The potential of native parasitoids for the control of Mexican bean beetles: A genetic and ecological approach

Bruchid beetles in the genus <i>Zabrotes</i> are important pests of field and stored beans all around the world and cause enormous economical losses in Mexico and Central America. Native parasitoids have been successfully used to suppress infestations by bruchid beetles in Africa, but few studies have assessed their potential to reduce seed damage in the New World and no successful biological control programs have been implemented, mainly due to the poor knowledge on their biology, systematics and ecology in this region. In this study, we used molecular tools to describe a new complex of three parasitoid species of bruchid beetles in the genus <i>Horismenus</i>, and investigated the level of gene flow and presence of ecotypes in this complex. We also examined the specific association between species of <i>Horismenus</i> and two sibling species of <i>Zabrotes</i> beetles, in order to evaluate their potential as biological control agents. Microsatellite data support the previous morphological description of three species, <i>H. butcheri</i>, <i>H. missouriensis</i> and <i>H. depressus</i>, but suggest some gene flow between <i>H. missouriensis</i> and <i>H. depressus</i>. Host-plant is shown to be the most important factor determining the ecological distribution of the two <i>Zabrotes</i> species, whereas altitude explains most of the distribution of the three <i>Horismenus</i> species. These results complement our understanding of this tritrophic system, providing a solid base for a potential biological control program using native parasitoids.