Eco-evolutionary responses in a native insect to plant invasion

Invasive alien species are one of the greatest threats to ecosystems and biodiversity globally. In this study I explored the evolutionary consequences of the invasive balloon vine, Cardiospermum grandiflorum, for the native Australian soapberry bug, Leptocoris tagalicus. My study focussed on L. tagalicus populations sampled on invasive C. grandiflorum and native Alectryon tomentosus, along Australia’s east coast. Field and laboratory observations confirmed that the insect has evolved longer proboscides on its new host plant. My breeding experiments indicated high narrow-sense heritability in proboscis length. Moreover, L. tagalicus enjoys higher fitness on this new host. Despite signals of disruptive selection on L. tagalicus beak length caused by differences in fruit size of invasive and native host plants, my genomic analyses suggested that gene flow is high between insect populations regardless of host plant and that insects can disperse over vast distances. I also identified two ancestral population genetic clusters for L. tagalicus which appear to have admixed recently, perhaps due to the invasion spread of C. grandiflorum. My study shows that shifts in interaction ecologies facilitated by invasive species may not only lead to a breakdown of historical barries of gene flow, but also to rapid evolutionary changes, in native species.