Biodiversity in agricultural landscapes: the ground beetle communities of woody uncultivated habitats

Agricultural landscapes can be defined as mosaics of landscape elements which are affected by farming practices. Woodland habitats, even though they are managed, are amongst the most stable elements of agricultural landscapes and can play a key role in the maintenance of biodiversity. This study of the ground beetle (carabid) communities of woodlands and woody linear features in a Scottish agricultural landscape shows that these habitats contribute significantly to the overall landscape diversity of these beetles. Communities in woods and hedgerows display the same species diversity and are both characterized by the presence of forest species. The main factors constraining carabid communities in both environments are the grazing intensity and, to a lesser extent, the type of soil. Heavily grazed locations are characterized by the occurrence of grassland species while forest species are restricted to ungrazed locations. At the landscape scale, the distribution of the forest species is limited by spatial isolation, indicating that there are insufficient functional links between woodland habitats in the study area. Isolation could be compensated for either by a better control of grazing so that linear features can be used as dispersal corridors for forest carabids or by planting more linear features and woods in the area.     

Species and functional trait re-assembly of ground beetle communities in restored grasslands

Ecosystem restoration provides unique opportunities to study community dynamics under succession and can reveal how consumer communities re-assemble and respond to successional changes. Studying community dynamics from both taxonomic and functional trait perspectives also may provide more robust assessments of restoration progress or success and allow cross-system comparisons. We studied ground beetle (Coleoptera: Carabidae) communities for three years in a restored grassland chronosequence with sites from 0 to 28 years old. We measured traditional community metrics (abundance, richness, Shannon diversity) and functional trait metrics based on species’ body length, wing morphology, activity time, phenology, and diet. Communities had high species richness and abundance in early successional stages, but these declined in later stages to low levels comparable to an adjacent grassland remnant. Species composition also shifted with time, converging with the remnant. Although functional richness, like species richness, declined as succession progressed, functional divergence quickly increased and was maintained over time, suggesting niche differentiation in established communities. Young sites were typified by small, macropterous, phytophagous species, while older sites contained larger species more likely to be flightless and carnivorous. Prescribed burns also affected traits, decreasing prevalence of larger species. This study demonstrates that functionally diverse consumer communities can self-assemble under restoration practices. In a relatively short amount of time both morphological and trophic level diversity are established. However, prescribed fire intended to control non-desirable plants may also shape beetle community functional composition, and restoration managers should consider if plant community benefits of fire outweigh potential declines in consumer function.     

Using stone cover patches and grazing exclusion to restore ground-active beetle communities in a degraded pseudo-steppe

The dry grasslands of La Crau, a pseudo-steppe ecosystem located in Southern France, have experienced drastic reduction and degradation due to intensive agricultural activities for the past 50 years, leading to changes in their beetle assemblage. This valuable ecosystem is characterized by 50% stone cover, consisting of remnants from an old riverbed, and centuries-old sheep grazing. However, much of the stone cover has been removed for the purposes of cultivation. With the aim of restoring this ecosystem, we manipulated these two principal ecological factors: sheep grazing (grazing/exclusion) and stone cover (50% stone cover/no large stones). This study was conducted on a former cultivated field and on a pseudo-steppe area. On each of the two areas, 12 experimental units contained four different treatment patches: (1) stones × grazing, (2) no stones × grazing, (3) no stones × no grazing and (4) stones × no grazing, were randomly positioned. Data were obtained from 96 pitfall traps (one on each patch). After 4 years, restored stone cover combined with grazing exclusion significantly improved beetle abundance and increased beetle richness (38 species vs. 22 in the grazed-no-stones treatment), whereas no significant differences were recorded in the three other treatments. Our results therefore suggest that removing grazing for a few years and restoring stone cover is a promising method to restore beetle assemblages in this type of ecosystem.     

