A century of social wasp occupancy trends from natural history collections: spatiotemporal resolutions have little effect on model performance

Galina M Jönsson,Gavin R Broad,Nick J B Isaac,Seirian Sumner

doi:10.1111/icad.12494

Abstract

ABSTRACT The current dearth of long‐term insect population trends is a major obstacle to conservation. Occupancy models have been proposed as a solution, but it remains unclear whether they can yield long‐term trends from natural history collections, since specimen records are normally very sparse. A common approach for sparse data is to coarsen its spatial and/or temporal resolution, although coarsening risks violating model assumptions. We (i) test whether occupancy trends of three social wasp (Hymenoptera: Vespidae: Vespinae) species – the common wasp (Vespula vulgaris), the German wasp (Vespula germanica) and the European hornet (Vespa crabro) – have changed in England between 1900 and 2016, and (ii) test the effect of spatiotemporal resolution on the performance of occupancy models using very sparse data. All models are based on an integrated dataset of occurrence records and natural history collection specimen records. We show that occupancy models can yield long‐term species‐specific trends from very sparse natural history collection specimens. We present the first quantitative trends for three Vespinae species in England over 116 years. Vespula vulgaris and V. germanica show stable trends over the time series, whilst V. crabro's occupancy decreased from 1950 to 1970 and increased since 1970. Moreover, we show that spatiotemporal resolution has little effect on model performance, although coarsening the spatial grain is an appropriate method for achieving enough records to estimate long‐term changes. With the increasing availability of biological records, the model formulation used here has the potential to provide novel insights by making use of natural history collections' unique specimen assemblages.

Highlights

Declining insect populations have been flagged as a cause for concern by scientists for over a decade (e.g., Conrad et al, 2006; Franzén & Johannesson, 2007; Harmon et al, 2007; Goulson et al, 2008; Shortall et al, 2009), but have only recently caught the public’s attention due to worldwide media coverage in response to alarming new studies
Our findings add to a nascent literature on long-term (>50 year) change in insect biodiversity from museum data (Habel et al, 2019; Soroye et al, 2020; Zattara & Aizen, 2021), to our knowledge this is the first to present century-long trends at the species level
We present the first quantitative V. vulgaris, V. germanica and V. crabro trends in England before the 1970s (Fig. 4)

Summary

Introduction

Declining insect populations have been flagged as a cause for concern by scientists for over a decade (e.g., Conrad et al, 2006; Franzén & Johannesson, 2007; Harmon et al, 2007; Goulson et al, 2008; Shortall et al, 2009), but have only recently caught the public’s attention due to worldwide media coverage in response to alarming new studies. Such studies include Hallmann et al (2017), suggesting that German insect biomass declines exceed 75% over 27 years, and Sánchez-Bayo & Wyckhuys (2019), who warn that 40% of global insect species may become extinct within a few decades. Responding to the continued degradation of insect populations and ecosystem services necessitates robust population trends over long temporal scales as well as large spatial scales, since drivers of change are more likely to be confounded for short-term local changes (Parmesan & Yohe, 2003; Root et al, 2003)

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Conclusion