Predicting where species occur on a landscape is a fundamental aspect of ecology and an essential step in the conservation of biological diversity. Environmental niche modeling is a common tool for predicting species distributions, but limited understanding of causal relationships between the occurrence or abundance of a species and environmental variables limits the generality of these models. Improved understanding of how individual performance varies along environmental gradients is necessary to develop mechanistically-based environmental niche models. This research is motivated by the observation that the distribution of many stream fishes varies along a stream size gradient, but little is known about the mechanistic relationship between stream size and species distribution. The project will develop niche models to predict distribution of fish species in streams draining the Flint Hills of the central United States, which exhibit a strong temperature gradient from headwaters to large rivers. Given the universal importance of temperature as an environmental factor constraining metabolic, survival, and growth rates of individuals and vital rates of populations, it is predicted that temperature-dependent performance varies among species and determines among-species differences in distributional patterns. This study will test that hypothesis by quantifying inter- and intraspecific variation in egg developmental rate as a function of temperature to see if it explains differences in stream size - abundance relationships among four fish species.
This study will provide mechanistically-based environmental niche models for four temperate freshwater fish species, which will inform conservation planners about current distributions and distributional changes in response to anthropogenic climate change. The project will also advance a broadly-applicable framework for developing environmental niche models for other temperate freshwater fish species, particularly threatened and endangered species. These models will be disseminated to state natural resource agencies and will be incorporated into planning tools used to inform conservation efforts in the Great Plains. This project will provide an undergraduate student with practical research experience in field and laboratory settings and support the dissertation research of a doctoral student.
Predicting where species occur on a landscape is a fundamental goal of ecological research and an essential step in the conservation of Earth’s biodiversity. Environmental niche modeling is a popular tool for predicting species distributions, but limited understanding of causal relationships between the abundance of a species and environmental predictor variables limits the ability of these models to accurately forecast future distributions of species. This research was motivated by the observation that the abundances of many stream fishes vary along a stream size gradient, but little is known about the causal relationship between stream size and species abundance. Stream temperature increases from headwaters to large river mainstems in North America and may directly affect the performance of headwater and river mainstem species, differently. To test this hypothesis, we used laboratory experiments to quantify the effect of temperature on egg hatch success of two headwater species (Fathead minnow and Bluntnose minnow) and one mainstem species (Bullhead minnow). Our results indicated that the tributary species perform better (higher egg hatch success) at lower temperatures and have a narrower range of performance compared to the river mainstem species. Next, we developed a predictive model to forecast stream temperatures at the end of the 21st century for over 7900 stream reaches in central Kansas. We projected egg hatch success of the three species to all streams under present-day and future water temperatures. These projections suggest that elevated stream temperatures at the end of the 21st century will lead to a decline in egg hatch success (and possibly abundance) for the Fathead minnow and bluntnose minnow and an increase for the Bullhead minnow (see map). This project provided process-based environmental niche models for the three study species, which can be applied immediately by natural resource managers in Kansas to inform conservation and management decisions for stream ecosystems. The predictive temperature model is also available to natural resource managers and will be an important tool for forecasting a variety of temperature-dependent ecosystem processes (e.g., growth rates of game fishes, nutrient cycling) in prairie streams and rivers. More generally, we demonstrate the utility of a phylogenetic comparative (comparison of species) approach to developing environmental niche models that can be extended to other temperate stream fishes, particularly threatened and endangered species. This project provided supplies and equipment for an additional dissertation chapter for a doctoral student as well as research experience for two undergraduates at Kansas State University. Undergraduate training opportunities encompassed a variety of skills vital for a career in the environmental sciences and included: stream fish surveying, captive breeding and rearing of fish, data management and statistical analysis, and application of geographic information systems to environmental science. One undergraduate carried out an independent research project and presented findings at the Kansas Natural Resources Conference. To date, research findings have been disseminated at four scientific conferences in the format of four oral presentations and two poster presentations. Two manuscripts are currently in preparation for publication in high-quality ecology journals.
