Evolution of mating and reproduction underlying invasions of a beetle pest

Abstract

Biological invasions are influenced and influence global changes and can affect the functioning of ecosystems, as well as threaten food security. The occurrence of such invasions is likely to increase dramatically, thus creating an urgent demand to better understand the underlying evolutionary aspects, such as biological mechanisms, which can contribute to the success and impact of an invasion. Despite the great advances that have occurred in this area, the mechanisms for the success of the initial invasion and the ideal strategies to promote the impact of the invasion are still debated. Particularly, and surprisingly, little attention has been paid to the roles of mating and reproduction systems in insects, even though they are among the worst invaders globally, both ecologically and economically. In these organisms, multiple mating of females (polyandry) can serve as a pre-adaptation for successful invasion, in order to overcome the inevitable depression by inbreeding after expansion has been achieved. Furthermore, adaptive changes in mating and reproductive traits in response to new selection scenarios are likely to increase the impacts of invasion. These changes may result from trade-offs between reproduction and starvation resistance and/or immunity due to the generally greater availability of food and the absence of pathogens in the invaded areas (also known as enemy release). Finally, estimates of trait heritability may differ between the endemic and invaded range (eg, mating, reproduction, starvation resistance, and immunity), thus reflecting the distinct selection scenarios underlying such evolutionary changes. However, empirical data that address these evolutionary mechanisms in a holistic manner remain scarce for invasive insect species. Here, we propose the use of the hive beetle, Aethina tumida Murray (Coleoptera: Nitidulidae), a bee nest parasite endemic to sub-Saharan Africa, as a model system to better understand the fundamental evolutionary aspects of biological invasions. Due to its near-global spread, long adult longevity, promiscuous mating system, and distinct impact on hosts of adapted bees vs. not adapted, the SHB constitutes an ideal model system. Using a global approach, we will consider selection scenarios in the endemic range, during displacement and after establishment in their new ranges. Behavioral, genetic, morphological and physiological data for phenotypic traits will be combined across multiple endemic and invasive populations to address: 1) polyandry as a pre-adaptation for successful invasion, 2) adaptive changes in mating and reproduction, 3) trade promotion -offs (adaptive changes) and 4) heritability estimates as indicators of distinct selection scenarios. Not only will the proposed research help to better understand and eventually mitigate invasive insect species, but the experience gained from the proposed new approaches will likely benefit the scientific community at large. (AU)