Stock discrimination and connectivity assessment of yellowfin seabream (Acanthopagrus latus) in northern South China Sea using otolith elemental fingerprints

Connectivity between fish stocks is fundamental to the understanding of population dynamics and the implementation of sustainable fisheries management. Otolith microchemistry is a promising tool as it can provide information on the continuous growth of otoliths and the environmental effects on otolith composition. Such elemental fingerprints can help distinguish different stocks or life history stages, identify the origins or nursery areas of fish, and assess population structure. In this study, we examined the stock discrimination and spatial connectivity of cage-cultured and wild stocks of yellowfin seabream (Acanthopagrus latus) from the coastal waters of Shantou, Yangjiang, and Zhanjiang in China southern province Guangdong during 2012–2014, based on otolith trace-elemental signatures using multivariate statistical analysis and machine learning approaches. The concentrations of 13 elements (⁷Li, ²³Na, ²⁴Mg, ⁴⁰Ca, ⁵⁵Mn, ⁵⁶Fe, ⁵⁹Co, ⁵⁹Ni, ⁶⁴Cu, ⁶⁵Zn, ⁸⁸Sr, ¹²²Sb, and ¹³⁷Ba) in the natal spot of fish otoliths, representing the embryonic and paralarval stages of fish, were analyzed using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Stepwise discriminant analysis and random forests were used to distinguish the cultured and wild stocks of yellowfin seabream, and non-metric multidimensional scaling (NMDS) and cluster analysis were used to determine the spatial variation and connectivity of yellowfin seabream stocks. Overall, the cultured and wild stocks of yellowfin seabream could be identified with classification accuracy of 80.7% and 99.2% by using stepwise discriminant analysis and random forests respectively. When we compared site difference between cultured and wild stocks (site × stock interactions), the classification success was 60.4% for stepwise discriminant analysis and 85.7% for random forests. The misclassification of cultured and wild stocks within the three sites suggested the spatial connectivity between stocks and among sampling locations. Our findings suggested that the three wild stocks of yellowfin seabream from Guangdong coastal waters could be considered as one unit for management, and the difference between cultured and wild stocks was significant for yellowfin seabream from Shantou and Yangjiang, but less significant for yellowfin seabream from Zhanjiang. This study demonstrated that otolith elemental fingerprints can help improve our knowledge on the spatial connectivity, population structure, and life history of fish stocks, and random forests can be a useful tool for identifying cultured and wild stocks compared to the traditional stepwise discriminant analysis.     

The submersed macrophyte communities of adirondack lakes (New York,U.S.A.) of varying degrees of acidity

The submersed macrophyte communities of nine high-altitude oligotrophic lakes in the Adirondack Mountain region of upstate New York were characterized in detail in terms of percent cover of each species. The pH of these clear-water lakes ranged from 6.9 to 4.4 and the acid neutralizing capacity ranged from 91 μeq 1^?1 to ?38 μeq l^?1. The degree of acidity covaried with lower total ion content and nutrient status. The dominant species in the circumneutral lakes and in the acidic lakes were the same, with several Utricularia species being the major component of the bottom cover. Species richness and diversity were lower in the acidic lakes (pH < 5.5). The plants found in the acidic lakes were typical of oligotrophic systems in general, regardless of pH, and similar to those found in lake surveys in Scandinavia and Eastern Canada. Potamogeton confervoides Reichenb., Scirpus subterminalis Torr., Sphagnum spp. and Utricularia geminiscapa Benj. were the only species that were primarily exclusive to the acidic lakes surveyed. In contrast to the results of Scandinavian studies, Sphagnum was found to be a major component of the plant cover in only two of the five acidic lakes.     

No biotic homogenisation across decades but consistent effects of landscape position and pH on macrophyte communities in boreal lakes

