Biology subjects

Wesner, J. S.

Publications and source records attributed to Wesner, J. S..

6 recordsLinked to original sources

bioRxiv2024

Size spectra in freshwater streams are consistent across temperature and resource supply

The study explores the individual size distribution (ISD) pattern in ecological communities, characterized by a negative correlation between individual body size and abundance (N [~] M{lambda}). The parameter {lambda} denotes the rate of decline in relative abundance from small to large individuals. Despite known influences of temperature and resource availability on body size, their effects on {lambda} remain diverse. Leveraging data from 2.4 million individual body sizes in continental freshwater streams, the research the hypothesis that {lambda} varies as a function of temperature and resource supply. Surprisingly, despite varied environmental conditions and complete species turnover, minimal variation in {lambda} (mean = -1.2, sd = 0.04) was observed, with no discernible impact from temperature or resource supply. The unexpected {lambda} value of -1.2 suggests a higher-than-expected relative abundance of large individuals, challenging assumptions of metabolic scaling at 0.75 and implying large subsidy inputs to large predators. Simulation and mesocosm experiments support a metabolic scaling coefficient of [~]0.4 for freshwater macroinvertebrates. The findings underscore remarkable consistency of individual size distributions in freshwater streams, likely driven by shallow metabolic scaling and large subsidies to large consumers.

ecology↗

bioRxiv2023

Using passive telemetry and environmental variables to predict Silver Carp (Hypophthalmichthys molitrix) movement cues on the northwestern edge of their invasion front

Silver carp Hypophthalmichthys molitrix, are a highly mobile aquatic invasive species in the United States. The James River, South Dakota, USA, is a tributary of the Missouri River and is considered the northwestern leading edge of their invasion front. Understanding silver carp movement patterns on the cusp of this invasion is key to combatting the northwestward expansion of the species. We used passive telemetry to observe large-scale movement patterns of silver carp in the James River, South Dakota. Fifty silver carp were implanted with acoustic transmitter tags in June 2021, and movement data was recorded over a 1.5-year period. Most individuals exhibited site fidelity and stayed within the James River throughout the duration of the study. We used environmental data (i.e., temperature, dissolved oxygen, daily mean discharge, the change in discharge over 24 h and 48 h) and movement data collected from passive telemetry receivers to understand and predict silver carp movement cues in the James River. Daily mean discharge ("flow") was the most important predictor of silver carp movement in the James River. As flow increased, the probability of movement increased from 59% (95% CrI: 34% to 81%) at 1.5 m3/s to 94% (95% CrI: 80 to 99%) at 100 m3/s. In this study, silver carp exhibited a high propensity for movement within the James River, especially during periods of high flow. To prevent further northwestward expansion of these fish, silver carp movements must continue to be monitored and removal and prevention of further range expansion must be prioritized.

ecology↗

bioRxiv2023

Using eDNA to Elucidate Silver and Bighead Carp Range Expansion in Two Missouri River Tributaries in Eastern South Dakota

ObjectiveThis study used environmental DNA (eDNA) sampling methods to determine the possibility of Bighead Carp Hypophthalmichthys nobilis, and Silver Carp H. molitrix, range expansion above barriers to fish movement in two tributaries of the Missouri River in eastern South Dakota. MethodsWe collected water samples above and below two perceived barriers to fish movement: a natural chain of waterfalls in the Big Sioux River and a spillway at the downstream end of a manmade reservoir in the Vermillion River. We used filtration methods to collect invasive carp eDNA from water samples and implemented qPCR techniques to quantify the amount of eDNA in each sample. A total of 213 samples and 38 field blanks were collected over two years (2021/2022). ResultWe detected carp eDNA below both barriers in both years, and above the barrier in the Vermillion River in 2022. The probability of detecting eDNA below the barrier in the Big Sioux River was 51% (95% Credible Interval (CrI): 2 to 97%) and 77% (95% CrI: 8 to 99%) in the Vermillion River. The probability of detecting eDNA above both barriers was significantly smaller: 1% (95% CrI: 0.02 to 24%) for both rivers. ConclusionThe detection of positive samples above the spillway barrier in the Vermillion River provides the first evidence that Bighead and Silver Carp may have expanded their range to habitats upstream of their documented range in eastern South Dakota. Impact StatementThis study demonstrates the utility of using eDNA sampling methods to detect Bighead and Silver Carp in areas of both known and unknown invasive carp presence in smaller tributary streams to the Missouri River.

ecology↗

bioRxiv2023

Detecting differences in Size Spectra

O_LIThe 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 ({lambda}) of the power law. C_LIO_LIMany methods have been proposed for estimating{lambda} most of which involve binning the data, summing abundance within bins, and then fitting a ordinary least squares (OLS) regression in log-log space. However, recent work has shown that binning procedures may return biased estimates of size spectra exponents compared to procedures that directly estimate{lambda} using maximum likelihood estimation (MLE). Despite this variability in estimates, it is unclear if the relative change across environmental gradients is consistent across methodologies. Here, we used simulation to compare the ability of two binning methods (NAS, ELBn) and MLE to 1) recapture known values of{lambda} , and 2) recapture parameters in a linear regression measuring the change in{lambda} across a hypothetical environmental gradient. We also compared the methods using two previously published body size datasets across a pollution gradient and a temperature gradient C_LIO_LIMaximum likelihood methods always performed better than common binning methods, which demonstrated consistent bias depending on the simulated values of{lambda} . This bias carried over to the regressions, which were more accurate when{lambda} was estimated using MLE compared to the binning procedures. Additionally, the variance in estimates using MLE methods is markedly reduced when compared to binning methods. C_LIO_LIThe uncertainty and variation in estimates when using binning methods is often greater than or equal to the variation previously published in experimental and observational studies, bringing into question the effect size of previously published results. However, while the methods produced different slope estimates from previously published datasets, they were in qualitative agreement on the sign of those slopes (i.e., all negative or all positive). Our results provide further support for the direct estimation of{lambda} using MLE (or similar procedures) over the more common methods of binning. C_LI

ecology↗

bioRxiv2023

Bayesian hierarchical modeling of size spectra

O_LIA 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 body sizes in an ecosystem. C_LIO_LIThe ISD is described by a power law and a major goal of size spectra analyses is to estimate the exponent of the power law, {lambda}. However, while numerous methods have been developed to do this, they have focused almost exclusively on estimating {lambda} from single samples. C_LIO_LIHere, we develop an extension of the truncated Pareto distribution within the probabilistic modeling language Stan. We use it to estimate multiple {lambda}s simultaneously in a hierarchical modeling approach. C_LIO_LIThe most important result is the ability to examine hypotheses related to size spectra, including the assessment of fixed and random effects, within a single Bayesian generalized (non)-linear mixed model. While the example here uses size spectra, the technique can also be generalized to any data that follows a power law distribution. C_LI

ecology↗

bioRxiv2020

Choosing priors in Bayesian ecological models by simulating from the prior predictive distribution

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 response variable. This is particularly true for common models in ecology, like generalized linear mixed models, which may have a link function and dozens of parameters, each of which needs a prior distribution. We suggest that this difficulty can be overcome by simulating from the prior predictive distribution and visualizing the results on the scale of the response variable. In doing so, some common choices for non-informative priors on parameters can easily be seen to produce biologically impossible values of response variables. Such implications of prior choices are difficult to foresee without visualization. We demonstrate a workflow for prior selection using simulation and visualization with two ecological examples (predator-prey body sizes and spider responses to food competition). This approach is not new, but its adoption by ecologists will help to better incorporate prior information in ecological models, thereby maximizing one of the benefits of Bayesian data analysis.

ecology↗