Stability, persistence and habitat associations of the pearl darter Percina aurora in the Pascagoula River System, southeastern USA

Worldwide, cryptic species, which comprise two or more distinct species that are classified as one due to their morphological similarity, are more common than previously thought. In South Africa, the chubbyhead barb, Enteromius anoplus (Weber, 1897), is the most widespread freshwater fish species. The widespread occurrence of this species across different river basins raised questions on its taxonomic status due to the likely occurrence of hidden diversity. This further raised the need to evaluate the ecological patterns associated with likely occurrence of such hidden diversity. Phylogenetic analyses of the cytochrome b gene of E. anoplus populations across South Africa revealed the occurrence of four genetically distinct species. These findings supported the restoration Enteromius cernuus (Barnard 1943) stat. rev. from the Olifants River system; the restoration of Enteromius anoplus sensu stricto (Weber 1897) stat. rev. from the Gouritz River system; the redescription of Enteromius oraniensis (Barnard 1943) stat. rev. from the Orange River system; and the description of a new species, Enteromius mandelai sp. nov. from the Eastern Cape rivers. Analyses of morphometric and meristic data revealed that these species were differentiated based on barbel length and number of lateral line scales. Ecological studies on Enteromius mandelai were conducted within headwater streams of major river systems in the Eastern Cape region. These headwater streams had different catchment characteristics ranging from near-natural to anthropogenically-perturbed mainly due to agriculture-related disturbances and invasion of riparian zones by non-native plants. Stable isotope analysis provided evidence of trophic plasticity for E. mandelai across the different headwater streams. Specifically, E. mandelai exhibited large isotopic niches in agriculture-disturbed headwater streams, whereas small isotopic niches were observed in headwater streams invaded by non-native plants. Because of the evidence of trophic plasticity for E. mandelai, this study further hypothesized that this species would exhibit variable environmental niche patterns related to its distribution, abundance and the presence of contra-specifics due to different abiotic factors across its range. Enteromius mandelai was generally most abundant at sites with high total dissolved solids and sand substratum, which was characteristic of large pool habitats, and least abundant at sites with high turbidity. In the Great Fish River, E. mandelai occurred as the only species in most headwater sites, whereas in the Keiskamma and Buffalo River systems, it co-occurred with Amatolacypris trevelyani and Sandelia bainsii. Enteromius mandelai was, nevertheless, found to be ubiquitous together with having wide environmental niches, and exhibited no discernible patterns in its habitat associations. The taxonomic re-evaluation of the E. anoplus complex, which provided evidence of the existence of new species, has implications for the biogeographic zonation of the ichthyofauna of the Cape Fold Ecoregion (CFE), Amathole-Winterberg Highlands Ecoregion (AWHE) and the Southern Temperate Highveld Ecoregion (STHE). For example, the currently recognised southern limit of the STHE, which encompasses the AWHE, is based on the occurrence of E. anoplus, Enteromius pallidus and Labeo umbratus. However, evidence from this and other recent studies indicate the occurrence of either new species or distinct lineages in the southern-most section of the STHE, which is consistent with the patterns observed in the CFE. Comparison of taxonomic composition showed that species in the eastern part of the CFE were similar to species in the AWHE and the southern-most section of the STHE. Because of the close affinities among most of the new taxa in these regions, this study proposes that the current delimitation of the CFE should be reviewed by extending it to include the AWHE and sections of the STHE.

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Anthropogenic stress alters community concordance at the river-riparian interface

10.7287/peerj.preprints.798v1 ◽

2015 ◽

Author(s):

Jonathan D Tonkin ◽

Stefan Stoll ◽

Sonja C Jähnig ◽

Peter Haase

Keyword(s):

Community Structure ◽

Spatial Scales ◽

River System ◽

Habitat Associations ◽

Carabid Beetles ◽

Anthropogenic Stress ◽

Spatial Gradients ◽

Resource Requirements ◽

Surrogate Taxa ◽

Community Concordance

Organisms often respond in similar ways to environmental or spatial gradients, particularly at large spatial scales, but patterns at finer scales and across ecotones are less certain. It is important to understand these relationships at multiple spatial scales, as managers often need suitable surrogate taxa for conservation and monitoring purposes. We explored whether community concordance at the river-riparian interface was decoupled by increasing anthropogenic stress (a gradient of local land-use intensity) at 15 sites over three years within the LTER site, Rhine-Main Observatory, a low mountain river system in central Germany. We assessed concordance between four organism groups: riparian spiders and carabid beetles, benthic macroinvertebrates, and combined aquatic macrophytes and riparian plants. This represented three different linkages: (1) predator-prey, (2) direct competition, and (3) habitat associations. While there were no correlations in richness patterns, multivariate community structure was highly concordant between all groups. Anthropogenic stress strongly reduced links between riparian spiders and carabid beetles, likely resulting from their shared resource requirements. However, increasing concordance occurred between plants and other groups. We posit that patterns may be resulting from two processes: (1) linkages between directly competing species decouple with increasing anthropogenic stress, and (2) stronger coupling may occur between habitat providers and dependent species when overall habitat complexity is reduced. These results highlight the complex manner in which anthropogenic stress can influence ecosystems and the importance of considering community structure when exploring biodiversity patterns in basic and applied ecological research, particularly at small scales and for surrogate taxa development.