It has been predicted that spatial beta diversity shows a decreasing trend in the Anthropocene due to increasing human impact, causing biotic homogenisation. We aimed to discover if vascular aquatic macrophyte communities show different spatial patterns in beta diversity in relation to land use and environmental characteristics in different decades from 1940s to 2010s. We aimed to discover if spatial structures differ between species-, phylogeny- and functional-based beta diversity. We used presence–absence data of aquatic macrophytes from five decades from small boreal lakes. We utilized generalised dissimilarity modelling to analyse spatial patterns in beta diversity in relation to environmental gradients. We found that lake elevation and pH were the most important variables in each decade, while land use was not particularly important in shaping beta diversity patterns. We did not find signs of a decreasing trend in spatial beta diversity in our study area during the past 70 yr. We did not find signs of either biotic homogenisation or biotic differentiation (taxonomic, phylogenetic or functional). Vascular aquatic macrophyte communities showed only slightly different beta diversity patterns in relation to human impact across decades. The patterns of different facets of beta diversity diverged only slightly from each other. Lake position in the landscape, reflecting both natural connectivity and lake characteristics, explained the patterns found in beta diversity, probably because our study area has faced only modest changes in land use from 1940s to 2010s when compared globally. Our study highlights the fact that biotic homogenisation is not an unambiguous process acting similarly at all spatial and temporal scales or in different environments and different organism groups.     

A numeric, geographic and structural analysis of the Hakea falcata group (Proteaceae)

Specimens placed earlier under Hakea falcata are shown to comprise four species: H. falcata, H. ulicina, H. erecta and H. cygna. Failure by previous authors to cite types, or the correct type, led to the placement of subsequently collected H. falcata specimens (sensu R. Br.) under H. ambigua in Australian herbaria. The relationships of the five taxa are explored phenetically using metric multidimensional scaling and cluster analysis. Flowers provide the best diagnostic characters for separating H. falcata and H. ambigua , while fruits and seeds are better for H. erecta and H. cygna. All species are endemic to SW Australia, except H. ulcina , which is endemic to SE Australia. Two subspecies of H. cygna are recognized, based on populations with disparate leaf morphology. Each taxon has a distinctive leaf anatomy with all but H. falcata highly sclerophyllous.     

Temporal coherence in the limnology of a suite of lakes in Wisconsin, U.S.A.

SUMMARY. 1. Temporal coherence between pairs of lakes over 7 years was measured for thirty-seven limnological variables in seven lakes at the North Temperate Lakes Long Term Ecological Research site in Northern Wisconsin. This analysis tested. First, whether lakes more similar in exposure to the atmosphere were more temporally coherent than lakes which differed more in exposure and, second, whether temporal coherence in lakes progressively decreased from variables more directly influenced by climatic factors such as thermal and hydrologic properties, to those chemical and biological properties which may be less directly influenced by climatic factors. 2. The lakes were a heterogeneous set in respect to exposure to climatic factors as estimated by the ratio of‘lake area/mean depth’and by other morphometric features, and they also differed in their position in the landscape, fertility and fish assemblages. Limnological variables formed a progression from those expected to respond directly to climatic factors to those which would not. They ranged from water level and temperatures to chemical variables such as pH, calcium concentrations and total dissolved phosphorus to biological variables such as chlorophyll concentrations, invertebrate and fish abundances. 3. Coherence was estimated by the correlation between lake pairs for each of the different variables. The mean correlation and the percentage of strong correlations were calculated for each lake pair across all variables, and for each variable across all lake pairs, and both measures of coherence gave similar answers to the questions posed above. 4. Temporal coherence between takes was higher for lakes similar in their exposure to climatic factors; mean correlation (r?) being +0.3 to +0.7 for these lakes and <+0.3 for lakes not similar in exposure. None of the lake pairs had high coherence across all variables. 5. Temporal coherence between lakes was greater for limnological variables directly influenced by climatic factors than for variables either indirectly affected by climate or complexly influenced by other types of factors. Water-level variables had a coherence near 1, r?=0.9. All biological variables had low coherence, some near r?=0.0. Chemical variables more likely to be influenced directly by climatic factors appeared to be more coherent than those more influenced by hydrology or biology. Most silica and phosphorus variables had coherences less than r?=0.15. 6. Coherence was not as strongly related to similarity in landscape position as it was to similarity in exposure to climatic factors, and was not jelated to the proximity of the lake pairs or to their similarity in fertility. 7. A conceptual model was presented to explain how climatic signals are filtered by the lake's exposure to climatic factors and by terrestrially mediated and in-lakc processes to reduce the coherence of lake pairs owing to time lags, frequency shifts and complex interference pattems. 8. Coherence is an important property to evaluate because it influences how broadly we can extrapolate results from a lake or set of lakes (for example, to a lake district) and because manipulative whole lake experiments often use adjacent lakes as reference lakes to evaluate treatment effects. The low coherence in this set of lakes in general and of individual variables such as chlorophyll concentrations and yellow perch year-class strength are discussed. 9. We found no studies that explicitly addressed interlake coherence; one long-term study of forest production made it clear that coherence among sites in a landscape will be a function of scale.     

