Past, present, and future monitoring of insects sensitive to climate change

Abstract

Methods that can provide expediency in biodiversity and ecosystem assessments are becoming increasingly important in a shifting conservation landscape due to climate and land use change. Insects provide vital ecosystem services, yet the full scope, causes, and future implications of insect decline have yet to be fully understood. In this work, butterflies are utilized as ecological indicators of an ecosystem sensitive to climate change and as indicators for the development of novel molecular genetic techniques of surveying terrestrial insect biodiversity. Wildflower-associated environmental DNA (eDNA) has recently been used to identify insects and may provide an efficient and non-invasive alternative for monitoring terrestrial insect biodiversity. A resurvey effort of butterfly diversity in Glacier National Park, Montana using traditional netting surveys was conducted to assess the 2022 and 2023 butterfly community in comparison to survey data obtained 35 years earlier in 1988 and 1989. Information from the resurvey effort was used in comparative analyses to determine if molecular methods can detect butterflies at a similar or better resolution to traditional surveys and whether insect DNA sequence abundance correlates with known butterfly visitation. Comparison of the butterfly community in Glacier National Park from the past survey (1988-1989) to the present (2022- 2023) revealed that butterfly species richness and community composition did not change overall compared to 35 years ago, though considerable variation between the two present study years and the presence of distinct butterfly communities in habitats sensitive to climate change warrants further investigation and monitoring. High-quality and abundant insect sequences were obtained from wildflower-associated eDNA samples, and six unique butterfly taxa were identified, five of which were verified as present at the survey sites using traditional netting surveys on the same day as wildflower collection. Traditional survey methods captured 43 additional butterfly species that were not identified by eDNA, and butterflies that were physically placed or observed on the flower before collection were not detected. This work indicates the importance of continued traditional butterfly monitoring efforts while working in parallel with controlled experiments to further develop the protocols to reliably detect butterflies and other insects with flower-associated eDNA.