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

Cherrill, Andrew

doi:10.14411/eje.2015.058

Cited by 11 publications

(9 citation statements)

References 25 publications

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“…It should be borne in mind, however, that some specimens may have been sucked into the samples from beyond the immediate sampling areas. Such peripheral suction effects can inflate numbers when air is drawn through gaps between the ground and the enclosure used to delimit the sample area (Cherrill, 2015). This may also occur when a suction sampler is raised and lowered from the ground.…”

Section: Resultsmentioning

confidence: 99%

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

Zentane

Quenu

Graham

et al. 2016

Insect Conserv Diversity

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The efficiency of VortisTM 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 Vortis TM 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 Vortis TM . These differences may have contributed to the larger 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.

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Section: Resultsmentioning

confidence: 99%

“…The cylinder delimited a sample area larger than the G-vac collecting nozzle and prevented inadvertent capture of invertebrates from adjacent vegetation (Cherrill, 2015). The cylinder was 60 cm in height and weighed 5 Kg (sufficient in weight to form a seal around its base with the ground surface).…”

Section: Operation Of the G-vacmentioning

confidence: 99%

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

Zentane

Quenu

Graham

et al. 2016

Insect Conserv Diversity

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“…Macleod et al (1994) used a G-vac to repeatedly sample the same unenclosed point with consecutive touch-downs up to a total duration of 160 s. Cumulative numbers of Coleoptera and Araneae increased from the first 5 s sub-sample to 30 s but not thereafter. The time after which no further benefit accrued may have been overestimated because specimens were probably drawn in from surrounding vegetation as the G-vac was repeatedly raised and lowered (Samu et al 1997, Cherrill 2015. This problem was overcome by Bell et al (2000) and Brook et al (2008) who sampled independent points for different durations.…”

Section: Discussionmentioning

confidence: 99%

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

Cherill¹,

Burkmar²,

Quenu³

et al. 2018

Entomol. Fennica

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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.

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“…although it can be mitigated by enclosing the sampling area (Cherrill, 2015). Other factors, such as time of day, weather conditions and time spent suction sampling, may also influence the outcomes (Bell et al, 2000;Brook et al, 2008) Döring et al, 2012;Hoback et al, 1999;Sétamou et al, 2014).…”

Section: Considerations When Choosing Sampling Methods For Null Netwo...mentioning

confidence: 99%

Sources of prey availability data alter interpretation of outputs from prey choice null networks

Cuff,

Tercel,

Windsor

et al. 2024

Ecological Entomology

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Null models provide a valuable baseline against which fundamental ecological hypotheses can be tested and foraging choices that cannot be explained by neutral processes or sampling biases can be highlighted. In this way, null models can advance our understanding beyond simplistic dietary descriptions to identify drivers of interactions. This method, however, requires estimates of resource availability, which are generally imperfect representations of highly dynamic systems. Optimising method selection is crucial for study design, but the precise effects of different resource availability data on the efficacy of null models are poorly understood. Using spider–prey networks as a model, we used prey abundance (suction sample) and activity density (sticky trap) data, and combinations of the two, to simulate null networks. We compared null diet composition, network properties (e.g., connectance and nestedness) and deviations of simulations from metabarcoding‐based spider dietary data to ascertain how different prey availability data alter ecological interpretation. Different sampling methods produced different null networks and inferred distinct prey selectivity. Null models based on prey abundance and combined frequency‐of‐occurrence data generated null diet compositions, which more closely resembled the diet composition determined by metabarcoding. Null models based on prey abundance, activity density and proportionally combined data generated null network properties most like the networks constructed via dietary metabarcoding. We show that survey method choice impacts all aspects of null network analyses, the precise effects varying between methods but ultimately altering ecological interpretation by increasing disparity in network properties or trophic niches between null and directly constructed networks. Merging datasets can generate more complete prey availability data but is not a panacea because it introduces different biases. The choice of method should reflect the research hypotheses and study system being investigated. Ultimately, survey methods should emulate the foraging mode of the focal predator as closely as possible, informed by the known ecology, natural history and behaviour of the predator.

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

Cited by 11 publications

References 25 publications

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

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

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

Sources of prey availability data alter interpretation of outputs from prey choice null networks

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

Cited by 11 publications

References 25 publications

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

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

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

Sources of prey availability data alter interpretation of outputs from prey choice null networks

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

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