The spatial distribution of desmids in lakes in northern Minnesota, U.S.A.

As a result of studies in certain lakes in northern Minnesota it has been found that the spatial distribution of desmids in them depends especially on the following factors: the constitution, abundance and distribution of the lakes' submerged aquatic flora and the morphometry and consequent patterns of their water circulation. The study has also shown a positive relationship between the size of desmid cells present in the plankton and the extent of water circulation. The latter factor may determine the composition and hence the diversity of lake phytoplankton.     

Applying remote sensing techniques to monitoring seasonal and interannual changes of aquatic vegetation in Taihu Lake,China

Knowledge of the composition and areal distribution of aquatic vegetation types, as well as their seasonal and interannual variations, is crucial for managing and maintaining the balance of lake ecosystems. In this study, a series of remotely sensed images with a resolution of 30 m (HJ-CCD and Landsat TM) were collected and used to map the distribution of aquatic vegetation types in Taihu Lake, China. Seasonal and interannual dynamics of aquatic vegetation types were explored and analyzed. The distribution areas of Type I (emergent, floating-leaved and floating vegetation) and Type II (submerged vegetation) were used to model their growing season phenology by double logistic functions. The resulting double logistic models showed, the area of Type I reached its peak in mid-August, and the maximum area for Type II occurred in mid-September. From 1984 to 2013, Type I area increased continuously from 59.75 km² to 148.00 km² (R² = 0.84), whereas the area covered by Type II first increased and then decreased, with a trend conforming to a significant quadratic curve (R² = 0.83). The eutrophication and stable state of Taihu Lake was assessed using a simple indicator which was expressed as a ratio of Type II area to Type I area. The results showed that the eutrophication in the lake might have been increasing in the area studied since 2000. Additionally, the results showed that air temperature had likely a direct effect on the growth of Type I (R² = 0.66) and a significant, but delayed, effect on the growth of Type II.     

Physical-chemical influences on vernal zooplankton community structure in small lakes and wetlands of Wisconsin,U.S.A.

We sampled zooplankton communities from 54 small water bodies distributed throughout Wisconsin to evaluate whether a snap-shot of zooplankton community structure during early spring could be used for the purpose of differentiating lakes from wetlands. We collected a single set of zooplankton and water chemistry data during a one-month time window (synchronized from south to north across the state) from an open water site in each basin as a means to minimize and standardize sampling effort and to minimize cascading effects arising from predator–prey interactions with resident and immigrant aquatic insect communities. We identified 53 taxa of zooplankton from 54 sites sampled across Wisconsin. There was an average of 6.83 taxa per site. The zooplankton species were distributed with a great deal of independence. We did not detect significant correlations between number of taxa and geographic region or waterbody size. There was a significant inverse correlation between number of taxa and the concentration of calcium ion, alkalinity and conductivity. One pair of taxa, Lynceus brachyurus and Chaoborus americanus, showed a significant difference in average duration of sites of their respective occurrence. All other pairs of taxa had no significant difference in average latitude, waterbody surface area, total phosphorus, total Kjeldahl nitrogen, alkalinity, conductivity, calcium ion, sulfate, nitrate, silicate or chloride. Taxa were distributed at random among the sites – there were no statistically significant pairs of taxa occurring together or avoiding each other. Multivariate analysis of zooplankton associations showed no evidence of distinct associations that could be used to distinguish lakes from wetlands. Zooplankton community structure appears to be a poor tool for distinguishing between lakes and wetlands, especially at the relatively large scale of Wisconsin (dimension of about 500 km). The data suggest that a small body of water in Wisconsin could be classified as a wetland if it persists in the spring and summer for only about 4 months, and if it is inhabited by Lynceus brachyurus, Eubranchipus bundyi, and if Chaoborus americanus and Chydorus brevilabris are absent.     

Phytoplankton as a factor in the decline of the submersed macrophyte Myriophyllum spicatum L. in Lake Wingra,Wisconsin, U.S.A.

