Using Malaise Traps and Metabarcoding for Biodiversity Assessment in Vineyards: Effects of Weather and Trapping Effort.

Abstract

Simple SummaryA strong decline in insect biomass and biodiversity has been observed in the past decades. Long-term monitoring programs are important to understand the reasons for changes in species occurrence, which are mostly attributed to habitat destruction, intensified agriculture, invasive organisms, and climate change. Metabarcoding, a procedure for identifying insect species in bulk samples based on their DNA sequences, provides a method to replace otherwise time-consuming species identification in a time- and cost-efficient way. In this study, we examined how weather and trapping effort affect biomass and biodiversity of Malaise trap catches in vineyards using metabarcoding. Most insects were caught during warm and hot weather. We observed that, as the number of trapping days and sites increased, there was a very high accumulation of taxa due to species with low abundance. The results can help in developing monitoring programs. Common species can be extensively surveyed with less effort, whereas rare taxa require excessive effort to be completely surveyed due to a lack of saturation. Thus, metabarcoding can play an important role in conducting monitoring by offsetting the additional effort required to detect rare species by making identification less time consuming and costlyMetabarcoding is a powerful tool for ecological studies and monitoring that might provide a solution to the time-consuming taxonomic identification of the vast diversity of insects. Here, we assess how ambient weather conditions during Malaise trap exposure and the effort of trapping affect biomass and taxa richness in vineyards. Biomass varied by more than twofold with weather conditions. It increased with warmer and drier weather but was not significantly related with wind or precipitation. Taxa richness showed a saturating relationship with increasing trapping duration and was influenced by environmental and seasonal effects. Taxa accumulation was high, increasing fourfold from three days of monthly trap exposure compared to continuous trapping and nearly sixfold from sampling at a single site compared to 32 sites. The limited saturation was mainly due to a large number of singletons, such as rare species, in the metabarcoding dataset. Metabarcoding can be key for long-term insect monitoring. We conclude that single traps operated for up to ten days per month are suitable to monitor the presence of common species. However, more intensive trapping is necessary for a good representation of rare species in biodiversity monitoring. The data collected here can potentially guide the design of monitoring studies.