Contrasting patterns in elevational diversity between microorganisms and macroorganisms

Aim Data and analyses of elevational gradients in diversity have been central to the development and evaluation of a range of general theories of biodiversity. Elevational diversity patterns have, however, been severely understudied for microbes, which often represent decomposer subsystems. Consequently, generalities in the patterns of elevational diversity across different trophic levels remain poorly understood. Our aim was to examine elevational gradients in the diversity of macroinvertebrates, diatoms and bacteria along a stony stream that covered a large elevational gradient. Location Laojun Mountain, Yunnan province, China. Methods The sampling scheme included 26 sites spaced at elevational intervals of 89 m from 1820 to 4050 m elevation along a stony stream. Macroinvertebrate and diatom richness were determined based on the morphology of the specimens. Taxonomic richness for bacteria was quantified using a molecular fingerprinting method. Over 50 environmental variables were measured at each site to quantify environmental variables that could correlate with the patterns of diversity. We used eigenvector‐based spatial filters with multiple regressions to account for spatial autocorrelation. Results The bacterial richness followed an unexpected monotonic increase with elevation. Diatoms decreased monotonically, and macroinvertebrate richness showed a clear unimodal pattern with elevation. The unimodal richness pattern for macroinvertebrates was best explained by the mid‐domain effect (r² = 0.72). The diatom richness was best explained by the variation in nutrient supply, and the increase in bacterial richness with elevation may be related to an increased carbon supply. Main conclusions We found contrasting patterns in elevational diversity among the three studied multi‐trophic groups comprising unicellular and multicellular aquatic taxa. We also found that there may be fundamental differences in the mechanisms underlying these species diversity patterns.     

Possible causes of high species diversity in tropical Australian freshwater macrobenthic communities

A total of 133 benthic macroinvertebrate species was recorded in four permanent freshwater lagoons (billabongs) and a stream riffle in the Magela Creek catchment, Northern Territory, Australia. 101 species were lentic in occurrence. Each billabong supported at least as many species as larger tropical and Australian temperate lakes, and was an exception to the species-poor status of Australian lentic macrobenthic communities. > 98% of the total benthic biomass was contributed by a mussel species; the remaining species' combined standing crop was an order of magnitude lower than in other lentic systems, further highlighting the diversity of the Magela benthos. Rarefaction (removal of organisms) and predictable environmental heterogeneity, both related to monsoonal variations in flow and water quality, were probably important determinants of the high diversity of these communities.     

The importance of worm identity and life history in determining the vertical distribution of tubificids (Oligochaeta) in a riverine mud

The vertical distribution of Tubifex tubifex, Limnodrilus hoffmeisteri and L. udekemianus, in a riverine mud was studied over a year. Distribution was dependent upon species identity, season and locality. The size structure of the population, and hence species life history, was of fundamental importance in determining temporal patterns of vertical distribution. A positive correlation between worm length and depth of penetration was clearly demonstrated for all three species. However, the mid-stream populations of the three species were closer to the mud surface during the summer and autumn than were the near-bank populations, although the size structures of the populations were not significantly different. Thus, another factor, possibly the distribution of food, also influenced the vertical distribution of the worms. Cocoon distribution was similar to that of the adult worms. Cocoons of the larger species, L. udekemianus, occurred deeper in the mud than those of T. tubifex. A comparison between the vertical distributions of tubificids in cores sectioned in situ, on the stream bank, and 30 mins later, showed there to be no significant change in distribution with time.     

Patches and the responses of lake benthos to sunfish nest-building

Summary Males of three sunfish species (Centrarchidae) construct nests for spawning and often share them sequentially in the littoral zone of a 4-hectare lake in New York State. To determine spatial and temporal effects of this reproductive behavior on zoobenthos in patches, I sampled bottom assemblages from inside nests and from adjacent (<1 m from nest perimeter), relatively undisturbed sites during the reproductive season of 1986 and immediately prior to nest-building in 1987. The reproductive behaviors of largemouth bass (Micropterus salmoides), redbreast sunfish (Lepomis auritus), and pumpkinseeds (L. gibbosus) altered relative abundances and significantly decreased benthic invertebrate diversity and density. These effects were extremely pronounced during the reproductive season and were partially detectable the following year. Community changes were probably the result of both bioturbation (modification of sediment size and organic content) and predation. The ecosystem-wide effects of nest-building are evaluated in terms of the number, distribution, and longevity of patches.     

