Suction sampling of grassland invertebrates using the G-vac: quantifying and avoiding peripheral suction effects

Suction sampling with modified garden leaf-blowers (G-vacs) is a widely used method for research on invertebrates in agricultural and grassland habitats. Approaches vary from sweeping the collecting nozzle across the surface of the vegetation within a known area, applying the nozzle firmly to the ground to delimit a sample area equal to nozzle crosssection, or applying the nozzle repeatedly within a larger open-ended cylinder placed on the ground. These approaches vary in potential for the inadvertent capture of specimens from outside of the sample area as a result of air being drawn into the nozzle from adjacent vegetation. This has never been studied adequately and is defined here for the first time as the Peripheral Suction Effect (PSE). Invertebrate species are likely to differ in susceptibility to PSE and so both sample size and composition could be impacted. This study compares two series of samples of Auchenorrhyncha taken using the same G-vac suction sampler (nozzle area, 0.01 m2) from areas enclosed and unenclosed by an openended cylindrical enclosure (area 0.17 m2) intended to prevent PSE. The unenclosed samples contained greater numbers of leafhoppers including Arthaldeus pascuellus, Javesella pellucida and immature Deltocephalinae. Numbers of immature Delphacinae did not differ between enclosed and unenclosed samples. The species composition of the two series of samples was similar, but the proportional representation of immature Delphacinae in unenclosed samples was diluted by the inflated numbers of other taxa that were drawn from the surrounding area. Peripheral suction effects are taxa-specific and therefore have the potential to bias measures of invertebrate community composition. Use of an open-ended cylinder to delimit the sample area is recommended as a simple, inexpensive and effective method of avoiding problems associated with PSE when using a G-vac. The potential for PSE with other models of suction samplers is discussed and questions for further research are identified

Inter-observer variation in habitat survey data: investigating the consequences for professional practice

Knowledge of the extent and distribution of vegetation types is essential to underpin conservation assessments, land-use planning and management of wildlife populations (Hill et al. 2005; IEEM 2006; Morris and Thrivel 2009). Despite improvements in remote sensing of land cover, field survey remains an essential method for collection of data on the distribution of habitats and their floristic composition (IEEM 2006). Surveying of vegetation is recognised as a key skill required by ecologists and environmental managers (IEEM 2007, 2011), but studies of variability between surveyors have often revealed significant levels of disagreement in terms of the plant species and habitats recorded (e.g. Scott and Hallam 2002; Milberg et al. 2008; Stevens et al. 2004; Hearn et al. 2011). For example, a study using the National Vegetation Classification (NVC) in the UK found that pairwise spatial agreement between seven surveyors mapping vegetation at the same site averaged only 34% at the community level (Hearn et al. 2011). Comparisons between plant species lists drawn up by different surveyors working in the same plots typically show agreement in the range of 50%–70% for a variety of habitats (Scott and Hallam 2002). Professionals working in the environmental and conservation sectors are therefore aware of the potential for inter-observer variation and its impact on data quality, but there is a dearth of information on the extent to which it is perceived to be an impediment to good decision-making in practice (Cherrill 2013a). If inter-observer variation causes few problems, then the issue may be largely irrelevant in day-to-day practice. However, if inter-observer variation in interpretation of habitat types is a cause of disagreement and poor decision-making there may be a mandate to change training and/or survey methods. The focus of the present study is inter-observer variation in habitat mapping using two of the standard classifications in the United Kingdom, namely the Phase 1 habitat classification (JNCC 1993) and the NVC (Rodwell 2006). Studies focussing on these methods have revealed spatial agreement between surveyors using the same method at the same site in the range of 25%–70% (Cherrill 2013a). These studies, however, were conducted either as bespoke academic research projects designed to directly assess observer variation (Cherrill and McClean 1995, 1999a, 1999b, 2000, 2001; Hearn et al. 2011) or as part of Quality Assurance procedures within a large-scale national monitoring programme designed to detect landscape change (Stevens et al. 2004). The extent to which these results are representative of inter-observer variation in professional practice involving environmental assessment and site management planning is therefore unknown (Cherrill 2013a). None the less, it can be hypothesised that errors made in identifying vegetation types in these spheres of activity may be frequent and that there may be consequences for conservation assessments, site management and planning decisions. The present paper uses a questionnaire survey of members of the Chartered Institute of Ecology and Environmental Management (CIEEM) in the United Kingdom to address two main questions. First, how frequently are errors in data detected in reports describing the results of vegetation surveys? Second, what are the practical consequences of these errors? CIEEM has approximately five thousand members in the UK. They are ideally placed to respond to these questions being employed primarily in environmental consultancy, planning authorities, governmental environmental agencies, and non-governmental conservation organisations. The Phase 1 and NVC survey methods are used only in the UK, but similar approaches are used elsewhere (Alexander and Millington 2000). The wider applicability of the study is, therefore, to illustrate the need to extend academic studies of inter-observer variation to investigate their relevance to the day-to-day experiences of environmental professionals. The implications for further research and development of professional practice are discussed

