Response of the waterbird community to floating pennywort (Hydrocotyle ranunculoides) cover at Ngamo dam,Antelope Park,Zimbabwe.

Little is known on the influence of invasive aquatic weeds on afro‐tropical waterbird communities. We used bird counts in sites of varying floating pennywort Hydrocotyle ranunculoides cover to explore the relationship between the weed and the waterbird community dynamics at Ngamo dam, Antelope Park, Zimbabwe. Waterbird communities in low‐to‐medium weed cover sites were more diverse and abundant compared to sites of high weed cover. In addition to supporting birds such as African Jacana which are able to forage within dense aquatic plants, high weed cover sites were associated with birds whose diets include invertebrates and fish which are likely more abundant and diverse in these sites. In contrast, low‐to‐medium weed cover sites were associated with bird species such as Common Moorhen, Great Egret, Pied Kingfisher and African Fish Eagle which require accessible open water and forage for diving, swimming or wading. The increased bird abundance in low‐to‐medium weed cover sites also likely increases prey for predatory birds. Thus, the negative changes in the waterbird community composition, abundance and diversity in response to increasing floating pennywort cover reflects species‐specific tolerances to floating pennywort and its influence on accessible open water, foraging sites and prey availability.     

Arctic arthropod assemblages in habitats of differing shrub dominance

Recent climate warming in the Arctic has caused advancement in the timing of snowmelt and expansion of shrubs into open tundra. Such an altered climate may directly and indirectly (via effects on vegetation) affect arctic arthropod abundance, diversity and assemblage taxonomic composition. To allow better predictions about how climate changes may affect these organisms, we compared arthropod assemblages between open and shrub‐dominated tundra at three field sites in northern Alaska that encompass a range of shrub communities. Over ten weeks of sampling in 2011, pitfall traps captured significantly more arthropods in shrub plots than open tundra plots at two of the three sites. Furthermore, taxonomic richness and diversity were significantly greater in shrub plots than open tundra plots, although this pattern was site‐specific as well. Patterns of abundance within the five most abundant arthropod orders differed, with spiders (Order: Araneae) more abundant in open tundra habitats and true bugs (Order: Hemiptera), flies (Order: Diptera), and wasps and bees (Order: Hymenoptera) more abundant in shrub‐dominated habitats. Few strong relationships were found between vegetation and environmental variables and arthropod abundance; however, lichen cover seemed to be important for the overall abundance of arthropods. Some arthropod orders showed significant relationships with other vegetation variables, including maximum shrub height (Coleoptera) and foliar canopy cover (Diptera). As climate warming continues over the coming decades, and with further shrub expansion likely to occur, changes in arthropod abundance, richness, and diversity associated with shrub‐dominated habitat may have important ecological effects on arctic food webs since arthropods play important ecological roles in the tundra, including in decomposition and trophic interactions.     

Structure of biological soil crust communities in Callitris glaucophylla woodlands of New South Wales,Australia

Question: What is the nature of the relationships between cover, diversity and abundance of biological soil crusts, cover and diversity of vascular plants, and annual rainfall, soil texture and forestry practices in Callitris glaucophylla woodlands? Location: Arid and semi‐arid Callitris glaucophylla‐domi‐nated woodlands of eastern Australia. Methods: We documented soil crust‐forming mosses, lichens and liverworts at 83 woodland sites along a gradient of declining rainfall. Linear and non‐linear regression were used to examine relationships between soil crust species and attributes of vascular plant communities, and a similarity matrix (species abundance X sites) was subjected to Non‐metric Multi‐Dimensional Scaling (MDS), and Analysis of Similarities (ANOSIM) to show the degree of association between groups of taxa, and soil texture, rainfall classes and forestry practices. Results : We collected 86 taxa. Mosses were dominated by the family Pottiaceae, and lichens were dominated by squamulose forms. Average annual rainfall was highly correlated with soil crust community composition, and loamy soils supported a greater cover and diversity of taxa compared with sandy soils. Increases in tree cover were associated with significant, though weak, increases in abundance, but not diversity, of crusts. Crusts tended to be more diverse in areas that (1) had a sparse cover of ground‐storey plants; (2) were relatively stable ‐ as indicated by the proportion of perennial and/or native plants; (3) had more stable soil surfaces; and (4) were unlogged. Litter cover, overstorey thinning, and livestock grazing had no appreciable effect on crust diversity or cover. Conclusions : Callitris glaucophylla woodlands provide substantial habitat for soil crust organisms, and the dense tree cover and closed canopies of Callitris do not appear to have a major influence on the structure of biological crust communities. Unlike other woodland systems, relatively few patches would be required to reserve a high diversity of crust species.     