A dramatic decline in biomass and areal coverage of the submersed macrophyte Myriophyllum spicatum in Lake Wingra, Wisconsin, USA during the mid-1970's is documented using aerial photography, vegetation surveys, and quadrat biomass sampling. Over the same period, light penetration as measured by Secchi disc transparency and extinction coefficient decreased substantially. During this period, extinction coefficient was closely correlated with chlorophyll a levels implicating phytoplankton as the major source of decreased light penetration. A growth model for M. spicatum predicts a substantial decline in macrophyte biomass when extinction coefficient is increased to the levels reported since 1977. Available data do not show whether the phytoplankton increase preceeded or followed the macrophyte decline. Nonetheless it is clear that phytoplankton growth can account for a substantial portion of the decline and that macrophyte recovery will be difficult given the phytoplankton-induced decrease in water clarity.     

Habitat level determinants of emergent macrophyte occurrence,extension and change in two large boreal lakes in Finland

Historical (1947–1950) and present day (1998–2000) aerial photograph data of aquatic vegetation were combined with soil, land use and habitat morphology variables in two lakes, oligotrophic L. Näsijärvi (256 km²) and eutrophic L. Pyhäjärvi (122 km²), with regulated water levels in southern Finland. Multivariate GLM analyses were used to examine the determining factors of occurrence and horizontal extension of vegetation, occurrence of common reed (Phragmites australis) and water horsetail (Equisetum fluviatile) and the vegetation change in 474 sites. Despite differences in geography and water level regulation between the lakes, congruent trends were identified. The vegetation occurrence in both lakes had a positive response to clay soils and incoming nutrients and a negative response to housing and shore slope. Moraine soils, housing and shore slope had a negative effect on horizontal extension of vegetation in both lakes. The occurrence of P. australis was controlled by a negative response to moraine and the occurrence of E. fluviatile to slope in both lakes. The vegetation change in both lakes was characterized by a negative response to housing and slope.     

Influence of stream geomorphic condition on fish communities in Vermont, U.S.A.

1. Evaluations of stream geomorphic condition may increase our understanding of the composite effects of human‐induced habitat change on fish communities. Using systematic sampling of 44 reaches spread across 26 rivers in Vermont from 2002 through 2004, we tested the hypothesis that stream reaches in reference geomorphic condition would support fish assemblages that differed in diversity and productivity from fish communities found in reaches of poorer geomorphic condition. 2. At each study reach, we sampled the fish community, identified the morphological unit according to common stream classification systems and then evaluated the extent of deviation from reference geomorphic condition using a regionally adapted geomorphic assessment methodology. 3. We used principal component analysis (PCA) and linear regression to build exploratory models linking stream geomorphic condition to fish community characteristics. 4. Our results suggest that geomorphic condition significantly influences fish community diversity, productivity and condition. Geomorphic condition was a significant factor in all of our fish community models. In conjunction with additional reach characteristics, geomorphic condition explained up to 31% of the total variance observed in models for species diversity of fish communities, 44% of the variance in assemblage biomass and 45% of the variance in a regional index of biotic integrity. 5. Our work builds on single‐species evidence that geomorphic characteristics represent important local‐scale fish‐habitat variables, showing that stream geomorphic condition is a dominant factor affecting entire fish communities. Our results enhance our understanding of the hierarchy of factors that influences fish community diversity and organisation and support the use of geomorphic condition assessments in stream management.     

A numerical analysis of the mesoscale distribution patterns of vascular plants in the subarctic Kevo Nature Reserve, northern Finland

Different numerical techniques were used to detect and describe the major ecological-biogeographical patterns of vascular plant distributions at the meso-scale level in a subarctic region in Finland. The distribution patterns of 231 native taxa in 362 1 km² grid squares of the Kevo Nature Reserve were analysed by two-way indicator species analysis and detrended correspondence analysis, and were subsequently related to twenty-eight geographical, topographical, geological, and vegetational variables using simple discriminant functions and canonical correspondence analysis with associated Monte Carlo permutation tests.
The floristic variation detected reflects variations in environmental factors operative at the regional and local scales. No major broad-scale coherent geographical patterns were detected; instead, the spatial distribution of the grids with a similar floristic composition shows a scattered distribution. All the numerical techniques reveal a major gradient from alpine areas to lowland sites with rivers and rocky outcrops, and the most important explanatory variables for predicting the main floristic variation are all associated with altitude. The floristic patterns represented by the second ordination gradient mainly correlate with the abundance of mires. Partial ordinations indicate that both the geographical and geological variables explain relatively little of the species distributional patterns.
Although the meso-scale approach reveals much about the plant-environment relationships in the study area, the floristic variation appears to be determined mainly by fine-scale factors. In the most heterogeneous grids, the grid size used fails to detect accurately the ecological patterns of the species present.     

