Ants and agricultural pests in the Mediterranean: exploring antagonism and mutualism paradigms for biological control

Abstract

Ants are insects with an almost unparalleled ecological impact on terrestrial ecosystems, providing many important ecosystem services through their complex interactions with countless other organisms. Ant role in agroecosystems has drawn significant attention by humans for centuries but is still better investigated for the tropics as compared to temperate regions. Most ants are generalist predators, and their predatory abilities have also been appreciated for their antagonistic effects on many agricultural pest insects. At the same time, ants establish mutualistic relationships with several honeydew-producing hemipterans, forming keystone ecological associations that can also develop into a problem for agricultural settings in which some ant-mutualist hemipterans are important pests. We explore ecological and behavioral interactions between ants and agricultural pest insects through antagonism and mutualism paradigms using laboratory and field experiments, while also gathering baseline data on the diversity and distribution of ant species in agroecosystems across Italy. We present our results through eleven chapters grouped in three sections: i) Ants as biological control agents of insect pests; ii) Ants as mutualist partners of insect pests; iii) First data on ant diversity and distribution in Italian agroecosystems. In the first section, we describe for the first time the role of ants as natural enemies of key agricultural pests accounting both direct and direct interactions and analyzing potential conflicts with other natural enemies, while also presenting encouraging results on behavioral manipulation of ants through artificial nectaries. In the second section, we describe ecological and behavioral aspects of the interactions between ants, honeydew-producing mutualist hemipterans, and their natural enemies, emphasizing the variety of outcomes that the species-specific characteristics of the involved actors may produce. Furthermore, we present a comparative review of the methodologies developed to manage ant-hemipteran mutualism when this is responsible for significant pest outbreaks. In the third section, we present first data on ant diversity in Italian agroecosystems as well as the inclusion of the ant species studied in this thesis in the DNA barcoding library of European ants.