Large-scale spatial patterns in species richness of orthoptera in the Greater London Area, United Kingdom: Relationships with Land Cover

This paper explores species richness of insects of the order Orthoptera (grasshoppers, crickets, etc.) along spatial gradients defined using remotely sensed land cover data for an area of 5600 km2 centred on the city of London. The number of species within grid-squares of a national atlas, controlled for recording effort, declined along composite multivariate spatial gradients representing landscapes with increasing dominance of arable and urban land uses, yet was uncorrelated with the area of an individual land cover representing cultivated land, and only weakly correlated with a second land cover representing urban development. Few orthopteran species reside directly within either arable crops or non-vegetated urban land covers. Thus, whilst the areas of the individual land covers are intuitively sensible (and simple) measures of agricultural and urban cover respectively, their areas do not capture ecologically relevant information about variation in the composition of the uncultivated and non-urban land cover matrices within which the species actually reside. The results illustrate the advantages of using multivariate data reduction techniques (such as the Principle Components Analysis applied here) to describe spatial gradients in the extent of agricultural and urban influence. Relatively few landscape scale studies have focused on insects and the present study illustrates a) the potential for using Orthoptera to explore issues of biodiversity in the landscape and to monitor impacts of land use via analysis of large-scale spatial patterns from national species distribution atlases combined with remotely sensed land cover, and b) the importance of selecting appropriate measures of land use which incorporate information on the complex mix of land cover types utilised by the species under investigation

Species richness of Orthoptera declines with elevation while elevational range of individual species peaks at mid elevation

Species richness has been shown to decrease, and elevational range increase (the Rapoport effect), with elevation as a consequence of biotic and abiotic factors, but patterns are inconsistent across taxonomic groups. Despite being an important indicator taxon and a component of local communities, Orthoptera distributions at higher elevations in Europe remain unclear. We investigated the relationship of Orthoptera species richness and elevational range with elevation in the Pyrenees mountains, Europe. We conducted sweepnetting surveys supplemented by hand-sampling, at 28 sites stratified by elevation, across three study areas. Using generalised linear models, we found that species richness declined with elevation. Elevation was an important predictor of species richness, but sampling effort and vegetation structure (height and cover) also contributed to estimates of species richness. Using a nonlinear regression to model the elevational range of species over the elevational gradient, we did not observe a Rapoport effect, with elevational range peaking at mid-elevation instead. Smaller elevational ranges of species found at high elevations may be due to a combination of sampling over a restricted elevational range and the presence of specialist high-elevation species. We argue that our findings are useful for understanding species distributions with elevation at the interface between local and regional scales. Clarifying the biotic and abiotic predictors of species distribution is important for informing conservation efforts and predicting consequences of climate change

Suction samplers for grassland invertebrates: comparison of numbers caught using Vortis™and G-vac devices

1. The efficiency of Vortis TM and a modified garden leaf-blower/vacuum ‘G-vac’ sampler were compared by sampling invertebrates using standardised sample areas and suction times at three grassland sites. The G-vac caught more individuals of Araneae, Auchenorrhyncha, Thysanoptera and Hymenoptera than the Vortis. Numbers of Diptera did not differ between devices, but the VortisTM captured greater numbers of Coleoptera. 2. Estimated air velocity within the collecting nozzle was greater for the G-vac and its mode of application resulted in greater disturbance of the grass sward than with the VortisTM. These differences may have contributed to the lar- ger captures of certain taxa by the G-vac. 3. It is concluded that G-vacs can be applied with confidence as a credible alternative to the bespoke Vortis TM, and particularly for taxa which are most frequently sampled using suction samplers

Suction duration and numbers of Araneae and Auchenorrhyncha collected in grassland when using an open-ended cylinder to define the sample area

Suction samplers are typically used with touch-down samples, where the nozzle is held stationary on the ground, or within an open-ended cylinder, where the nozzle is moved through the enclosed vegetation. With touch-down sampling, published estimates suggest that virtually all individuals and species of grassland invertebrate are captured within 3 s. Effects of suction duration on catch when sampling within a cylinder have rarely been investigated. Here, it was found that extrapolation from studies of touch-down sampling, based on the relative areas of the G-vac nozzle and the cylinder, can be used to guide minimum sampling durations for Auchenorrhyncha (leafhoppers and planthoppers) when using a G-vac. Additional time, however, may be necessary when sampling Araneae (spiders), probably because movement of the G-vac nozzle within the cylinder results in disturbance of the vegetation such that more specimens are made available to be captured than with touch-down sampling

