Abstract Human disturbance increases the invasi-bility of lotic ecosystems and the likelihood of ... more Abstract Human disturbance increases the invasi-bility of lotic ecosystems and the likelihood of hybridization between invasive and native species. We investigated whether disturbance contributed to the invasion of red shiner (Cyprinella lutrensis) and their hybridization with native ...
Abstract Within the upper Ohio River watershed, 3 Etheostoma darter species in the subgenus Notho... more Abstract Within the upper Ohio River watershed, 3 Etheostoma darter species in the subgenus Nothonotus have been documented in disjunct populations and were listed as threatened or endangered in Ohio and Pennsylvania. Tailwater habitat below navigation lock and dam (L/D) installations has been shown to contain diverse darter assemblages. Etheostoma camurum (Bluebreast Darter), E. maculatum (Spotted Darter), and E. tippecanoe (Tippecanoe Darter) often live in similar habitats; thus, we hypothesized that all 3 were occupying tailwater habitat below navigational L/Ds. Electrified benthic trawling verified Bluebreast Darter and Tippecanoe Darter below 8 L/D installations and at water depths varying from 1.4 m to 4.5 m and 1.4 m to 5.9 m, respectively. Spotted Darter was only found below 1 L/D. In the Ohio River, benthic trawling documented Bluebreast Darter and Tippecanoe Darter utilizing habitat located within deposition zones and areas above and below islands. Analysis of contemporary and historic distribution data shows that Bluebreast Darter and Tippecanoe Darter now span large sections of the river, but the range of Spotted Darter is more limited and warrants close monitoring. Our study confirms the effectiveness of utilizing benthic trawling in non-wadeable rivers to survey for benthic species such as river-inhabiting darters.
... subgenus Ulocentra, and 11 members of the proposed sister subgenus Etheostoma were investigat... more ... subgenus Ulocentra, and 11 members of the proposed sister subgenus Etheostoma were investigated with 1033 base pairs of mitochondrial DNA sequence data and 54 osteological characters ... Phylogeography was used to interpret the genetic variation between populations ...
Synopsis The introduction of laboratory methods to animal dietary studies has allowed researchers... more Synopsis The introduction of laboratory methods to animal dietary studies has allowed researchers to obtain results with accuracy and precision, not possible with observational techniques. For example, DNA barcoding, or the identification of prey with taxon-specific DNA sequences, allows researchers to classify digested prey tissues to the species-level, while stable isotope analysis paired with Bayesian mixing models can quantify dietary contributions by comparing a consumer's isotopic values to those derived from their prey. However, DNA-based methods are currently only able to classify, but not quantify, the taxa present in a diet sample, while stable isotope analysis can only quantify dietary taxa that are identified a priori as prey isotopic values are a result of life history traits, not phylogenetic relatedness. Recently, researchers have begun to couple these techniques in dietary studies to capitalize on the reciprocal benefits and drawbacks offered by each approach, with some even integrating DNA-based results directly into Bayesian mixing models as informative priors. As the informative priors used in these models must represent known dietary compositions (e.g., percentages of prey biomasses), researchers have scaled the DNA-based frequency of occurrence of major prey groups so that their normalized frequency of occurrence sums to 100%. Unfortunately, such an approach is problematic as priors stemming from binomial, DNA-based data do not truly reflect quantitative information about the consumer's diet and may skew the posterior distribution of prey quantities as a result. Therefore, we present a novel approach to incorporate DNA-based dietary information into Bayesian stable isotope mixing models that preserves the binomial nature of DNA-based results. This approach uses community-wide frequency of occurrence or logistic regression-based estimates of prey occurrence to dictate the probability that each prey group is included in each mixing model iteration, and, in turn, the probability that each iteration's results are included in the posterior distribution of prey composition possibilities. Here, we demonstrate the utility of this method by using it to quantify the prey composition of nestling Louisiana waterthrush (Parkesia motacilla).
