Jeff Wesner

University of South Dakota | USD · Department of Biology

The distribution of body size in communities is remarkably consistent across habitats and taxa and can be represented by size spectra, which are described by a power law. The focus of size spectra analysis is to estimate the exponent ( λ ) of the power law. Many methods have been proposed for estimating λ most of which involve binning the data, sum...

A fundamental pattern in ecology is that smaller organisms are more abundant than larger organisms. This pattern is known as the individual size distribution (ISD), which is the frequency of all individual sizes in an ecosystem, regardless of taxon. The ISD is described by power law distribution with the form f(x)=Cx λ , and a major goal of size sp...

Background One of the most important considerations for acoustic telemetry study designs is detection probability between the transmitter and the receiver. Variation in environmental (i.e., wind and flow) and abiotic (i.e., bathymetry) conditions among aquatic systems can lead to differences in detection probability temporally or between systems. I...

Despite their diversity, global distribution, and apparent effects on host biology, the rules of life that govern variation in microbiomes among host species remain unclear, particularly in freshwater organisms. In this study, we sought to assess whether geographic location, taxonomy (order, family, and genus), or functional feeding group (FFG) des...

Background One of the most important considerations for acoustic telemetry study designs is detection probability between the transmitter and the receiver. Variation in river conditions and flow regimes among river systems can lead to differences in detection probability between systems. In this study we evaluate the detection probabilities of two...

Climate change projections in the western United States suggest that snowpack levels and winter precipitation will decline, but mean annual precipitation levels will remain unchanged. Mountain streams that once saw a constant source of water from snowpack will begin to see large seasonal variation in flow. Increased stream intermittency will create...

Aquatic insects undergo substantial shifts in their ecology during development, such as changing from a benthic consumer stage (e.g., larva) to a pelagic non-consumer stage (e.g., non-feeding pupae). Fish may differentially target these life-stages during predation, but the prevalence of this feeding is largely unknown. To determine how stage-speci...

Abstract Many aquatic invertebrates are declining or facing extinction from stressors that compromise physiology, resource consumption, reproduction, and phenology. However, the influence of these common stressors specifically on consumer–resource interactions for aquatic invertebrate consumers is only beginning to be understood. We conducted a fie...

Blue Sucker Cycleptus elongatus is a species of concern across much of its native range due to population fragmentation and habitat loss. A key component of managing this species is monitoring various population characteristics including size structure. A common way to quickly index population size structure is to calculate the proportional size di...

Bayesian data analysis is increasingly used in ecology, but prior specification remains focused on choosing non‐informative priors (e.g., flat or vague priors). One barrier to choosing more informative priors is that priors must be specified on model parameters (e.g., intercepts, slopes, and sigmas), but prior knowledge often exists on the level of...

Accepted version of this manuscript can be found here: https://doi.org/10.1111/gcb.15862 The distribution of abundance and biomass within ecological communities is related to trophic transfer efficiency from prey to predators. While it is considered to be one of the few consistent patterns in ecology, spatiotemporal variation of this relationship a...

Parameters describing the negative relationship between abundance and body size within ecological communities provide a summary of many important biological processes. While it is considered to be one of the few consistent patterns in ecology, spatiotemporal variation of this relationship across continental scale temperature gradients is unknown. U...

Individuals may delay dispersing from their natal habitat, even after maturation to adulthood. Such delays can have broad consequences from determining population structure to allowing an individual to gain indirect fitness by helping parents rear future offspring. Dispersal in species that use delayed dispersal is largely thought to be opportunist...

Anticipating the number of hospital beds needed for patients with COVID-19 remains a challenge. Early efforts to predict hospital bed needs focused on deriving predictions from SIR models, largely at the level of countries, provinces, or states. In the USA, these models rely on data reported by state health agencies. However, predicting disease and...

Bayesian data analysis is increasingly used in ecology, but prior specification remains focused on choosing non-informative priors (e.g., flat or vague priors). One barrier to choosing more informative priors is that priors must be specified on model parameters (e.g., intercepts, slopes, sigmas), but prior knowledge often exists on the level of the...

In this chapter, we synthesize the state of the science regarding ecological subsidies and contaminants at the land-water interface and suggest research and management approaches for linked freshwater-terrestrial ecosystems. Specifically, we focus on movements of animals with complex life histories and the detrital inputs associated with animal and...

Animals with complex life histories such as aquatic insects and amphibians link freshwater and terrestrial ecosystems when they transition from water to land during development. This transition requires metamorphosis from juvenile to adult life stages. Metamorphosis is a stressful and ecologically sensitive life history event. Exposure to contamina...