Lower pollen nutritional quality delays nest building and egg laying in Bombus terrestris audax micro-colonies leading to reduced biomass gain

This version of the article has been accepted for publication, after peer review (when applicable) and is subject to Springer Nature’s AM terms of use, but is not the Version of Record and does not reflect post-acceptance improvements, or any corrections. The Version of Record is available online at: http://dx.doi.org/10.1007/s13592-021-00885-3The performance of Bombus terrestris micro-colonies fed five diets differing in pollen species composition and level of nine essential amino acids (EAA; leucine, lysine, valine, arginine, isoleucine, phenylalanine, threonine, histidine, methionine) was assessed for 37 days by recording total biomass gain, nest building initiation, brood production (eggs, small and large larvae, pupae, drones), nectar, and pollen collection. Stronger colony performance was linked to higher amino acid levels but no consistent differences in biomass gain were recorded between mono- and poly-species diets. Poorest performance occurred in micro-colonies offered pure oilseed rape (OSR) pollen which contained the lowest EAA levels. Reduced micro-colony development (delayed nest initiation and lower brood production) was related to OSR proportion in the diet and lower EAA levels. Results are discussed in relation to selection of plant species in the design of habitats to promote bee populations

PCR-based gut content analysis to identify arthropod predators of Haplodiplosis marginata

Saddle gall midge (Haplodiplosis marginata) is a cereal pest exhibiting sporadic outbreaks for which chemical control options are limited. Integrated Pest Management programs may offer a means of suppressing H. marginata outbreaks, reducing pesticide input. Many IPM programs benefit from the natural population suppression inflicted through predation and parasitism. The larval stage of H. marginata overwinters in the soil and may be preyed upon by ground-dwelling arthropods, however the natural enemies of H. marginata remain unrecognized. A PCR-based assay for detecting H. marginata in the guts of predators was designed using novel species-specific primers. Feeding trials involving H. marginata larvae showed a detectability half-life of 31.07 h post-feeding in Nebria brevicollis. The guts of field-caught Carabidae were screened for H. marginata DNA. Four species: Poecilus versicolor, Nebria brevicollis, Harpalus rufipes and Loricera pilicornis were identified as natural enemies of H. marginata for the first time. A higher proportion of positive results were obtained at the end of H. marginata emergence (July) compared to the beginning (May). The importance of understanding trophic interactions in the management of H. marginata is discussed in addition to the potential uses for the newly designed assay and primers

A review of the biology, ecology and control of saddle gall midge,Haplodiplosis marginata(Diptera: Cecidomyiidae) with a focus on phenological forecasting

Saddle gall midge Haplodiplosis marginata (Diptera: Cecidomyiidae) is a pest of cereals across Europe. The occasional nature of this pest has resulted in limited and sporadic research activity. There remain important gaps in knowledge due either to a genuine lack of research or to previous research being difficult to access. These knowledge gaps make the development of effective control options difficult. Here, we review the existing literature in an attempt to consolidate the information on H. marginata from research which spans several decades and encompasses many different countries. The current distribution and pest status of this insect are updated, along with the methods of cultural and chemical control available to growers. The biology and life history of the insect are described in detail and the ecological processes governing them are discussed. A forecasting model is presented which allows the emergence of this pest in the UK to be predicted from degree day data, and the potential application of this model in management decisions is discussed. Finally, the areas in most need of further research are identified, along with suggestions of how this information can be used to help develop effective and sustainable management solutions for this pest

Lower pollen nutritional quality delays nest building and egg laying in Bombus terrestris audax micro-colonies leading to reduced biomass gain

The performance of Bombus terrestris micro-colonies fed five diets differing in pollen species composition and level of nine essential amino acids (EAA; leucine, lysine, valine, arginine, isoleucine, phenylalanine, threonine, histidine, methionine) was assessed for 37 days by recording total biomass gain, nest building initiation, brood production (eggs, small and large larvae, pupae, drones), nectar, and pollen collection. Stronger colony performance was linked to higher amino acid levels but no consistent differences in biomass gain were recorded between mono- and poly-species diets. Poorest performance occurred in micro-colonies offered pure oilseed rape (OSR) pollen which contained the lowest EAA levels. Reduced micro-colony development (delayed nest initiation and lower brood production) was related to OSR proportion in the diet and lower EAA levels. Results are discussed in relation to selection of plant species in the design of habitats to promote bee populations