ABSTRACT

Freshwater ecosystems support a disproportionate percentage of Earth's biodiversity and are among the most threatened by human activities and global climate change. Insects dominate fresh-water ecosystems in terms of animal biodiversity and ecological processes. Temperature controls insect growth, developmental timing, survival, and reproduction, which influence both the distributions of individual species and the specific set of species that occur in different freshwater ecosystems. Thus, many effects of global change and other anthropogenic activities on freshwater ecosystems will likely be manifested through their thermal effects on aquatic insects. The thermal limits of individual freshwater insect taxa and the underlying physiological mechanisms that determine those limits still remain poorly understood. This research has practical importance because resource agencies use aquatic insects and other invertebrates to make inferences about ecological health and water quality. However, these data are often difficult to interpret, because we have a poor understanding of how and why species are differentially responsive to elevated temperatures. This collaborative project links researchers with a broad range of expertise to understand how temperature affects organismal physiology, life-history outcomes, and ultimately the distribution of species across entire landscapes.

The research team will experimentally manipulate thermal regimes to quantify the effects of temperature on life-history outcomes (survival, growth rates, development times, size and fecundity) of a diversity of mayfly (Ephemeroptera) species. Laboratory experiments will identify how the specific physiological processes that affect life-history outcomes (respiration, energy allocation, the production of metabolites, and gene expression) respond to different temperatures. These laboratory studies will be used to refine ecological niche models (empirically derived relationships between environmental temperatures and species distributions in time and space) that are used in freshwater biodiversity assessment and monitoring. In particular, these studies will clarify which descriptors of environmental temperatures (e.g. mean annual temperature, mean summer temperature, the magnitude of diel thermal change, etc.) are most important to species performance. Ultimately, these studies are intended to provide a robust understanding of the linkages between thermal physiology, life-history variation, and species distributions. Robust outreach efforts will make this understanding useful to the large ecological monitoring community.

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