Anticipating the number of hospital beds needed for patients with COVID-19 remains a challenge. Early efforts to predict hospital bed needs focused on deriving predictions from SIR models, largely at the level of countries, provinces, or states. In the United States, these models rely on data reported by state health agencies. However, predictive d...

Understanding what makes food webs stable has long been a goal of ecologists. Topological structure and the distribution and magnitude of interaction strengths in food webs have been shown to confer important stabilizing properties. However, our understanding of how variable species interactions affect food‐web structure and stability is still in i...

The floodplains of large rivers have been heavily modified due to riparian development and channel modifications, both of which can eliminate shallow off-channel habitats. The importance of these habitats for aquatic organisms like fishes is well studied. However, loss of off-channel habitat also eliminates habitats for the production of emerging a...

The Prairie Pothole Region (PPR) of the United States and Canada is a vast network of wetlands that provide rich habitat for waterfowl and aquatic organisms. Much of the landscape surrounding these wetlands is dominated by agriculture, allowing for contaminants such as neonicotinoid insecticides and selenium to enter these water bodies following pr...

Bacterial endosymbionts, particularly Wolbachia (Rickettsiales: Rickettsiaceae), Rickettsia (Rickettsiales: Rickettsiaceae), and Cardinium (Bacteroidales: Bacteroidaceae), are commonly found in several arthropod groups, including insects. Most estimates of the global infection rate of Wolbachia (52% [95% credible intervals: 44-60]) show that these...

Aquatic insects link aquatic and terrestrial ecosystems through their metamorphosis and subsequent transition from water to land. Chemical stressors in freshwater, such as agricultural contaminants, can potentially disrupt insect life cycles and reduce the number of insects emerging as terrestrial adults, thereby damaging or severing this linkage....

Diversity and biomass of aquatic insects decline in metal-rich aquatic environments, but the mechanisms by which insects from such environments cope with potentially toxic metal concentrations to survive through adulthood are less well understood. In this study, we measured Zn concentrations and isotopes in laboratory-reared diatoms and mayflies (N...

Predation is a dominant structuring force in ecosystems, but its effects are almost always measured in the ecosystem of the predator. However, the effects of predators can potentially extend across ecosystem boundaries during ontogenetic niche shifts in prey. We compared the effects of fish predation on benthic versus emerging aquatic insects, and...

Wolbachia is a genus of intracellular bacteria typically found within the reproductive systems of insects that manipulates those systems of their hosts. While current estimates of Wolbachia incidence suggest that it infects approximately half of all arthropod species, these estimates are based almost entirely on terrestrial insects. No systematic s...

Insect metamorphosis often results in substantial chemical changes that can alter contaminant concentrations and fractionate isotopes. We exposed larval mayflies (Baetis tricaudatus) and their food (periphyton) to an aqueous zinc gradient (3-340 µg Zn/l) and measured zinc concentrations at different stages of metamorphosis: larval, subimago, and im...

June sucker, Chasmistes liorus , is an endangered lake sucker endemic to Utah Lake, Utah, USA. Over the last two decades, captive-raised June suckers have been stocked into Utah Lake to augment the wild population. However, it has become apparent that the fish stocked from captive stock may not always represent the typical June sucker morphology. T...

Fish are often the top-consumers in freshwater ecosystems, and can strongly affect the biomass of benthic and emerging insects. However, based on our dataset, the study of fish effects is largely limited to experiments that manipulate 1-2 species of cyprinids or salmonids, most of which are water-column foragers. As a result, our knowledge of the r...

Predator-prey interactions are often studied entirely within the ecosystem of the predator. However, many prey transition between ecosystems during development, expanding the effects of predators across ecosystems. Prey are often vulnerable to predation during this transition, facing a predator gauntlet as they leave their source ecosystem. As a re...

Here we synthesize empirical research using meta-analysis to compare how consumer and resource fluxes affect recipient food webs. We tested the following hypotheses: H1) The direct effects of resource fluxes (bottom-up) should be stronger than the direct effects of consumer fluxes (top-down), because resource fluxes are permanent (do not return to...

Aquatic organisms use a variety of biogeochemical reactions to regulate essential and non-essential trace metals. Many of these mechanisms can lead to isotopic fractionation, thus measurement of metal isotopes may yield insights into the processes by which organisms respond to metal exposure. We illustrate these concepts with two case studies, one...

Here we synthesize empirical research using meta-analysis to compare how consumer and resource fluxes affect recipient food webs. We tested the following hypotheses: (H-1) The direct effects of resource fluxes (bottom-up) should be stronger than the direct effects of consumer fluxes (top-down), because resource fluxes are permanent (do not return t...