Testate amoebae taxonomy and trait diversity are coupled along an openness and wetness gradient in pine-dominated Baltic bogs

Sphagnum peatlands host a high abundance of protists, especially testate amoebae. Here, we designed a study to investigate the functional diversity of testate amoebae in relation to wetness and forest cover in Baltic bogs. We provided new data on the influence of openness/wetness gradient on testate amoebae communities, showing significant differences in selected testate amoebae (TA) traits. Three key messages emerged from our investigations: 1) we recorded an effect of peatland surface openness on testate amoebae functional traits that led us to accept the hypothesis that TA traits differ according to light intensity and hydrology. Mixotrophic species were recorded in high relative abundance in open plots, whereas they were nearly absent in forested sites; 2) we revealed a hydrological threshold for the occurrence of mixotrophic testate amoebae that might be very important in terms of peatland functioning and carbon sink vs. source context; and 3) mixotrophic species with organic tests were nearly absent in forested sites that were dominated by heterotrophic species with agglutinated or idiosomic tests. An important message from this study is that taxonomy of TA rather indicates the hydrological gradient whereas traits of mixotrophs the openness gradient.     

Passive recovery of small vertebrates following livestock removal in the Australian rangelands

In arid environments, grazing by exotic herbivores, including domestic livestock, can greatly influence native, small vertebrate assemblages. Whether the removal of livestock facilitates passive recovery of these assemblages depends on habitat condition and the species present. We explore changes in small mammal and reptile species richness, abundance, and composition in a degraded chenopod shrubland dominated by Acacia victoriae ssp. and open Acacia aneura (mulga) woodland destocked in 1976 and 1984, respectively. Data were obtained between 1997 and 2007, from two grazed and two ungrazed sites in each community. Species richness increased at a faster rate in ungrazed open A. aneura woodland, but did not differ significantly between ungrazed and grazed degraded chenopod shrubland. Subsequent analyses at a finer‐scale detected disparate responses in richness and abundance for microhabitat. At this scale, a greater number of species‐specific responses were also detected, including increased abundance of generalist species and decreased abundance of species requiring low cover. These results reiterate the potential for species‐specific responses to livestock that are more apparent in particular microhabitats. Furthermore, this investigation provides evidence for the gradual passive recovery of small mammal and reptile assemblages in both communities, which is facilitated by the removal of livestock in open A. aneura woodland in fair condition, but not degraded chenopod shrubland in poor condition.     

The influence of chemistry and habitat features on the microcrustacea of some upland Welsh streams

SUMMARY. 1. Microcrustaceans were sampled during September 1990 from three microhabitats (margins, stony riffles and gravel) at thirteen stream sites in mid-Wales.
2. Patterns in the distribution, abundance and community structure of microcrustacean taxa were related to stream chemistry, physiography, substratum composition and marginal habitat structure. Patterns of distribution between microhabitats were also assessed.
3. Chemical variables were the strongest correlates with microcrustacean parameters. Total numbers of microcrustaceans and harpacticoid copepods were reduced at sites with high aluminium concentrations, and ostracods were scarce or absent at the most acidic sites. In contrast, cyclopoid copepods were more abundant and species rich at low pH.
4. Microcrustacean communities were most species rich at sites with a high percentage cover of macrophytes on the substratum. Cladoceran species richness and abundance, and the abundance of several microcrustacean species, were also positively correlated with percentage macrophyte cover.
5. Three site groupings produced by TWINSPAN classification were primarily related to percentage macrophyte cover and marginal habitat structure, with chemistry and land use also of importance.
6. Total microcrustacean abundance was highest in margins, but of all the species, only the harpacticoid Bryocamptus cuspidatus showed a strong microhabitat preference.     