A numerical analysis of arborescent communities in the rain forest of the Luquillo mountains,Puerto Rico

Summary Cluster analysis and canonical ordination were used as complementary techniques to identify major associations in a lower montane rain forest in Puerto Rico. These techniques were applied to forestry inventories from both secondary and primary communities. Eight major forest types were identified from the analyses and were confirmed by field checks. Distribution of these types was strongly correlated with past land-use and topographic position.Comprehensive ecological surveys are rare in moist tropical forests; however, forestry inventories are common and the results of this study suggest that valuable ecological information can be obtained from these data sets as well.Scientific Journal Series No. 10793 of the Minnesota Agricultural Experimental Station. Plant nomenclature according to Little & Wadworth (1964) and Little, Woodbury & Wadsworth (1974).This research was conducted while the senior author was stationed at the Institute of Tropical Forestry, USDA Forest Service, Rio Piedras, Puerto Rico.     

A comparison of the catchment sizes of rivers,streams, ponds,ditches and lakes: implications for protecting aquatic biodiversity in an agricultural landscape

In this study we compared the biodiversity of five waterbody types (ditches, lakes, ponds, rivers and streams) within an agricultural study area in lowland England to assess their relative contribution to the plant and macroinvertebrate species richness and rarity of the region. We used a Geographical Information System (GIS) to compare the catchment areas and landuse composition for each of these waterbody types to assess the feasibility of deintensifying land to levels identified in the literature as acceptable for aquatic biota. Ponds supported the highest number of species and had the highest index of species rarity across the study area. Catchment areas associated with the different waterbody types differed significantly, with rivers having the largest average catchment sizes and ponds the smallest. The important contribution made to regional aquatic biodiversity by small waterbodies and in particular ponds, combined with their characteristically small catchment areas, means that they are amongst the most valuable, and potentially amongst the easiest, of waterbody types to protect. Given the limited area of land that may be available for the protection of aquatic biodiversity in agricultural landscapes, the deintensification of such small catchments (which can be termed microcatchments) could be an important addition to the measures used to protect aquatic biodiversity, enabling ‘pockets’ of high aquatic biodiversity to occur within working agricultural landscapes. Guest editors: R. Céréghino, J. Biggs, B. Oertli & S. Declerck The ecology of European ponds: defining the characteristics of a neglected freshwater habitat     

Spatio-temporal dynamics of gastrointestinal helminths infecting four lake whitefish (Coregonus clupeaformis) stocks in northern lakes Michigan and Huron, U.S.A

This study was undertaken to identify the community composition, structure, and dynamics of helminths infecting the gastrointestinal tract (GIT) of lake whitefish (Coregonus clupeaformis) collected from 4 sites in northern lakes Huron (Cheboygan and De Tour Village) and Michigan (Big Bay de Noc and Naubinway) from fall 2003 through summer 2006. A total of 21,203 helminths was retrieved from the GITs of 1,284 lake whitefish. Approximately 42% (SE = 1.4%) of the examined lake whitefish were infected with at least 1 helminth species in their GIT, with a mean intensity of 39.4 worms/fish (SE = 0.3) and a mean abundance of 16.4 worms/fish (SE = 0.1). Collected helminths appeared to be generalists and consisted of 2 phyla (Acanthocephala and Cestoda) and 5 species (Acanthocephalus dirus, Neoechinorhynchus tumidus, Echinorhynchus salmonis, Cyathocephalus truncatus, and Bothriocephalus sp.). Lake whitefish from Lake Huron on average had greater infection prevalences, abundances, and intensities than did fish from Lake Michigan. Infection parameters for each of the helminth species generally followed the same pattern observed for the combined data. Acanthocephalus dirus was the most prevalent and abundant helminth in lake whitefish GITs, although intensity of infection was the greatest for C. truncatus. Helminth infection parameters often peaked in the spring while diversity was greatest in the winter samples. There was substantial temporal variability in helminth infections with prevalences, abundances, and intensities often fluctuating widely on consecutive sampling occasions. Analysis of the GIT helminth community composition suggested that 3 (Big Bay de Noc, De Tour Village, and Cheboygan) of the 4 primary spawning sites, overall, had similar community compositions. The reason for the observed spatial and temporal variability in the lake whitefish GIT helminth infections remains to be elucidated. The findings of this study represent the most comprehensive parasitological study ever conducted on lake whitefish in the Great Lakes and will provide valuable information for future comparisons.     