青龙河底栖无脊椎动物群落结构及其水质评价

本文论述了青龙河底栖生物种类、数量、分布和结构等特点及其与环境因子间的关系。应用Beck、Gleason、Shannon、Simpson等生物指数对水质状况进行评价。结果表明青龙河除个别断面受污染外,大部分河段属尚清洁水。     

Factors influencing species diversity in saline waters of Death Valley,USA

Salinity is a major factor influencing the distributions and abundances of aquatic macroinvertebrates of saline waters in Death Valley, California, USA. A general pattern of declining numbers of species with increasing salinity is seen in Death Valley waters. Some species are restricted to low salinities, others are found only in highly saline pools, and still others are widely distributed over a broad range of salinities.Salinity alone cannot explain distributions seen in the field. Distributions and abundances of species such as the caddisfly Limnephilus assimilis Banks are broader than would be predicted on the basis of laboratory studies of salinity and temperature. I present evidence that for such species, biotic factors such as reduced predation at high salinities may compensate for increased physiological stress.     

Effects of the lampricide, 3-trifluoromethyl-4-nitrophenol (TFM) on the macroinvertebrates of a hardwater river

The effects of the lampricide, TFM, on the benthic macroinvertebrates in the Rouge River, a hardwater tributary to Lake Ontario was examined at 1 untreated and 2 treated sites over a 7 month period. Drift samples were collected from one one of the treated sites during the 5 days bracketing treatment. Significant decreases in relative abundance attributable to TFM were recorded for Chimarra sp., Dugesia sp. and Tubificoidea 2–19 d following treatment. Large reductions were also exhibited by Caenis sp. and Lumbricidae. Two-thirds of the Chironomidae genera and Nematoda tended to decline in abundance 2 d after treatment at only one of the treated sites, probably due to a 2.5 h longer treatment. This decline was followed by a significant increase to greater than pretreatment abundances 17 d later undoubtedly as a result of an upward migration of macroinvertebrates from within the hyporheos. Partial recolonization of the TFM-sensitive benthic taxa was evident 19 d after lampricide treatment with complete recolonization 6.5 months later. With the exception of Caenis sp. those taxa in the present study found to be TFM-sensitive were in accordance with those found in softwater field studies. Chimarra sp., Dugesia sp., Hemerodromia sp., Lumbricidae and Tubificoidea exhibited substantial increases in drift abundance resulting from TFM treatment. Generally drift abundance of the taxa returned to pretreatment levels within 12 h following the completion of treatment. The drift abundance of Chimarra sp. and Dugesia sp. remained above normal throughout the rest of the sampling period likely due to continued irritation or mortalities induced by the presence of TFM in the substrate. Generally, drift was a good indicator of those taxa likely to experience a decline in abundance as a result of TFM treatment.     

Distribution of macroinvertebrates in the shallow part of ‘De Gijster’, a water storage lake in the Biesbosch (The Netherlands)

The composition and distribution of the macroinvertebrate fauna of the shallow part of De Gijster, a medium sized water storage lake in The Netherlands, has been studied during 1984. The numerous individuals collected belong mainly to the Oligochaeta, Diptera (Chironomidae larvae) and Mollusca. Amongst them are elements of both the former polder fauna and the river fauna. A quantitative analysis revealed data on the horizontal distribution of several taxa within the lake as well as data on the influence of the lifecycle of some taxa on the annual composition of the fauna.     

The response of stream macroinvertebrates to substrate size and heterogeneity

Manipulations of substrate size and components of heterogeneity were designed to test their independent effects and interactions on the abundance and species richness of stream macroinvertebrates. Two components of substrate heterogeneity, variation in size class proportions and number of size classes, had no independent effect on abundance or richness; and in general did not interact with median particle size. Median particle size, stream current, and detritus accounted for most of the significant variation in macroinvertebrates colonizing the experimental substrates. Rocks with high surface heterogeneity (roughness) were colonized by more individuals (but not taxa) than rocks with low surface heterogeneity.     

Redescription of Vorticella oceanica Zacharias, 1906 (Ciliophora: Peritrichia) with notes on its host, the marine planktonic diatom Chaetoceros coarctatum Lauder,1864

The late-spring quantitative relationship between epiphyton and macroinvertebrates was analyzed on the basis of units of colonizable plant surface of Typha angustifolia, Phragmites australis and Nuphar lutea (floating leaves) in the shallow euthrophic Lake Loosdrecht (the Netherlands), with a high seston load. The non-predatory chironomid larvae (Glyptotendipes viridis, Endochironomus albipennis, Pentapedilum sordens, Cricotopus sylvestris agg.) dominated among the macroinvertebrate taxa, controlling the diversity and resemblance of macroinvertebrate assemblages. There was a gradient in functional feeding groups among the chironomids from continuous filtering of the seston to prevailing utilization of epiphyton. We found no direct relationship between the total macroinvertebrate abundance and the epiphyton mass on the plants surface. We attribute this to the filter feeding-strategy of the most abundant species, Glyptotendipes viridis, that utilizes seston in the eutrophicated lake.