Has the diversity of flying aphids changed over the past 70 years? An analysis of Scottish suction trap data.

In recent years much has been written about insect declines in response to global anthropogenic drivers. Aphids are a widespread and often abundant component of insect communities; due to their biology and life cycle, they provide an excellent indicator of changing environmental conditions. The UK suction trap network has been operating for several decades now and is used to monitor aphid flights and virus risk to agricultural crops. Previous analysis has shown temporal changes in aphid pesticide resistance and aphid phenology, and declines in individual aphid taxa, but the datasets have not yet been used to examine insect biodiversity trends and drivers at a regional scale. Using these long-term datasets of flying aphids from suction trap sites in eastern and southern Scotland, we examine the temporal trends in aphid diversity, composition and abundance and their relation to several environmental conditions.

Our analysis of Scottish suction trap data shows that flying aphid diversity (Shannon Index) and abundance has increased over recent decades, particularly in May–June, correlating with increasing temperatures. More detailed examination shows this diversity increase results from accelerated aphid first flight in spring, which is driven by warmer over-wintering temperatures. Principal co-ordinates analysis reveals the seasonality of aphid abundance and highlights the aphid taxa associated with high diversity in May–June. The application of time-varying autoregressive models to aphid abundance data highlights that year-to-year autocorrelation increases with aphid abundance, while distributed-lag modelling reveals this autocorrelation is strengthened under warmer winter temperatures.

Further work is planned to understand the role of land use change in these trends. Ultimately, we aim to determine whether specific taxa or groups of taxa act as indicators of environmental change. Wider ecosystem impacts will be informed by in-depth knowledge of the ecology of aphids, aiding predictions about how biodiversity will responses to future climatic conditions and land use scenarios.