Response of copronecrophagous beetle communities to habitat disturbance in two mountains of the Mexican Transition Zone: influence of historical and ecological factors

We analyze the influence of historical and ecological factors on the diversity and composition of communities of copronecrophagous beetles associated with conserved and disturbed habitats on two mountains of the Mexican Transition Zone: one mountain of xeric (Las Derrumbadas) and the other of temperate (El Pinal) climate. We collected a total of 1113 beetles of 14 species. While abundance was similar between mountains, the number of species found on the temperate mountain (589 individuals: 11 species) was higher than on the xeric mountain (524 individuals: 5 species). On the temperate mountain, the disturbed habitat was approximately twice as diverse as the conserved habitat, while the opposite pattern was observed on the xeric mountain. Analysis of species turnover between mountains indicated the presence of two relatively different communities and the magnitude of the species turnover related to habitat disturbance depended on the type of mountain, having a higher turnover between habitat types in the temperate mountain. The xeric mountain was dominated by species belonging to the Paleoamerican Plateau distribution pattern, while the Paleoamerican Montane pattern dominated on the temperate mountain, whose species increased their abundance in disturbed habitats together with species of Nearctic affinity. Our results suggest a negative effect of habitat disturbance on the xeric mountain. While on the temperate mountain, beetle diversity seems to increase with disturbance. These results reiterate the need to consider regional-scale historical and ecological processes in order to understand the effects of disturbance and permit the establishment of conservation strategies to adequately protect the organisms, as well as the functions they provide for natural and anthropic ecosystems alike.     

Regional and local influence of grazing activity on the diversity of a semi-arid dung beetle community

This study analyses the effect of resource availability (i.e. sheep dung) on dung beetle communities in an arid region of Central Spain, both at regional and at local scales. A total of 18 sites within 600 km² were sampled for the regional analysis and 16 sites within the 30 km² of an Iberian municipality were sampled for the local analysis. Spatial and environmental characteristics of sampling sites were also compiled at both scales, including measures of grazing activity (livestock density at regional scale, and two counts of rabbit and sheep dung at local scale). At a regional scale, any environmental or spatial variable can help to explain the variation in abundance. However, species richness was related to summer precipitation and composition was related to elevation. At local scale, abundance is not significantly related to any of the environmental variables, but species richness was related to the local amount of sheep dung (27% of variance). The amount of dung in a 2‐km buffer around the site accounts for 27–32% of variance in abundance and 60–65% of variance in species richness. The presence of the flock with the highest sheep density explains 53% of abundance variability and 73% of species richness variance. A cluster analysis of localities identified two main groups, one characterized by a lower abundance and species richness that can be considered a nested subsample of the species‐rich group. The mean and maximum amount of sheep dung in the sites separated by less than 2 km are the only significant explanatory variables able to discriminate both groups. These results suggest that grazing intensity (and the associated increase in the amount of trophic resources) is a key factor in determining local variation in the diversity and composition of dung beetle assemblages. However, dung beetle assemblages are not spatially independent at the analysed resolution, and the amount of dung in the surroundings seems to be more important for locally collected species than the dung effectively found in the site. Although differences in the availability and quantity of trophic resources among nearby sites could be affecting the population dynamics and dispersion of dung beetles within a locality, sites with larger populations, and greater species numbers would not be able to exercise enough influence as to bring about a complete local faunistic homogenization.     

Vegetative communities as indicators of ground beetle (Coleoptera: Carabidae) diversity

