Nested-subset structure of larval odonate assemblages in the Enoree River basin, USA (original) (raw)
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The Structure of Larval Odonate Assemblages in the Enoree River Basin of South Carolina
Southeastern Naturalist, 2002
Odonate larvae were collected at 127 sites in the Enoree River and nine of its tributaries in the summers of 1999 and 2000. Mean odonate abundance, species richness, and Simpson's diversity were compared across tributaries and the main channel of the Enoree River with one-way ANOVA. These indices were significantly lower in Brushy Creek, Rocky Creek, and the Upper Enoree than in the other streams (Tukey multiple comparison test, p < 0.05). These three streams also differed from the others in species composition (MANOVA p < 0.0001), as measured by changes in the relative abundances of the five most abundant species: Progomphus obscurus, Boyeria vinosa, Macromia illinoiensis, Cordulegaster maculata, and Ophiogomphus mainensis. For example, O. mainensis was nearly absent from Brushy, Rocky, and the Upper Enoree, but was a significant component of the assemblages in other streams. Cordulegaster maculata was rare in Rocky Creek but dominated the Upper Enoree where other species were less abundant. Brushy, Rocky, and the Upper Enoree are areas of either rapid residential development or known industrial contamination. The different structure of odonate assemblages in these streams may reflect the impact of these local anthropogenic effects.
2002
This thesis explored the distributions and life histories of dragonflies and damseiflies (Insecta: Odonata) of the riverine wetlands of the Willamette Valley in western Oregon, USA. Odonate species distributions were characterized over two seasonsin the autumn of 2000 and the spring of 2001at twenty-seven wetlands located throughout the valley. Distributions of nymphs and adults were compared with wetland habitat conditions that may affect odonate diversity. Odonate nymph and adult distributions were analyzed through Hierarchical Agglomerative cluster analysis (HA). HA identified discrete clusters of sites based on the distributions of species in the genera Aeshna, Erythemis, Lestes, Libellula, Pachydiplax, Sympetrum and Trainea. To identify habitat associations with odonate species, nymph and adult data were analyzed by Non-metric Multidimensional Scaling (NMS). NMS revealed that odonate distributions are associated with site hydrology, water depth and temperature, the presence of large emergent plants (e.g. Typha latfolia), the presence of fish, and surrounding landcover. These data will provide guidance for wetland managers in the use of odonates as indicators of wetland health. To further examine the relationship between odonate species and their wetland habitats, quantitative life history data for the 27 odonate species were analyzed to determine functional associations between species attributes and the Abstract approved
International Journal of Odonatology, 2020
Dragonflies (Insecta: Odonata) use both aquatic and terrestrial ecosystems, and the abundance and diversity of odonates should be good indicators of habitat integrity. To determine which environmental variables affect odonates, we sampled adult dragonflies three times at 12 sites in Pickens and Greenville Counties, SC, USA, in different habitats, at different spatial scales, across a landscape gradient from intact forest to urban locations. At each site, we established two 2 m × 20 m plots along the shoreline of each aquatic habitat. We sampled dragonflies in ten 2 m × 2 m subplots/plot, described the vegetation and substrate in these subplots and adjacent aquatic subplots, and measured the percent cover of different landforms within 500 m of each plot center. Using nested ANOVA and Akaike information criteria models, habitat type and correlating environmental variables (substrate type and bank vegetation) were the best predictors of community structure at all spatial scales. Streams and rivers had fewer individuals and species than lakes, and had a nested subset of species found in lake communities. Landscape elements were also important, with indices declining as barren land and grasslands increased. At the largest scale, anthropogenic changes to the landscape had mixed effects. Small habitats isolated in urban areas had a significantly depauperate, nested subset of species found in communities inhabiting larger natural areas. However, odonate abundance and diversity was highest at human-made lakes and ponds, suggesting that these anthropogenic features help maintain odonate communities.