Exposure to stressors typically suppresses reproductive processes, including the expression of se... more Exposure to stressors typically suppresses reproductive processes, including the expression of sexual behaviour. However, many animal species breed in extreme conditions where opportunities to mate in a given season are limited. In such species, stress‐induced suppression of reproduction would be maladaptive, especially if they also have short lifespans. Species with longer lifespans, but still limited mating opportunities in a given season, may be able to withstand a few missed breeding opportunities. We tested whether capture and handling would suppress male sexual behaviour in spotted salamanders (Ambystoma maculatum), a species with an explosive mating strategy but a relatively long lifespan. Males were captured as they migrated to breeding sites and were handled in a manner known to induce an increase in plasma corticosterone, a component of the stress response. Thirty min later, each male was paired with a freshly captured female for 60 min. Handled males deposited significantly more spermatophores than did control males. The mechanism for the increased sexual behaviour is unknown but may involve handling‐induced changes in stress hormones or reproductive hormones. Regardless of the mechanism whereby handling increased male sexual behaviour, our results support the hypothesis that stressors do not suppress male mating behaviour in a long‐lived species with limited opportunities to mate.
Providing taxonomically precise dietary characterisations for freshwater fish species is critical... more Providing taxonomically precise dietary characterisations for freshwater fish species is critical for gaining a deeper understanding of the trophic dynamics present in freshwater ecosystems. However, our current understanding of freshwater trophic ecology has relied almost entirely upon direct observation of foraging attempts or morphological identification of partially digested prey. Due to the limitations of morphological dietary characterisations of soft‐bodied arthropod prey, these techniques offer dietary descriptions that can lack satisfactory taxonomic resolution and may bias our interpretations of freshwater food webs. Recent advancements in DNA‐based prey identification have allowed for species‐level prey characterisations for many terrestrial insectivores, although these techniques have seldom been applied to understand the diets of freshwater fish. This study used DNA metabarcoding with high‐throughput, next‐generation sequencing to provide species‐level descriptions of prey composition for three naturally reproducing, syntopic freshwater trout species. Our study supports previous findings that suggested that brook trout (Salvelinus fontinalis), brown trout (Salmo trutta), and rainbow trout (Oncorhynchus mykiss) are generalist predators that display a high degree of seasonal dietary flexibility. Prey composition varied significantly across sampling periods, with detection frequency of terrestrial prey greater in the spring/summer period compared to the autumn period. Pollution‐sensitive aquatic macroinvertebrates were detected frequently across both sampling periods, highlighting the importance of high‐quality streams that support such arthropod prey. DNA metabarcoding also detected a high richness of soft‐bodied, Lepidoptera prey species, a taxonomic group that has been largely underrepresented in previous trout dietary studies that used traditional morphological techniques. This study demonstrates the applicability of dietary DNA metabarcoding for the detection and species‐level identification of arthropods found in freshwater fish lavage samples and highlights the importance of taxonomically precise techniques when attempting to better understand trophic interactions within freshwater communities.
Benthic trawling was compared to standard shoreline night electrofishing within two pools of the ... more Benthic trawling was compared to standard shoreline night electrofishing within two pools of the Allegheny River navigation system. The combined methods captured 53 fish species and two hybrids—42 species by electrofishing and 27 species by trawling. Although benthic trawling captured fewer species. it was very effective in sampling species of the family Percidae. The results verify that benthic trawling is an effective supplemental method for assessing the fish communities of large rivers where other standard sampling techniques may severely under-represent or fail to detect important and abundant benthic fishes.
Proceedings of the American Philosophical Society: Held at Philadelphia for Promoting Useful Knowledge, 2003
... Rd. 232), 14.4 airmi. NE Leesburg, Lee Co., Georgia, 19 August 2002, BA Porter and Randi D. R... more ... Rd. 232), 14.4 airmi. NE Leesburg, Lee Co., Georgia, 19 August 2002, BA Porter and Randi D. Rotjan. 3. Notropis metallicus, GMNH 3422, adult male, 49 mm SL. ... 65, 1.9 airmi. NNE Hosford, Liberty Co., Florida, 22 July 2001, BA Porter and Randi D. Rotjan. Photos by BA Porter. ...