Accurately measuring biodiversity is essential for successful conservation planning. Due to biodiversity’s complexity, specific taxa are often chosen as indicators of patterns of diversity as a whole. Such taxa can include vegetation which can inform conservation decisions by demarcating land units for management strategies. For land units to be useful, they must be accurate spatial representations of the species assemblages present on the landscape. In this study, we determined whether land units classified by vegetative communities predicted the community structure of a diverse group of invertebrates—the ground beetles (Coleoptera: Carabidae). Specifically, that (1) land units of the same classification contained similar carabid species assemblages and that (2) differences in species structure were correlated with variation in land unit characteristics, including canopy and ground cover, vegetation structure, tree density, leaf litter depth, and soil moisture. The study site, the Braidwood Dunes and Savanna Nature Preserve in Will County, Illinois is a mosaic of differing land units. Carabid beetles were sampled continuously with pitfall trapping for 1 year (excluding winter) from September 2011 to November 2011 and from March 2012 to September 2012. Land unit characteristics were measured in July 2012. Nonmetric multidimensional scaling (NMDS) ordinated the land units by their carabid species assemblages into five ecologically meaningful clusters: disturbed, marsh, prairie, restoration, and savanna. The subset of land unit characteristics with the highest rank correlation with the NMDS ordination included soil moisture, leaf litter depth, percentage of canopy cover, and percentage of grass ground cover. Land units classified by vegetative communities effectively represented carabid species assemblages.     

Influence of abiotic factors on spider and ground beetle communities in different salt-marsh systems

Salt marshes are interesting and endangered ecosystems in West-Europe. Nevertheless, their arthropod fauna remains largely unknown and the factors determining assemblages at micro-habitat scale are poorly understood. Few data are also available about the effects of management measures in salt marshes and how to monitor them. The aim of the present study is to determine the major factors structuring two dominant communities of arthropods, spider and ground beetles, in natural, managed (cutting and sheep grazing) and invaded (by the grass Elymus athericus) salt marshes. The two taxa were studied during 2002 and 2003 in different salt marshes of the Mont Saint-Michel Bay (NW France) by pitfall traps and hand-collecting. A total of 12 350 spiders (57 species) and 16 355 ground beetles (34 species) were caught during the study and analysed with respect to effects of the salinity gradient and of habitat structure characteristics. Spiders and ground beetles reacted differently to environmental factors in salt marshes. Spiders could more easily cope with salinity and their presence/absence was less related to the salinity than that of ground beetles. For ground beetles, there were few other community-structuring environmental factors and these were only related to the edaphic environment: species restricted to open habitats, significant effects of moisture content and salinity revealed by CCA. Because they are likely to bring complementary information on abiotic factors, we finally suggest using both spiders and ground beetles for monitoring the effects of management practices in salt marshes.     

Influence of tree species and soil properties on ground beetle (Coleoptera: Carabidae) communities

Although Carabidae is among the best-studied families of beetles in Europe from the faunistic point of view, there is still a lack of available information on the ecological requirements of the particular carabid species. The habitat preferences that determine the distribution of species are largely influenced by habitat structure and microclimate. In addition to other factors, these habitat parameters are influenced by the nature of the vegetation. Therefore, our study investigated the influence of tree species on carabid beetle communities. We conducted the research at 9 stands in the Borová Hora Arboretum (Zvolen, Central Slovakia). Each studied site represents a monoculture of one of nine tree species. At each site, some soil and leaf litter attributes (pH, conductivity, and content of H, C, N and P) were evaluated. Ground beetles were collected by pitfall trapping during the vegetation periods in 2008–2011. In total, 3012 individuals of 29 species were obtained. Significant differences in the total dynamic activity and species richness of the carabid beetle communities among the compared forest stands were revealed. The results of the research confirmed statistically significant relationships among 1) the soil conductivity and both the richness and Shannon diversity of the ground beetle communities, 2) the litter and soil N content and richness, the Shannon diversity and the species composition of the ground beetle communities. The Shannon diversity and richness were negatively related to the soil conductivity and positively related with the N content. Our research showed that dominant tree species indirectly influence diversity and composition of carabid communities via the soil properties.     