Review of masters thesis project

Predator community composition can alter habitat quality for prey by changing the strength and direction of consumptive effects. Whether predator community composition also alters prey density via nonconsumptive effects during habitat selection is not well known, but is important for understanding how changes to predator communities will alter prey...

Insects are integral to most freshwater and terrestrial food webs, but due to their accumulation of environmental pollutants they are also contaminant vectors that threaten reproduction, development and survival of consumers. Metamorphosis from larvae to adult can cause large chemical changes in insects, altering contaminant concentrations and frac...

The response of larval aquatic insects to stressors such as metals is used to assess the ecological condition of streams worldwide. However, nearly all larval insects metamorphose from aquatic larvae to winged adults, and recent surveys indicate that adults may be a more sensitive indicator of stream metal toxicity than larvae. One hypothesis to ex...

Variation in trophic position can be caused by structural changes in food webs that may affect the presence of, or be affected by the presence of, individual species. We examined variation in the trophic position of fishes across 14 stream sites in the Bear River drainage, WY, USA. This drainage is the focus of ongoing conservation of northern leat...

Stream metal pollution is a global phenomenon that negatively affects aquatic insect communities. Because most aquatic insects undergo metamorphosis to become winged terrestrial adults, stream metal pollution may also have effects that extend beyond the aquatic habitat boundary. This could occur if, for example, stream metals reduce emerging insect...

Predation effects in streams can cascade to terrestrial food webs through the flux of organisms that develop in the stream and emerge as adults to the terrestrial system. This emergence subsidizes some terrestrial predators, an effect that generally varies based on the magnitude of the subsidy. Factors regulating this magnitude are relatively well...

1. Empirical and theoretical research over the past decade has demonstrated the widespread importance of aquatic subsidies to terrestrial food webs. In particular, adult aquatic insects that emerge from streams and lakes are prey for terrestrial predators. While variation in the magnitude of this subsidy is clearly important, the potential top-down...

Background / Purpose: Ecological models fit two basic purposes: prediction and explanation. But statistical (empirical) models of nature typically incorporate multivariate terms. We explore dimensionality reduction methods that support one or both model purposes. Main conclusion: Partial least squares regression (PLSR) incorporates dimensional...

Rivers and streams are among the most threatened ecosystems worldwide, and their fish assemblages have been modified by anthropogenic habitat alteration and introductions of non-native species. Consequently, two frequently observed patterns of assemblage change over time are species loss and biotic homogenization. In the present study, we compared...

Models of habitat selection often assume that organisms choose habitats based on their intrinsic quality, regardless of the position of these habitats relative to low-quality habitats in the landscape. We created a habitat matrix in which high-quality (predator-free) aquatic habitat patches were positioned adjacent to (predator-associated) or isola...

It is often assumed that indicator species can act as surrogates for conservation of other taxa because the habitat characteristics that limit the distribution of indicators should also affect multiple co-occurring native species. However, this assumption is rarely explicitly tested. Here, we test whether four fish species are potential indicators...

Predation can drive morphological divergence in prey populations, although examples of divergent selection are typically limited to nonreproductive individuals. In livebearing females, shape often changes drastically during pregnancy, reducing speed and mobility and enhancing susceptibility to predation. In the present study, we document morphologi...

I assessed the short-term impact of two sequential scouring floods on the fish assemblage of a small prairie stream. I tested for changes in fish abundance, fish assemblage composition, and fish-habitat associations within individual pools and across a suite of pools following each flood. Before the second flood, 30–90% of fish were removed by sein...

Food webs in different ecosystems are often connected through spatial resource subsidies. As a result, biodiversity effects in one ecosystem may cascade to adjacent ecosystems. I tested the hypothesis that aquatic predator diversity effects cascade to terrestrial food webs by altering a prey subsidy (biomass and trophic structure of emerging aquati...

The native range of brook trout Salvelinus fontinalis in southern Appalachia has been drastically reduced by human activities over the last century. Restoration of brook trout populations was attempted through stocking of hatchery-reared fish that were derived from populations native to northern Appalachia; these northern brook trout are geneticall...

Organisms with complex life histories (CLH) often cross habitat or ecosystem boundaries as they develop from larvae to adults, coupling energy flow between ecosystems as both prey (bottom-up) and consumers (top-down). Predation effects on one stage of this life cycle can therefore cascade across ecosystems, magnifying the impact of local predation....

Research over the past decade has established spatial resource subsidies as important determinants of food web dynamics. However, most empirical studies have considered the role of subsidies only in terms of magnitude, ignoring an important property of subsidies that may affect their impact in recipient food webs: the trophic structure of the subsi...