Changes in soil macroarthropod communities in relation to forest maturation through three successional stages in the Canadian boreal forest

The edaphic macroarthropod communities of three sites representative of the forest succession in the Lake Duparquet region (situated in the southern part of the boreal forest, Abitibi, Quebec, Canada) were studied. A 47-year-old deciduous forest, a 144-year-old mixed forest, and a 231-year-old coniferous forest form a successional forest gradient with a vegetation composition that is a function of the time elapsed since the last forest fire. Along with forest succession, there is a reduction in macroarthropod community biodiversity. There is a negative gradient for mean total abundance (237–41 individuals), total richness (63–23 species), density (1792–661 individuals/m²), diversity (H′ = 1.478–1.007) and equitability (J = 0.821–0.739). These community changes affect saprophagous organisms more than predators. Certain species or taxa show preferences for a particular forest type, such as larval Diptera for the deciduous forest. A comparison of these results with the literature suggests an inverse preference as to habitat choice between microarthropods (Acarina and Collembola) and macroarthropods. From a conservation point of view, macroarthropod biodiversity will be favored by the protection of all forest types since each environment possesses a particular community structure and species. Received: 17 April 1995 / Accepted: 1 April 1996     

Patterns of Species Number and Abundance in Macroalgal Communities in Coastal Waters

Predictable patterns of species number have been observed in relation to habitat size, habitat heterogeneity and environmental conditions, while patterns in relative abundance of species have been examined for few communities and no assembly rules have been established. We studied communities of attached macroalgae in 61 individual sites located in four different areas; the inner, middle and outer parts of three neighbouring low-tidal estuaries and the adjacent open waters of the Kattegat, Denmark. The objectives were to determine (1) the relationships of species number and rank-abundance to the environmental conditions, and (2) the importance of scale and the consistency of species rank number at the sites for these relationships. We found that species number increased significantly from the inner estuaries to the open coastal waters along with decreasing nutrient concentrations. Turnover (β) diversity was lowest in the open waters suggesting that species composition was more similar among samples there than in the estuaries. Rank-abundance curves did not differ between depth intervals and individual sites across the environmental gradients. However, the summed rank-abundance patterns for two sites showed significantly steeper initial slopes and dominance of few species (i.e., low evenness) in the inner estuaries than in open waters. This pattern was due to high rank consistency of dominant species among sites in the inner estuaries. In open waters rank consistency was low, and the summed abundance across sites showed an even abundance of species. The results imply that the scale of the study and the community variability observed at that particular scale, is the main determinant of abundance patterns.     

Effects of cover soil stockpiling on plant community development following reclamation of oil sands sites in Alberta

Stockpiling of cover soil can influence vegetation development following reclamation. Cover soil, comprising the upper 15–30 cm of the surface material on sites scheduled for mining, is commonly salvaged prior to mining and used directly or stockpiled for various lengths of time until it is needed. Salvaging and stockpiling causes physical, chemical, and biological changes in cover soils. In particular, stockpiling reduces the availability and vigor of vegetative propagules and seed, and can lead to increases in the abundance of some weedy species. This study uses data from monitoring plots to assess how stockpiling of cover soil impacts plant community development on reclaimed oil sands mine sites in northern Alberta. Development of plant communities differed distinctly between directly placed and stockpiled cover soil treatments even 18 years after reclamation. Direct placement of cover soil resulted in higher percent cover, species richness, and diversity. Nonmetric multidimensional scaling and multiresponse permutation procedure revealed compositional differentiation between the treatments. Indicator species analysis showed that direct placement treatment was dominated by perennial species while grasses and annual forb species dominated sites where stockpiled soil was used. Results indicate that stockpiling leads to slower vegetation recovery while direct placement of cover soil supports more rapid succession (from ruderal and annual communities to perennial communities). In addition, direct placement may be less costly than stockpiling. However, scheduling of salvage and placement remains a challenge.     