Relationship Between Avifaunal Occupancy and Riparian Vegetation in the Central Great Basin (Nevada, U.S.A.)

In western North America, riparian vegetation is being lost in response to changes in land use and climate. We examined the relationship between obligate riparian species of songbirds and environmental and riparian habitat factors in three mountain ranges in the central Great Basin (Nevada, U.S.A.). We estimated patterns of occupancy, colonization, and local extinction for three species detected during the breeding seasons of 2001–2006: MacGillivray's Warbler ( Oporornis tolmiei ), Broad-tailed Hummingbird ( Selasphorus platycercus ), and Song Sparrow ( Melospiza melodia ). We used model selection and multimodel inference to identify functional relationships between the occupancy of each species and multiple habitat variables, including the structure and composition of riparian vegetation. Among all years and species, we observed considerable variation in estimates of detection probability. For MacGillivray's Warbler, annual occupancy rates were relatively constant. Occupancy rates for Broad-tailed Hummingbird and Song Sparrow increased during the first 3–4 years of our study and then decreased. Each species experienced its highest rate of local extinction during 2005. Different components of riparian vegetation were good predictors of occupancy, colonization, and local extinction for each species. Typically, elevation and latitude also were strong predictors. Establishing functional relationships between avifauna and vegetation is essential to predicting how land-cover change may affect the occupancy of riparian areas and other habitats for birds. The conservation of breeding birds in riparian areas in the central Great Basin is more likely to succeed if the quality of their understory habitat as well as the canopy is maintained and restored.     

Aquatic vegetation and trophic condition of Cape Cod (Massachusetts,U.S.A.) kettle ponds

The species composition and relative abundance of aquatic macrophytes was evaluated in five Cape Cod, Massachusetts, freshwater kettle ponds, representing a range of trophic conditions from oligotrophic to eutrophic. At each pond, aquatic vegetation and environmental variables (slope, water depth, sediment bulk density, sediment grain size, sediment organic content and porewater inorganic nutrients) were measured along five transects extending perpendicular to the shoreline from the upland border into the pond. Based on a variety of multivariate methods, including Detrended Correspondence Analysis (DCA), an indirect gradient analysis technique, and Canonical Correspondence Analysis (CCA), a direct gradient approach, it was determined that the eutrophic Herring Pond was dominated by floating aquatic vegetation (Brasenia schreberi, Nymphoides cordata, Nymphaea odorata), and the algal stonewort, Nitella. Partial CCA suggested that high porewater PO₄-P concentrations and fine-grained sediments strongly influenced the vegetation of this eutrophic pond. In contrast, vegetation of the oligotrophic Duck Pond was sparse, contained no floating aquatics, and was dominated by emergent plants. Low porewater nutrients, low sediment organic content, high water clarity and low pH (4.8) best defined the environmental characteristics of this oligotrophic pond. Gull Pond, with inorganic nitrogen-enriched sediments, also exhibited a flora quite different from the oligotrophic Duck Pond. The species composition and relative abundance of aquatic macrophytes provide good indicators of the trophic status of freshwater ponds and should be incorporated into long-term monitoring programs aimed at detecting responses to anthropogenically-derived nutrient loading.     

Inter-annual patterns in macroinvertebrate communities of wilderness streams in Idaho, U.S.A.

This study examined the inter-annual variation in macroinvertebrate assemblages in six wilderness streams in central Idaho over a 6-year period (1990–1995). Benthic macroinvertebrates and associated environmental correlates were sampled during baseflow each summer. Little environmental change, as assessed using coefficients of variation (CVs) for substrate size and embeddedness, width, depth and periphyton standing crops, occurred in the streams over the period of study. There was also little temporal change in macroinvertebrate assemblages based on the relative abundance of the 10 most abundant taxa, all shredder taxa and all plecopteran taxa. CVs for individual taxa were substantially greater than those of most community measures, with rare taxa contributing 30–50% of the variation for any one stream. Frequency distributions for taxa CVs excluding rare taxa were more normally distributed. Differences in assemblage structure among streams were attributed to stream size (shift in shredder assemblages) and temperature (shift in plecopteran taxa). These data indicate a long-term (multi-year) persistence in the macroinvertebrate composition of these pristine streams, thus supporting the premise that such streams are excellent references for use in long-term biomonitoring programs.