Using sedaDNA from California Holocene and Anthropocene lake sediments to determine drivers of the “Insect Apocalypse”

Stanford University, Stanford CA

Investigators

Abstract

Insects represent more than half of described species on earth and play critical roles in ecological processes, ecosystem function, and human well-being. Insect declines have been widely documented and causes of these declines are attributed to human impacts including climate change, habitat loss and degradation, agricultural intensification including pesticides, and introduction of non-native species. However, we do not yet understand the relative importance and synergies of each of these factors. Although we have detailed records of recent changes in insect diversity and abundance in some regions of the globe, longer-term records (>50 years) are rare. These long-term records are important for understanding when large scale insect declines began, how far it has progressed, and whether recent variations in insect populations are within the range of normal changes. Our understanding of this biodiversity crisis is also limited because previous work has mainly focused on certain groups of insects, like pollinators and butterflies, and we have little or no knowledge of whether or how other groups have been impacted. This research will analyze insect DNA from lake sediment cores in California to reconstruct a >1,200-year record of insect diversity change. By using DNA analysis, the researchers will be able to study insect species which have not previously received much research attention. The project will also assemble data on land use change, climate change, and pesticide applications, to link these human impacts with insect diversity through time. This research advances biodiversity conservation by improving our baseline understanding of insect declines, and distinguishing natural changes in insect diversity from those caused by human impacts over the last century. This project will contribute to the development of new research techniques and biodiversity monitoring technology. This project will utilize sediment cores collected from a marsh and hydrologically connected reservoir at Jasper Ridge Biological Preserve (JRBP) in the San Francisco Bay Area (California, USA). Together these cores span a period of increasing local and global human impacts. The researchers will employ both traditional palaeoecological tools as well as emerging sedimentary DNA (sedaDNA) techniques. To characterize insect diversity through time, the researchers will analyze sedaDNA from the sediment cores using metabarcoding and high-throughput sequencing. To develop high-resolution records of insect diversity change, the researchers will use geochemical and microfossil analyses, sedaDNA, and historical records. This multi-proxy, high-resolution data set will then be statistically queried using several multivariate modeling approaches. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.