Fish and Phytoplankton Exhibit Contrasting Temporal Species Abundance Patterns in a Dynamic North Temperate Lake

Temporal patterns of species abundance, although less well-studied than spatial patterns, provide valuable insight to the processes governing community assembly. We compared temporal abundance distributions of two communities, phytoplankton and fish, in a north temperate lake. We used both 17 years of observed relative abundance data as well as resampled data from Monte Carlo simulations to account for the possible effects of non-detection of rare species. Similar to what has been found in other communities, phytoplankton and fish species that appeared more frequently were generally more abundant than rare species. However, neither community exhibited two distinct groups of “core” (common occurrence and high abundance) and “occasional” (rare occurrence and low abundance) species. Both observed and resampled data show that the phytoplankton community was dominated by occasional species appearing in only one year that exhibited large variation in their abundances, while the fish community was dominated by core species occurring in all 17 years at high abundances. We hypothesize that the life-history traits that enable phytoplankton to persist in highly dynamic environments may result in communities dominated by occasional species capable of reaching high abundances when conditions allow. Conversely, longer turnover times and broad environmental tolerances of fish may result in communities dominated by core species structured primarily by competitive interactions.     

Birds,Cattle, and Bracken Ferns: Bird Community Responses to a Neotropical Landscape Shaped by Cattle Grazing Activities

Large areas of tropical moist forests have been converted to cattle pastures, generating complex landscapes where different habitats are represented by small patches with an uneven spatial distribution. Here, we describe how bird communities respond to the different elements present in a livestock landscape that was originally dominated by tropical moist forest. We surveyed six habitats: open pastures, pastures with shrubs, early‐ and middle‐secondary forests, mature forest, and pastures invaded by bracken ferns (Pteridium aquilinum). Bird diversity was high in secondary and mature forests, and low in fern‐invaded sites and open pastures. Fern‐dominated sites had the lowest bird species richness, and trophic guild diversity of all habitats. Habitat structure affected both bird species richness and densities in similar ways. Tree species richness was the habitat attribute that had a bigger positive effect on bird species richness. Bird community structure varied among sampled habitats, separating habitats in two major groups (forests and pastures). Our data indicate that bracken fern‐invaded pastures were the worst habitat condition for avian communities. To increase bird diversity, we recommend to eliminate or manage bracken fern and to increase shrub and tree cover in open pastures to provide food resources and shelter for birds. Finally, we encourage the maintenance of secondary and mature forest remnants as a strategy to conserve resident birds within a landscape dominated by livestock activities.     

Community structure of the epipelagic zooplankton community under the sea-ice of the northern Weddell Sea

Summary The present paper describes the composition, abundance, biomass and diversity of the meso- and macrozooplankton in the epipelagic zone of the open water and under the ice of the northern Weddell Sea. Samples were collected in October/November 1988 with a multiple RMT1+8 net during the European Polarstern Study (EPOS). Multivariate analysis resulted in two distinct site clusters, a northern one mainly located in the open water/marginal ice zone and a southern one extending from the marginal ice zone into the consolidated pack-ice. Clusters were, however, faunistically coherent with a high degree in positive covariation of species. There was no basis for the separation into communities, but differences occurred on the population level in numerical abundances, biomass (wet weight) and in a shift in species dominance. Different ice zones and vertical layers were tested among each other with regard to their relative species abundance. Significant differences were found between the upper 60 m layer of the open sea, the upper 60 m layer of the closed pack-ice and the so called transitional zone. Species richness and diversity was lowest directly under the closed pack-ice. Abundance and biomass was highest in the surface layer of the open water, while both variablès decreased dramatically under the ice. Copepods dominated numerically in open water, while salps dominated in biomass. Euphausia superba and Thysanoessa macrura were the dominant species in the upper water column of the closed pack-ice zone. Krill was the only species with increasing abundance in the sub-ice area and a dominance in biomass of more than 91% demonstrated its unique importance for the sub-ice habitat.Data presented here were collected during the European Polarstern Study (EPOS) sponsored by the European Science Foundation     

