Current Post Docs and Graduate Students

James Whitney, MS student (jwhit@ksu.edu). Productivity as a mediator of interactions between native and non-native fish species in an arid-land stream: Does higher production promote species coexistence

The objectives of the proposed research are: 1) to measure primary and secondary productivity along the longitudinal gradient of the Upper Gila River system; 2) to examine the relationship between differing levels of resource quantity and coexistence of native and nonnative fishes; 3) to see how production is allocated between native and non-native species. Measurements of primary and secondary production will be followed by mechanistic experiments quantifying the impacts of non-native species on native species.

Erika Martin, PhD student (erikam86@k-state.edu). Community dynamics of prairie stream fishes.

Josh Perkin, PhD student (JPerkin@k-state.edu). Fragmentation in Great Plains stream networks

Former Students and Post docs

David Hoeinghaus, Post doc 2007 – 2009 (Life-history traits predict conservation status of fishes in Great Plains)

The ability to predict likely extirpations or successful invasions in response to environmental change would greatly facilitate conservation of native species and prevention of species invasions. David developed a comprehensive database of quantitative life-history traits and ecological classifications for fish species in multiple Great Plains watersheds from 1885 to present. He compare traits and ecological classifications of native, extinction-prone and invasive species and develop predictive models of extinction-prone and invasive species for two hydrologically altered river basins. Quantitative life-history traits distinguished two sets of extinction-prone species (opportunistic and periodic species) nested within the broader gradient of life-history strategies of native species in Great Plains basins. Trait similarities of extinction-prone and currently stable native species may indicate species warranting proactive conservation. Primarily equilibrium-adapted invasive species associated with stabilized flows were distinguished from native species adapted to naturally dynamic flows. Within the river network, life-history traits were tied to habitat associations for both extinction-prone and invasive species, and invasive congeners of native species appear to exhibit environmental matching to less impacted habitats. Native species that specialize on a single habitat type were more often extinction-prone than species occurring in multiple habitat types. Classification trees successfully predicted extinction-prone and invasive species similarly in both basins based on linear and non-linear combinations of life-history traits. Traits of extinction-prone and invasive species in our Great Plains basins, as well as across three different river ecosystem types also with altered hydrology, strongly correspond with life-history theory considering the natural hydrologic conditions of each basin and shared anthropogenic impact. When habitat alteration drives species extirpations and facilitates invasions, knowledge of the natural conditions to which native species are adapted and the type of environmental change can provide the template for predicting traits of species at risk of extirpation or likely to invade based on life-history theory.

Tyler Pilger, MS 2009 (Trophic relations in the upper Gila River, New Mexico)

Diet and stable isotopes of native and nonnative fishes were used to identify trophic relationships and evaluate potential interactions among native and nonnative fishes in the upper Gila River basin during June-July, 2007 and 2008. These data indicated aquatic invertebrates were a common food for both native and nonnative fishes and that both were highly omnivorous. Native large-bodied fishes were mainly algivore/detritivores and native small-bodied fishes were primarily insectivores. Small-bodied nonnative fishes fed on detritus and aquatic invertebrates. Nonnative predators preyed on small-bodied fishes and predaceous aquatic invertebrates and had significantly higher trophic positions than small and large-bodied native fishes. Although nonnative predators did not rely exclusively on native fishes as prey, their presence extended community food-chain lengths. The combined predation on juvenile native fishes by multiple apex predators might threaten persistence of native fishes. However, the high degree of omnivory suggested that impacts of nonnative predators may be more subtle and dependent on environmental variability.

Michelle Evans-White, Post doc 2006-2007 (Forecasting ecological change in aquatic systems in the Great Plains)

This project addressed one of the grand challenges of the 21^st century—evaluating, modeling and forecasting the biological and ecological consequences of accelerating global changes. These global change phenomena are critical for grasslands, an ecosystem of worldwide importance that provides resources and services to human societies worldwide, and an area of particular significance to the Kansas and regional economy. Ecological forecasting must consider changes in land use patterns and disturbance regimes, climate, biota (invasions/removals), and hydrological and biogeochemical cycles. A better understanding and ability to forecast these phenomena and their consequences are fundamental to sustaining grassland ecosystem services: supplying clean water, recycling essential nutrients, sequestering carbon, preserving biodiversity, and guarding against invasive species and emerging diseases.

Deb Walks (Understanding Ecological Thresholds in Aquatic Systems through Retrospective Analysis)

We will document how a dramatic shift in the hydrologic state of Great Plains rivers and streams has produced a biotic state change in this system. This hydrologic change results from human alteration of surface water flow through agricultural diversion, groundwater pumping, construction of small impoundments, and changing cultivation techniques. We hypothesize that these hydrologic changes have fundamentally altered system connectivity, leading to observed declines in key species. We have observed two major state changes (thresholds) in our region of the Great Plains, 1) drying of major river channels and 2) extirpation of fish and invertebrate species. Fragmentation of these river networks is postulated to have affected the distribution of fishes throughout the Great Plains, leading to extirpation of native species from some rivers and the introduction and spread of exotic species in others, resulting in a strong shift in community composition that may compromise the biotic integrity and ecosystem function of these lotic ecosystems.