Behavioral adaptations imply a direct link between ecological specialization and reproductive isolation in a sympatrically diverging ground beetle

Adaptation to a previously unoccupied niche within a single population is one of the most contentious topics in evolutionary biology as it assumes the simultaneous evolution of ecologically selected and preference traits. Here, we demonstrate behavioral adaptation to contrasting hydrological regimes in a sympatric mosaic of Pogonus chalceus beetle populations, and argue that this adaptation may result in nonrandom gene flow. When exposed to experimental inundations, individuals from tidal marshes, which are naturally subjected to frequent but short floods, showed a higher propensity to remain submerged compared to individuals from seasonal marshes that are inundated for several months. This adaptive behavior is expected to decrease the probability that individuals will settle in the alternative habitat, resulting in spatial sorting and reproductive isolation of both ecotypes. Additionally, we show that this difference in behavior is induced by the environmental conditions experienced by the beetles during their nondispersive larval stages. Hence, accidental or forced ovipositioning in the alternative habitat may induce both an increased performance and preference to the natal habitat type. Such plastic traits could play an important role in the most incipient stages of divergence with gene flow.     

Heathland management effects on carabid beetle communities: the relationship between bare ground patch size and carabid biodiversity

Carabid beetles were sampled by pitfall trapping on Brentmoor Heath, Surrey, UK during the summers of 2009 and 2010 to determine the effects of bare ground patch size on beetle abundance, richness and diversity. Four patch sizes were investigated: 1, 4, 25 and 100?m² as well as the adjacent mown and unmown areas. A range of environmental parameters relating to soil characteristics, stones and nearby vegetation were measured at each patch and control habitat in order to distinguish the effect of patch size. Results show that bare ground is a valuable habitat for carabids, but that the response of their abundance, richness and diversity to bare ground patch size depends on a large number of environmental variables on and around the patches. When all variables are taken into account, smaller patches appear to benefit carabid abundance, richness and diversity. In the presence of Molinia caerulea at the patch edges, however, larger patches were more beneficial. Given this dependence on environmental variables, the perfect patch size for conservation of biodiversity is likely to be site specific and the best approach may be to use a variety of patch sizes at a range of successional stages.     

The importance of streamside sandbars to ground beetle (Coleoptera, Carabidae) communities in a deciduous forest

We used pitfall traps to sample ground beetles on sandbars along a small woodland stream and in the adjacent floodplain forest (Oglethorpe Co., GA, USA). We captured a total of 1,477 ground beetles representing 41 species. Twenty-two species were exclusive to sandbars, while eight were found only in the forested habitat. Ground beetles were captured in significantly greater numbers from sandbars, especially Brachinus janthinipennis and Omophron americanum. The B. janthinipennis record represents a new state record for the species. This study demonstrates that many unique species can be found in specialized microhabitats and emphasizes the need for biodiversity assessment surveys to include a wide range of these microhabitats within a survey area. In addition, it appears that many generalist forest species might use sandbars seasonally to exploit available resources. The U.S. Government's right to retain a non-exclusive, royalty-free license in and to any copyright is acknowledged.     

The wealth of species: ecological communities, complex systems and the legacy of Frank Preston

General statistical patterns in community ecology have attracted considerable recent debate. Difficulties in discriminating among mathematical models and the ecological mechanisms underlying them are likely related to a phenomenon first described by Frank Preston. He noted that the frequency distribution of abundances among species was uncannily similar to the Boltzmann distribution of kinetic energies among gas molecules and the Pareto distribution of incomes among wage earners. We provide additional examples to show that four different 'distributions of wealth' (species abundance distributions, species–area and species–time relations, and distance decay of compositional similarity) are not unique to ecology, but have analogues in other physical, geological, economic and cultural systems. Because these appear to be general statistical patterns characteristic of many complex dynamical systems they are likely not generated by uniquely ecological mechanistic processes.     