Interaction between disturbance and primary productivity in determining stream invertebrate diversity

Invertebrate diversity patterns were examined in 10 streams that differed in substrate disturbance rates, in Taranaki, New Zealand, between April 1999 and January 2000. Two sites on each stream were sampled, one under native forest canopy where light was postulated to limit periphyton growth and a similar site 225–3800 m downstream in open grassland. Periphyton biomass was considerably higher at open stable sites than at closed or unstable sites. Associated with the higher algal biomass, species number and total abundance of animals were higher at open canopy sites. Species number exhibited a negative linear relationship with disturbance but only at open sites. In contrast, rarefied species richness exhibited a negative linear relationship with disturbance at both open and closed sites. This was a result of communities at the more disturbed sites being numerically dominated by only a few taxa compared to the more evenly distributed communities at stable sites. The observed patterns provide little support for contemporary diversity disturbance models but suggest diversity of invertebrates in streams is a function of time since the last disturbance, mediated through recovery of the food base in autotrophic streams.     

Community structure of pollination webs of Mauritian heathland habitats

Pollination webs have recently deepened our understanding of complex ecosystem functions and the susceptibility of biotic networks to anthropogenic disturbances. Extensive mutualistic networks from tropical species-rich communities, however, are extremely scarce. We present fully quantitative pollination webs of two plant–pollinator communities of natural heathland sites, one of which was in the process of being restored, on the oceanic island of Mauritius. The web interaction data cover a full flowering season from September 2003 to March 2004 and include all flowering plant and their pollinator species. Pollination webs at both sites were dominated by a few super-abundant, disproportionately well-connected species, and many rare and specialised species. The webs differed greatly in size, reflecting higher plant and pollinator species richness and abundance at the restored site. About one fifth of plant species at the smaller community received <3 visits. The main pollinators were insects from diverse taxonomic groups, while the few vertebrate pollinator species were abundant and highly linked. The difference in plant community composition between sites appeared to strongly affect the associated pollinator community and interactions with native plant species. Low visitation rate to introduced plant species suggested little indirect competition for pollinators with native plant species. Overall, our results indicated that the community structure was highly complex in comparison to temperate heathland communities. We discuss the observed differences in plant linkage and pollinator diversity and abundance between the sites with respect to habitat restoration management and its influence on pollination web structure and complexity. For habitat restoration to be successful in the long term, practitioners should aim to maintain structural diversity to support a species-rich and abundant pollinator assemblage which ensures native plant reproduction.     

The control of the development of a marine benthic community by predation on recruits

