Dispersal-behavioral plasticity within an insect-host system undergoing human-induced rapid environmental change (HIREC)

As environments change, often drastically, due to human activities, dispersal-behavioral plasticity can become a key mediator of metapopulation connectivity and the interactions between an individual and its altered environment. Our goal was to investigate the traits and ecological processes that affect plastic dispersal responses within an insect-host system undergoing human-induced rapid evolutionary change (HIREC). Since the 1960s, populations of the red-shouldered soapberry bug from Florida, USA, originally feeding on the seeds of Cardiospermum corindum on the islands, quickly adapted to feeding on an invasive, ornamental tree, Koelreuteria elegans, on the mainland, which led to host-specific wing polyphenism. Here, we measured the morphology of >3,500 soapberry bugs field collected from 2013 to 2020 and the flight performance of 378 total soapberry bugs tested in a flight mill during Fall 2019 and Winter 2020. Flight tests showed females and mainland natives exhibited variable flight responses mediated by mass, while males were consistent, wing-dependent flyers. However, historical specimens showed annual rises in flightless morphs for males and dwindling wing-to-body sizes for island natives since 2013. Despite uncertain future fitness consequences, plasticity could help predict mobility character and agent dispersal behavior and ultimately help identify whether recent trends signal adjustment or maladaptation to HIREC.