Abstract Human disturbance increases the invasi-bility of lotic ecosystems and the likelihood of ... more Abstract Human disturbance increases the invasi-bility of lotic ecosystems and the likelihood of hybridization between invasive and native species. We investigated whether disturbance contributed to the invasion of red shiner (Cyprinella lutrensis) and their hybridization with native ...
Abstract Within the upper Ohio River watershed, 3 Etheostoma darter species in the subgenus Notho... more Abstract Within the upper Ohio River watershed, 3 Etheostoma darter species in the subgenus Nothonotus have been documented in disjunct populations and were listed as threatened or endangered in Ohio and Pennsylvania. Tailwater habitat below navigation lock and dam (L/D) installations has been shown to contain diverse darter assemblages. Etheostoma camurum (Bluebreast Darter), E. maculatum (Spotted Darter), and E. tippecanoe (Tippecanoe Darter) often live in similar habitats; thus, we hypothesized that all 3 were occupying tailwater habitat below navigational L/Ds. Electrified benthic trawling verified Bluebreast Darter and Tippecanoe Darter below 8 L/D installations and at water depths varying from 1.4 m to 4.5 m and 1.4 m to 5.9 m, respectively. Spotted Darter was only found below 1 L/D. In the Ohio River, benthic trawling documented Bluebreast Darter and Tippecanoe Darter utilizing habitat located within deposition zones and areas above and below islands. Analysis of contemporary and historic distribution data shows that Bluebreast Darter and Tippecanoe Darter now span large sections of the river, but the range of Spotted Darter is more limited and warrants close monitoring. Our study confirms the effectiveness of utilizing benthic trawling in non-wadeable rivers to survey for benthic species such as river-inhabiting darters.
... subgenus Ulocentra, and 11 members of the proposed sister subgenus Etheostoma were investigat... more ... subgenus Ulocentra, and 11 members of the proposed sister subgenus Etheostoma were investigated with 1033 base pairs of mitochondrial DNA sequence data and 54 osteological characters ... Phylogeography was used to interpret the genetic variation between populations ...
Synopsis The introduction of laboratory methods to animal dietary studies has allowed researchers... more Synopsis The introduction of laboratory methods to animal dietary studies has allowed researchers to obtain results with accuracy and precision, not possible with observational techniques. For example, DNA barcoding, or the identification of prey with taxon-specific DNA sequences, allows researchers to classify digested prey tissues to the species-level, while stable isotope analysis paired with Bayesian mixing models can quantify dietary contributions by comparing a consumer's isotopic values to those derived from their prey. However, DNA-based methods are currently only able to classify, but not quantify, the taxa present in a diet sample, while stable isotope analysis can only quantify dietary taxa that are identified a priori as prey isotopic values are a result of life history traits, not phylogenetic relatedness. Recently, researchers have begun to couple these techniques in dietary studies to capitalize on the reciprocal benefits and drawbacks offered by each approach, with some even integrating DNA-based results directly into Bayesian mixing models as informative priors. As the informative priors used in these models must represent known dietary compositions (e.g., percentages of prey biomasses), researchers have scaled the DNA-based frequency of occurrence of major prey groups so that their normalized frequency of occurrence sums to 100%. Unfortunately, such an approach is problematic as priors stemming from binomial, DNA-based data do not truly reflect quantitative information about the consumer's diet and may skew the posterior distribution of prey quantities as a result. Therefore, we present a novel approach to incorporate DNA-based dietary information into Bayesian stable isotope mixing models that preserves the binomial nature of DNA-based results. This approach uses community-wide frequency of occurrence or logistic regression-based estimates of prey occurrence to dictate the probability that each prey group is included in each mixing model iteration, and, in turn, the probability that each iteration's results are included in the posterior distribution of prey composition possibilities. Here, we demonstrate the utility of this method by using it to quantify the prey composition of nestling Louisiana waterthrush (Parkesia motacilla).