Katie Bertrand, PhD 2007 (Interactive effects of disturbance regime and species composition on ecosystem function of prairie streams)

Climate changes associated with anthropogenic activities will likely effect the hydrologic cycle in the Great Plains by increasing the intensity, but reducing the frequency of flood events.  Thus, individual flood events may become more severe and droughts will be prolonged.  The primary focus of this research is test the effects of these climate change scenarios on stream ecosystem function.  In particular, we are interested in testing the interactive effects of disturbances (i.e., floods and drought) and fish species composition on stream metabolism and nutrient retention.  Working primarily on the Konza Prairie Biological Station (KPBS), we are using experimental streams to manipulate fish species composition, flood frequency and drought duration.  We also are monitoring the effects of flooding and drought in Kings Creek, a natural prairie stream located on KPBS.

Darren Thornbrugh, MS 2008 (Fish assemblage structure in adventitious streams)

The interface zones between large rivers and tributary streams may play an important role in structuring fish assemblages. By studying these systems from a landscape perspective (e.g., riverscapes), the properties of stream networks that influence fish assemblage structure may be revealed. The objective of this study was to test the association of fish community structure and habitat in adventitious streams. We predicted an abrupt change in community structure between adventitious streams and the Kansas River that coincides with changes in physical habitat. Our analysis is being conducted at two scales, a basin wide stream survey and more intensive collections in three adventitious streams in the Kansas River basin.

Nate Franssen, MS 2007 (Trophic relations of the Colorado pikeminnow (Ptychocheilus lucius) in the San Juan River, New Mexico and Utah)

The Colorado pikeminnow (Ptychocheilus lucius) was historically the top predator in the San Juan River, New Mexico.  However, Colorado pikeminnow and other native fishes have undergone a drastic declines in abundance with the construction of impoundments and the introduction of nonnative fishes.  Whereas native fishes were the main forage of the Colorado pikeminnow, the current prey assemblage includes many small-bodied nonnatives.  Our current investigation is evaluating the adequacy of the prey base in the San Juan River to support the Colorado pikeminnow.  With the use of the stable isotopes, 15N and 13C, a food web will be constructed which will help identify key trophic interactions.  Field and mesocosm experiments will be conducted to quantify predator-prey interactions and assess the susceptibility of the native versus abundant nonnative fishes as prey for the Colorado pikeminnow.

Tim Strakosh, PhD 2006 (The effects of water willow establishment on littoral community composition: with focus on age-0 centrarchids in Kansas reservoirs)

Sportfish production in many Kansas reservoirs has declined in recent years, likely associated with a reduction in littoral structure associated with reservoir aging.  One strategy to mitigate for such a decline is through habitat enhancement.  In Kansas water willow (Justicia americana) has been planted in reservoirs to provide littoral nursery habitat for age-0 largemouth bass (Micropterus salmoides) and Lepomis spp.  However, the effects of water willow establishment on littoral communities, including age-0 largemouth bass and Lepomis spp., are unknown.  The goals of this four year study are to 1) investigate the contribution of water willow establishment on age-0 largemouth bass and Lepomis spp. density, growth, diet, and condition relative to other environmental factors in three large impoundments, 2) investigate what effects water willow may have on littoral fish and invertebrate communities in these impoundments, and 3) compare age-0 largemouth bass and Lepomis spp. density, growth, diet, and condition from the large impoundments to stable, well vegetated small impoundments with abundant centrarchid populations.  A smaller component of this study is to test the inundation and desiccation tolerance of water willow by simulating water level fluctuations that may be experienced in the large reservoirs.

Layne Knight, MS 2004 (Effects of largemouth bass predation on native stream minnows: implications for conservation of the endangered Topeka shiner)

Largemouth bass have been widely introduced in Kansas and have been implicated in the decline of the federally endangered Topeka shiner (Notropis topeka).  Several correlative studies have contributed losses of native minnows, subsequent to the damming of small streams, to predation by introduced predators.  However, no direct evidence is available to show that predation is the mechanism responsible for the extirpation of Topeka shiner populations in these situations.  The goal of this research is to assess the relative susceptibility of Topeka shiners and other native minnows to predation by largemouth bass by evaluating the behavioral responses of a guild of minnows, including Topeka shiners to a threat of predation by largemouth bass.  In addition, research is conducted in experimental streams where bass are allowed to forage on an assemblage of minnows (Topeka shiners, red shiners, common shiners, bluntnose minnows) to evaluate the actual susceptibility of the various species.  A final facet of this research is to investigate the functional response of largemouth bass to prey densities and how this will influence the population dynamics of prey species.

Jeff Falke, MS 2004 (Upstream effects of large reservoirs on native stream fishes)

Due to their prominence on the landscape, large reservoirs can potentially affect native fish assemblages by isolating fishes in tributary streams and by serving as a source for non-native competitors.  Using a GIS/landscape approach, we are investigating 1) how distance from a reservoir influences native fish assemblages in streams within a reservoirs watershed, 2) whether abundance of introduced reservoir species varies with distance from a reservoir, and 3) if connectivity to a reservoir can influence native fish assemblages.  Field experiments comparing fish assemblages in reservoir influenced streams (connected tributaries) with nearby control streams will be used to quantify the influence of reservoir connectivity on fish assemblage structure.  On a smaller scale (i.e. that of a single tributary stream) we are exploring longitudinal gradients in fish assemblage structure to evaluate if species occurrences are driven more by habitat characteristics or by proximity to reservoirs.