New prospects for insects’ diversity monitoring: assessment of the insect decline during the 20th century and development of a new multi-locus marker

Population genomics provide extensive demographic data for unravelling population evolution and patterns. Disentangling the baseline of insect’s population in the past is crucially important for a better understanding of their current state, the species’ evolutionary potential and to improve prediction models (Didham et al., 2020; Waldvogel et al., 2019). Little is known about the particular demographic history leading to the ongoing genetic erosion and population extinction (Schmid et al., 2018). Here, using the recently developed hyRAD (Suchan et al., 2016) hybridization-capture technique on insect museum collections, we aim at understanding the insect population dynamics across the 20th century. Museum collections have proven to be a highly valuable record of past biodiversity, whose DNA has been underused until recently (Kharouba et al., 2019; Meineke et al., 2019). Thanks to the development of new techniques based on Next Generation Sequencing (NGS) (Suchan et al., 2016), the damaged historical DNA contained by the ca. billion of collection specimens preserved across Museums around the world, is now available and of increasingly higher quality, opening the door to a new source of information (Gauthier et al., 2020; McCormack et al., 2016; Schmid et al., 2018). Therefore, in chapter 1, we aim to track the decline of insect populations from the beginning of 20th century in Switzerland.