Freshwater Biology, 2005
1. Studies in several parts of the world have examined variation in univariate descriptors of macroinvertebrate assemblage structure in perennially flowing stony streams across hierarchies of spatial scale using nested analyses of variance. However, few have investigated whether this spatial variation changes with time or whether these results are representative of habitats other than riffles or of other stream types, such as intermittently flowing streams. 2. We describe patterns in taxon richness and abundance from two sets of samples from stony streams in the Otway Range and the Grampians Range, Victoria, Australia, collected using hierarchical designs. Sampling of riffles was repeated in the Otways, to determine whether spatial patterns were consistent among times. In the Grampians, spatial patterns were compared between intermittent and perennially flowing streams (stream type) by sampling pools. 3. In the Otways streams, most variation in the dependent variables occurred between sample units. Patterns of variation among the other scales (streams, segments, riffles, groups of stones) were not consistent between sampling times, suggesting that they may have little ecological significance. 4. In the Grampians streams, variation in macroinvertebrate taxon richness and abundance differed significantly between replicate streams within each stream type but not between stream types or pools. The largest source of variation in taxon richness was stream type. Little variation occurred among sample units. 5. The pattern of most variation occurring among sample units is robust both to differences in the method of sampling and different dependent variables among studies and increasingly appears to be a property of riffles in stony, perennial upland streams. High variation among sample units (residual variation) limits the explanatory power of linear models and therefore, where samples are from a single sampling time, small but significant components of variation are unlikely to represent features of assemblage structure that will be stable over time.
Invertebrate distribution across nested geomorphic features in braided-river landscapes
Freshwater Science, 2013
River landscapes are increasingly viewed as a collection of nested geomorphic features, the hydrological effects of which juxtapose to create a mosaic of aquatic habitat conditions. We examined how the combined hydrological influences of stream reaches and gravel bars affect the composition of hyporheic invertebrate assemblages along the longitudinal and vertical dimensions of river landscapes. We worked in 12 braided-river valley segments of tributaries to the Rhô ne River, France. Valley segments were bounded downstream by geological knickpoints so that bedform-induced exchange flows beneath gravel bars and riffles were predictably embedded in exchange flows occurring at the valley-segment scale. In upstream reaches (UR) and downstream reaches (DR) of each valley segment, we collected invertebrates at the heads and tails of gravel bars in the hyporheic zone and at the upstream and downstream ends of riffles in surface channels adjacent to the bars. Patterns of vertical hydraulic gradient and specific conductance and the resulting spatial heterogeneity of temperature, dissolved O 2 and particulate organic C suggested that DR were points of flow convergence and water mixing. Specific conductance increased and temperature decreased more steeply along gravel bars in DR, indicating that water from long hyporheic flow paths or lateral aquifers was discharging at the tails of bars in DR. Density hotspots for insect larvae corresponded to hyporheic patches at the heads of bars in DR, which received the highest organic matter inputs from localized downwelling of surface water and were not affected by inputs of cold water from hyporheic flow paths or lateral aquifers. Density of epigean taxa at the tails of bars decreased more steeply with depth in DR than in UR, and density of hypogean taxa increased more steeply. Viewing local hyporheic assemblages as the outcome of a series of environmental filters operating over multiple exchange flows induced by nested geomorphic features provides a general framework that may foster our understanding of biodiversity patterns in river landscapes.
Canadian Journal of Fisheries and Aquatic Sciences, 2001
Tributary confluences are sites along a main channel where, because of the introduction of water and (or) sediment, the water volume, bed sediment character, and water quality of the mainstream can change abruptly. These shifts ensure that abiotic gradients seldom vary smoothly or continuously for distances of more than 10 0 -10 2 km along any river system. The ways in which tributaries and related sediment recruitment points structure longitudinal changes in physical habitat are examined. Variables of importance to stream biota are affected and, in turn, it is suggested that the arrangement of tributaries and related features is an important control on the longitudinal organisation of macroinvertebrate benthos at moderate spatial scales. A new model is presented that stresses the importance of hydrological and sedimentological networks for organising lotic fauna. The link discontinuity concept emphasises the discontinuous nature of lotic ecosystem gradients, addresses the importance of tributaries in unregulated as well as regulated rivers, and extends, to its logical conclusion, the limited recognition of tributary influence in the river continuum concept. A case study from British Columbia, Canada, illustrates the general merit of the new model.
The immature Odonata community is used to diagnose and monitor impacts on aquatic environments. Degraded environments, with a wide range of environmental variables, usually present highly resilient species. Here we present a highly diverse immature Odonata community, collect with great sample effort. In doing so, we were able to show that these altered and natural environments have similar immature Odonata communities, and pH was the only abiotic variable affecting the system and the community. The community also changes with seasonal variation, because rains modify the river flow. Furthermore, the ecological integrity of the streams was influenced by anthropogenic activities, changing the dynamics of the Odonata communities. Two genera, Brechmorhoga and “Unidentified genus 1”, are indicators of altered environments, so they can be used as bioindicator in others monitoring environmental evaluations.