Invasions by ladybugs, ladybirds, and other predatory beetles

Abstract

Species of predatory Coleoptera have become abundant in new geographic regions recently, raising concerns for invaded ecosystems. We address this topic by focusing on invasive alien ladybird beetles (Coccinellidae; known also as ladybugs). Humans appear directly or indirectly responsible for all or most ladybird invasions. Factors hypothesized to have promoted ladybird invasions include genetic diversity (e.g., for polymorphism), phenotypic plas- ticity, adaptation and genetic shift, generalized diet and habitat preferences, flexible life history and reproduction, large body size, and release from enemies. Factors such as climate, habitat and prey availability, and biotic resistance may sometimes prevent or slow ladybird invasions. Indigenous spe- cies (e.g., herbivores) may suffer from invasions, and biological control programs may be affected. Species of indigenous ladybirds throughout the world are reported to have declined in abundance following ladybird invasions, with increased competition and/or intraguild predation most often hypothesized or inferred. Similar recent studies especially of ground beetles (Carabidae) also make clear the potential of invasive alien predatory Coleoptera to disrupt invaded natural and agricultural ecosystems.