Abstract
The study of animal diets has benefited from the rise of high-throughput DNA sequencing applied to stomach content or faecal samples. The latter can be fresh samples used to describe recent meals or older samples, which can provide information about past feeding activities. For most invertebrates, however, it is difficult to access ‘historical’ samples, due to the small size of the animals and the absence of permanent defecation sites. Therefore, sampling must be repeated to account for seasonal variation and to capture the overall diet of a species. This study develops a method to describe the overall diet of nest-building Hymenoptera, based on a single sampling event, by analysing prey DNA from faeces accumulated in brood cells. We collected 48 nests from two species of introduced paper wasps (Polistes chinensis Fabricius and P. humilis Fabricius) in the urban and peri-urban areas of Auckland, New Zealand and selected two samples per nest. One from brood cells in the outer layer of the nest to represent the most recent diet and one from brood cells in an inner layer to represent older diet. Diet differed between species, although both fed mainly on Thysanoptera, Lepidoptera and Acariformes. Prey taxa identified to species level included both agricultural pests and native species. Prey communities consumed were significantly different between inner and outer nest samples, suggesting seasonal variation in prey availability and/or a diversification of the wasps’ diet as the colony grows. We also show for the first time potential predation of marine organisms by Polistes wasps. Our study provides field evidence that Polistes wasps feed on agricultural pests, supporting the hypothesis that some social wasp species could have a suppressing effect on agricultural pests. The proposed methodology is readily applicable to other nest-building Hymenoptera and has the potential to provide comprehensive knowledge about their diet with minimum sampling effort. Such knowledge is essential to measure the ecological impact of invasive Vespidae and support the conservation of native invertebrate biodiversity.
Highlights
In recent years, the study of invertebrate diets has been improved through the application of molecular methods to detect trophic interactions (Sheppard et al 2005; Boyer et al 2013; González-Chang et al 2016)
Our study provides field evidence that Polistes wasps feed on agricultural pests, supporting the hypothesis that some social wasp species could have a suppressing effect on agricultural pests
The methodology presented here has the potential to greatly assist in the study of social wasp ecology
Summary
The study of invertebrate diets has been improved through the application of molecular methods to detect trophic interactions (Sheppard et al 2005; Boyer et al 2013; González-Chang et al 2016) These methods allow the sequencing of prey DNA present in the regurgitates (Waldner and Traugott 2012), gut contents (OlmosPérez et al 2017) or faeces (Boyer et al 2011) of predators. Recent developments in molecular techniques mean that even low-quantity and low-quality DNA samples can be analysed efficiently and applying these techniques to the analysis of faecal samples for assessing diet represents an interesting opportunity (Monterroso et al 2019; Waterhouse et al 2014) This could be a useful strategy for assessing seasonal variation in the diets of taxa who deposit their faeces in permanent sites such as latrines or other territory marking sites (Fretueg et al 2015). Such approach could provide valuable insight into the diet of nest-building Hymenoptera where larval faeces accumulate within the nest
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