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Mapping and Modeling the Distribution, Abundance, and Habitat Associations of the Endangered Fat Threeridge in the Apalachicola River System

Journal of Fish and Wildlife Management ◽

10.3996/032019-jfwm-021 ◽

2019 ◽

Vol 10 (2) ◽

pp. 653-675

Author(s):

Adam J. Kaeser ◽

Reuben Smit ◽

Michael Gangloff

Keyword(s):

River Mouth ◽

River System ◽

Habitat Associations ◽

Side Scan Sonar ◽

Habitat Monitoring ◽

Fine Sediments ◽

Smooth Plane ◽

Apalachicola River ◽

Future Population ◽

Mussel Habitat

Abstract Large, Coastal Plain rivers of the southeastern United States contain some of the most diverse freshwater communities in North America; however, surveying the fauna of these large rivers presents numerous logistical and statistical challenges. We assessed the contemporary distribution, abundance, and habitat associations of the endangered fat threeridge mussel Amblema neislerii throughout the Apalachicola River system in northwestern Florida. To achieve this goal, we used side scan sonar to map the distribution of mesohabitats and conducted a system-wide, quantitative survey to define mussel habitat associations. We then used habitat and mussel data to develop predictive models of spatial distribution and to estimate the abundance of fat threeridge across the entire Apalachicola River system. Findings revealed a broadly distributed (i.e., 128 river kilometers occupied), robust population of approximately 9 million individuals (95% CI = 5–12 million), with a center of distribution (i.e., where abundance and occurrence were highest) approximately 45–80 river kilometers upstream of the river mouth. Fat threeridge primarily occupy fine sediment mesohabitats characterized by smooth/plane bedforms that are clearly definable via sonar habitat mapping. We hypothesize that this species may be particularly sensitive to the availability of stable, fine sediments during one or more critical life history phases and that the availability of this habitat may explain its restricted distribution in tributary rivers. Our study provides a quantitative, replicable foundation upon which future population and habitat monitoring can be based.

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Anthropogenic stress alters community concordance at the river-riparian interface

10.7287/peerj.preprints.798 ◽

2015 ◽

Author(s):

Jonathan D Tonkin ◽

Stefan Stoll ◽

Sonja C Jähnig ◽

Peter Haase

Keyword(s):

Community Structure ◽

Spatial Scales ◽

River System ◽

Habitat Associations ◽

Carabid Beetles ◽

Anthropogenic Stress ◽

Spatial Gradients ◽

Resource Requirements ◽

Surrogate Taxa ◽

Community Concordance

Organisms often respond in similar ways to environmental or spatial gradients, particularly at large spatial scales, but patterns at finer scales and across ecotones are less certain. It is important to understand these relationships at multiple spatial scales, as managers often need suitable surrogate taxa for conservation and monitoring purposes. We explored whether community concordance at the river-riparian interface was decoupled by increasing anthropogenic stress (a gradient of local land-use intensity) at 15 sites over three years within the LTER site, Rhine-Main Observatory, a low mountain river system in central Germany. We assessed concordance between four organism groups: riparian spiders and carabid beetles, benthic macroinvertebrates, and combined aquatic macrophytes and riparian plants. This represented three different linkages: (1) predator-prey, (2) direct competition, and (3) habitat associations. While there were no correlations in richness patterns, multivariate community structure was highly concordant between all groups. Anthropogenic stress strongly reduced links between riparian spiders and carabid beetles, likely resulting from their shared resource requirements. However, increasing concordance occurred between plants and other groups. We posit that patterns may be resulting from two processes: (1) linkages between directly competing species decouple with increasing anthropogenic stress, and (2) stronger coupling may occur between habitat providers and dependent species when overall habitat complexity is reduced. These results highlight the complex manner in which anthropogenic stress can influence ecosystems and the importance of considering community structure when exploring biodiversity patterns in basic and applied ecological research, particularly at small scales and for surrogate taxa development.

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Nearshore Fish Species Richness and Species–Habitat Associations in the St. Clair–Detroit River System

Water ◽

10.3390/w13121616 ◽

2021 ◽

Vol 13 (12) ◽

pp. 1616

Author(s):

Corbin D. Hilling ◽

Jason L. Fischer ◽

Jason Ross ◽

Taaja R. Tucker ◽

Robin L. DeBruyne ◽

...

Keyword(s):

Species Richness ◽

Fish Species ◽

Habitat Restoration ◽

Aquatic Macrophyte ◽

River System ◽

Habitat Associations ◽

Individual Species ◽

Theoretic Approach ◽

Detroit River ◽

Habitat Variables

Shallow water riparian zones of large rivers provide important habitat for fishes, but anthropogenic influences have reduced the availability and quality of these habitats. In the St. Clair–Detroit River System, a Laurentian Great Lakes connecting channel, losses of riparian habitat contributed to impairment of fish populations and their habitats. We conducted a seine survey annually from 2013 to 2019 at ten sites in the St. Clair and Detroit rivers to assess riparian fish communities, and to identify habitat attributes associated with fish species richness and catches of common species. We captured a total of 38,451 fish representing 60 species, with emerald shiner Notropis atherinoides composing the largest portion of the catch. We used an information-theoretic approach to assess the associations between species richness and catches of 33 species with habitat variables (substrate, shoreline vegetation types, and aquatic macrophyte richness). Sand, cobble, and algal substrates and shoreline vegetation were important predictors of species richness based on a multimodel inference approach. However, habitat associations of individual species varied. This work identified manageable habitat variables associated with species richness, while identifying potential tradeoffs for individual species. Further, this work provides baselines for development and evaluation of fish community and shoreline habitat restoration goals.

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