Recruitment is an important process in regulating many marine benthic communities and many studies have examined factors controlling the dispersal and distribution of larval immigrants. However, benthic species also have early post-settlement life-stages that are dramatically different from adult and larval stages. Predation on these stages potentially impacts measured recruitment and the benthic populations and communities that ultimately develop.We examined the consequences of post-settlement predation on 1-day-old to 1-month-old recruits of sessile invertebrates at two field sites in southern New England. One site (Breakwater) was in a protected area with few predators and the other (Pine Island) was <1 km away in an open coast area with three different predator guilds: small and large invertebrates and fish. The Breakwater site had been dominated for >10 years by colonial and solitary ascidians. These species were absent from the Pine Island site which was dominated by bryozoans. Our goal was to examine whether post-settlement predation influenced the development and subsequent structure of the epifaunal community.Here we examine long-term changes in community development resulting from post-settlement predation, and contrast these results to those of earlier experiments examining the reductions in observed recruitment by post-settlement predation. Our first long-term experiment examined natural community development at the two sites and whether transplanted communities changed when exposed to the different levels of predation at these sites. The communities that developed at both sites were consistently different from each other and similar to resident communities at their respective sites. On panels transplanted from the Breakwater to Pine Island, solitary ascidians and the colonial ascidian, Botryllus schlosseri, suffered high mortalities on both caged and uncaged treatments, indicative of predation by small predators that could enter cages. Some solitary ascidians did survive inside cages and the colonial ascidian, Botrylloides violaceus, became dominant on all transplanted treatments. On panels transplanted from Pine Island to the Breakwater, ascidians invaded and dominated all treatments except those that were originally caged at Pine Island.In the second long-term experiment, natural communities were allowed to develop on panels exposed at the Breakwater for 1, 2, 3, and 4 weeks. Each set was transplanted to three treatments at Pine Island: open uncaged pilings, caged pilings to exclude fish and large invertebrates, and racks suspended above the bottom to exclude all predators. When 1-week-old communities were transplanted, after 2-3 weeks only bryozoans were found on the open and caged pilings, while colonial ascidians dominated the suspended rack treatment. When older 2-week-old communities were transplanted, colonial ascidians also became dominant in the caged piling treatment and when 3- and 4-week-old communities were transplanted colonial ascidians dominated all three treatments. Solitary ascidians were never abundant on open pilings exposed to fish and large benthic invertebrate predators.Post-settlement predator-prey interactions involved newly settled and juvenile life-stages of a variety of prey species and many invertebrate and vertebrate predator species. The effects of these interactions on recruitment did result in differences in the development and eventual species composition of the communities, even though predators had little if any effect on the adults of the prey species.     

Short-term climatic trends affect the temporal variability of macroinvertebrates in California 'Mediterranean' streams

1. Long‐term studies in ecology are essential for understanding natural variability and in interpreting responses to disturbances and human perturbations. We assessed the long‐term variability, stability and persistence of macroinvertebrate communities by analysing data from three regions in northern California with a mediterranean‐climate. During the study period, precipitation either increased or decreased, and extreme drought events occurred in each region. 2. Temporal trends in precipitation resulted in shifts from ‘dry‐year’ communities, dominated by taxa adapted to no or low flow, to ‘wet‐year’ communities dominated by taxa adapted to high flows. The abundance of chironomid larvae was an important driver of community change. Directional change in community composition occurred at all sites and was correlated with precipitation patterns, with more dramatic change occurring in smaller streams. 3. All communities exhibited high to moderate persistence (defined by the presence/absence of a species) and moderate to low stability (defined by changes in abundance) over the study period. Stability and persistence were correlated with climatic variation (precipitation and El Niño Southern Oscillation) and stream size. Stability and persistence increased as a result of drought in small streams (first‐order) but decreased in larger streams (second‐ and third‐order). Communities from the dry season were less stable than those from the wet‐season. 4. This study demonstrates the importance of long‐term studies in capturing the effects of and recovery from rare events, such as the prolonged and extreme droughts considered here.     

Stratification and dynamics of microbial loop communities in Lake Fryxell, Antarctica

