects arise. In doing so, it is my aim to develop an understanding of how climate change will affect interspecific interactions that can be generalized to other ecological communities.

Exploring the effects of climate change in this system has several advantages. A great deal of research has been previously conducted on arthropod communities here and a working knowledge of the dynamics of this system has been attained (reviewed in Schmitz 2004). Although the system has high species richness, it appears that only a few dominant species are drivers of communiy dynamics, and these dominant interactors have been identified and their interactions well-studied (Beckerman et al. 1997, Schmitz et al. 1997, Schmitz 1998, 2003, 2004, Beckerman 2002, Ovadia and Schmitz 2002, 2004). These are short-lived species that produce measurable effects within a timeframe of a single-season field experiment to no more than three consecutive field seasons (e.g., Schmitz and Suttle 2001, Schmitz 2003). Also, previous research has demonstrated this system is sensitive to small changes in climate, similar to those predicted by global change models (Ovadia and Schmitz 2004). Because the focal-species are small and inhabit relatively small home ranges, I can overcome many of the logistical challenges inherent in studying ecological communities by conducting experiments in small-scale enclosures (Schmitz 2004). The mesocosm approach has strong statistical power by allowing sufficient replication and good control treatments. It is also logistically more feasible to implement climate-altered treatments at small scales than larger. Finally, insights about mechanisms of species interactions from small-scale arthropod studies have previously been shown to accurately scale-up to provide understanding of other systems (e.g., Schmitz 2005).