How season of grazing and herbivore selectivity influence monsoon tall-grass communities of northern Australia

Abstract. The hypothesis that season of defoliation and herbivore selectivity may be as important as level of use in determining plant community response to grazing was tested in a monsoon grassland in northern Australia. Plots, dominated by the tussock grasses Themeda triandra and Chrysopogon fallax, were grazed by cattle at low, medium and high rates of utilization in either the early wet, late wet or dry seasons. Effects of grazing on species composition were greatest in the early wet season when high rates of utilization significantly reduced the proportion and occurrence of Themeda and increased the proportion of forbs. Grazing in the dry season had no significant effect on composition. At medium and high levels of utilization in the early wet season, the pasture responded negatively to defoliation, only partially compensating for plant tissue lost to herbivory. The negative response to defoliation carried over to the next wet season when these same medium and high-grazing treatments produced only 80 % and 60 % growth, respectively, of that in treatments grazed at low levels of utilization or those grazed during the dry season. The frequency of Themeda was still lower, and that of annual grasses and non-leguminous forbs higher, in plots that had been grazed at a high rate of utilization for just eight weeks in the early wet season two years previously. Species richness and diversity were also significantly affected by this grazing disturbance. If species composition is to be maintained in these grasslands then stocking rates must be set at low levels to cope with the combined effect of undercompensation in response to defoliation in the wet season and strong dietary preferences for grazing sensitive species.     

Temporal dynamics of the fish communities in the reservoir: the influence of eutrophication on ecological guilds structure

Ichthyological Research - Construction of dams on rivers can lead to changes in water flow and nutrient cycling due to impediments to the flow of basic nutrients. The hypothesis that the division...     

Grass and ground dwelling beetle community responses to holistic and wildlife grazing management using a cross-fence comparison in Western Kalahari rangeland,Namibia

Journal of Insect Conservation - Savannahs are often branded by livestock grazing with resulting land degradation. Holistic management of livestock was proposed to contribute to biodiversity...     

The influence of hydrological regime and grazing management on the plant communities of a karst wetland (Skealoghan turlough) in Ireland

Question: What is the influence of hydrological regime, soils and management on the plant community composition and species richness of Skealoghan turlough (groundwater dependent calcareous wetland). Location: Skealoghan turlough, County Mayo, Ireland. Methods: Percentage cover of vascular plants and bryophytes were recorded, and data on hydrological regimes, soils and management were collected. Data were analysed using multivariate statistical techniques. Results: A total of 69 species of vascular plants and mosses were recorded. Cluster analysis grouped the samples into two separate communities, the Cirsio‐Molinietum and the Ranunculo‐Potentilletum anserinae plant communities. The plant community composition and species richness followed a main gradient down into the turlough basin, but also varied with microtopography, resulting in a mosaic of vegetation types. Conclusions: The biodiversity and conservation value of the site is linked to the heterogeneity in its physical environment in which hydrology, soils and grazing management all play critical roles.     

The influence of hydrology on the structure of invertebrate communities in two streams flowing into Lake Nakuru,Kenya

Stream fauna communities were studied in the Baharini Springbrook and the Njoro River, which flow into Lake Nakuru. The streams have significantly different flow regimes. Consequently, discharge-related factors influence their faunal composition and abundance. The Baharini Springbrook is perennial, slow-flowing with low steady discharge, a higher conductivity and a low conductivity gradient along its course. The Njoro River is intermittent, fast-flowing with a higher and variable discharge, lower conductivity and a steeper conductivity gradient. Due to its permanent and steady surface stream flow, the Baharini Springbrook has a higher number of invertebrate species and higher abundances than the Njoro River. However, in spite of the intermittent nature of the Njoro River, during periods of relatively steady discharge the composition of its fauna is similar to that of the Baharini Springbrook. Similarity in the substratum characteristics of the two streams and their close proximity is a possible explanation for the close relationship in their faunal composition. At the onset of flow after a drought, rapid colonisation of the lowland intermittent stretch of the Njoro River occurred probably by drift from upstream perennial sections and/or from the hyporheos. Initial small spates at the onset of surface flow seem not to affect the invertebrate abundance, but later bigger spates during and after much heavier rains reduced the faunal abundance significantly. The recovery of faunal abundance to pre-flood levels in the Njoro River was completed in 27 days. Taxon richness was, however, less affected by the spates.