1. Lake Fryxell, situated in the McMurdo Dry Valleys, Antarctica, offers the opportunity to study microbial loop processes in the absence of crustacean zooplankton and other higher organisms. This is the first study of Lake Fryxell to provide detailed temporal and vertical variations of microbial loop organisms.
2. Protozoan communities are concentrated around the chemocline (9–10 m) in Lake Fryxell. Phototrophic nanoflagellates (PNAN), heterotrophic nanoflagellates (HNAN) and ciliates formed deep maxima of 14 580, 694 and 58 cells mL−1 respectively. Although abundance and biomass at the chemocline was high, diversity of protozoa was low, Plagiocampa accounting for> 80% of the total ciliate biomass.
3. In the mixolimnion (4.5–8 m), protozoa were less abundant, but more diverse, with 24 ciliate morphotypes being identified within this region of the water column. Inter-annual variability of protozoan biomass and abundance was greater in the mixolimnion than at the chemocline due to more variable nutrient and prey concentrations.
4. Physicochemical gradients in Lake Fryxell were very stable because the perennial ice cover reduced wind driven currents. As a consequence, ciliate species occurred in distinct depth strata, Monodinium being most abundant directly beneath the ice cover, Askenasia having maximum abundance at 8 m and Plagiocampa dominating ciliate biomass at the chemocline. The lack of vertical mixing reduced seasonal successions of PNAN and ciliate species. Three cryptophyte species dominated the PNAN community at all times (>79% of total biomass).     

Conversion of sagebrush shrublands to exotic annual grasslands negatively impacts small mammal communities

Aim The exotic annual cheatgrass (Bromus tectorum) is fast replacing sagebrush (Artemisia tridentata) communities throughout the Great Basin Desert and nearby regions in the Western United States, impacting native plant communities and altering fire regimes, which contributes to the long‐term persistence of this weedy species. The effect of this conversion on native faunal communities remains largely unexamined. We assess the impact of conversion from native perennial to exotic annual plant communities on desert rodent communities. Location Wyoming big sagebrush shrublands and nearby sites previously converted to cheatgrass‐dominated annual grasslands in the Great Basin Desert, Utah, USA. Methods At two sites in Tooele County, Utah, USA, we investigated with Sherman live trapping whether intact sagebrush vegetation and nearby converted Bromus tectorum‐dominated vegetation differed in rodent abundance, diversity and community composition. Results Rodent abundance and species richness were considerably greater in sagebrush plots than in cheatgrass‐dominated plots. Nine species were captured in sagebrush plots; five of these were also trapped in cheatgrass plots, all at lower abundances than in the sagebrush. In contrast, cheatgrass‐dominated plots had no species that were not found in sagebrush. In addition, the site that had been converted to cheatgrass longer had lower abundances of rodents than the site more recently converted to cheatgrass‐dominated plots. Despite large differences in abundances and species richness, Simpson’s D diversity and Shannon‐Wiener diversity and Brillouin evenness indices did not differ between sagebrush and cheatgrass‐dominated plots. Main conclusions This survey of rodent communities in native sagebrush and in converted cheatgrass‐dominated vegetation suggests that the abundances and community composition of rodents may be shifting, potentially at the larger spatial scale of the entire Great Basin, where cheatgrass continues to invade and dominate more landscape at a rapid rate.     

First survey of sessile communities on subtidal rocks in an area with hydrothermal vents: Milos Island,Aegean Sea

The major epibenthic communities on subtidal rocks of Palaeochori Bay and the marine tract on the southern coast of Milos Island (Greece) were described down to 44 m depth. Six sites were investigated by snorkelling and SCUBA diving. Samples, photographs and video images were also taken to integrate information. Three out of the six sites were close to hydrothermal vents, a common feature in the area. In total, nine major epibenthic communities were found, most of which were characterised by a diverse algal growth down to the maximum depth explored. Macrobenthic cover was severely reduced only in the close proximity of vents, a white flocculent bacterial mat covering the rock at the point from which fluid escaped. Large-scale effects of vents on the epibenthic communities were not detected. However, the abundance of species with warm-water affinity was recognisable in both algal and animal dominated communities, which may be related to higher winter temperature in the vent area. Epifaunal communities under overhangs were composed of distinct groups of suspension feeders at vent as compared to non-vent sites: this might indicate differences in trophic conditions. Mounds of the bioconstructional coralline alga Mesophyllum lichenoides were conspicuous only at vent sites, thus suggesting enhanced biodeposition of carbonates due to vent activity.