Exposure to stressors typically suppresses reproductive processes, including the expression of se... more Exposure to stressors typically suppresses reproductive processes, including the expression of sexual behaviour. However, many animal species breed in extreme conditions where opportunities to mate in a given season are limited. In such species, stress‐induced suppression of reproduction would be maladaptive, especially if they also have short lifespans. Species with longer lifespans, but still limited mating opportunities in a given season, may be able to withstand a few missed breeding opportunities. We tested whether capture and handling would suppress male sexual behaviour in spotted salamanders (Ambystoma maculatum), a species with an explosive mating strategy but a relatively long lifespan. Males were captured as they migrated to breeding sites and were handled in a manner known to induce an increase in plasma corticosterone, a component of the stress response. Thirty min later, each male was paired with a freshly captured female for 60 min. Handled males deposited significantly more spermatophores than did control males. The mechanism for the increased sexual behaviour is unknown but may involve handling‐induced changes in stress hormones or reproductive hormones. Regardless of the mechanism whereby handling increased male sexual behaviour, our results support the hypothesis that stressors do not suppress male mating behaviour in a long‐lived species with limited opportunities to mate.
Providing taxonomically precise dietary characterisations for freshwater fish species is critical... more Providing taxonomically precise dietary characterisations for freshwater fish species is critical for gaining a deeper understanding of the trophic dynamics present in freshwater ecosystems. However, our current understanding of freshwater trophic ecology has relied almost entirely upon direct observation of foraging attempts or morphological identification of partially digested prey. Due to the limitations of morphological dietary characterisations of soft‐bodied arthropod prey, these techniques offer dietary descriptions that can lack satisfactory taxonomic resolution and may bias our interpretations of freshwater food webs. Recent advancements in DNA‐based prey identification have allowed for species‐level prey characterisations for many terrestrial insectivores, although these techniques have seldom been applied to understand the diets of freshwater fish. This study used DNA metabarcoding with high‐throughput, next‐generation sequencing to provide species‐level descriptions of prey composition for three naturally reproducing, syntopic freshwater trout species. Our study supports previous findings that suggested that brook trout (Salvelinus fontinalis), brown trout (Salmo trutta), and rainbow trout (Oncorhynchus mykiss) are generalist predators that display a high degree of seasonal dietary flexibility. Prey composition varied significantly across sampling periods, with detection frequency of terrestrial prey greater in the spring/summer period compared to the autumn period. Pollution‐sensitive aquatic macroinvertebrates were detected frequently across both sampling periods, highlighting the importance of high‐quality streams that support such arthropod prey. DNA metabarcoding also detected a high richness of soft‐bodied, Lepidoptera prey species, a taxonomic group that has been largely underrepresented in previous trout dietary studies that used traditional morphological techniques. This study demonstrates the applicability of dietary DNA metabarcoding for the detection and species‐level identification of arthropods found in freshwater fish lavage samples and highlights the importance of taxonomically precise techniques when attempting to better understand trophic interactions within freshwater communities.
Benthic trawling was compared to standard shoreline night electrofishing within two pools of the ... more Benthic trawling was compared to standard shoreline night electrofishing within two pools of the Allegheny River navigation system. The combined methods captured 53 fish species and two hybrids—42 species by electrofishing and 27 species by trawling. Although benthic trawling captured fewer species. it was very effective in sampling species of the family Percidae. The results verify that benthic trawling is an effective supplemental method for assessing the fish communities of large rivers where other standard sampling techniques may severely under-represent or fail to detect important and abundant benthic fishes.
Proceedings of the American Philosophical Society: Held at Philadelphia for Promoting Useful Knowledge, 2003
... Rd. 232), 14.4 airmi. NE Leesburg, Lee Co., Georgia, 19 August 2002, BA Porter and Randi D. R... more ... Rd. 232), 14.4 airmi. NE Leesburg, Lee Co., Georgia, 19 August 2002, BA Porter and Randi D. Rotjan. 3. Notropis metallicus, GMNH 3422, adult male, 49 mm SL. ... 65, 1.9 airmi. NNE Hosford, Liberty Co., Florida, 22 July 2001, BA Porter and Randi D. Rotjan. Photos by BA Porter. ...
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