Venom proteins from parasitoid wasps and their biological functions
Résumé
To develop efficient and safe biological control, we need to reliably identify natural
enemy species, determine their host range, and understand the mechanisms
that drive host range evolution. We investigated these points in Cotesia sesamiae,
an African parasitic wasp of cereal stem borers. Phylogenetic analyses of 74 individual
wasps, based on six mitochondrial and nuclear genes, revealed three lineages.
We then investigated the ecological status (host plant and host insect
ranges in the field, and host insect suitability tests) and the biological status
(cross-mating tests) of the three lineages. We found that one highly supported
lineage showed all the hallmarks of a cryptic species. It is associated with one host
insect, Sesamia nonagrioides, and is reproductively isolated from the other two
lineages by pre- and postmating barriers. The other two lineages had a more variable
phylogenetic support, depending on the set of genes; they exhibited an overlapping
and diversified range of host species and are not reproductively isolated
from one another. We discuss the ecological conditions and mechanisms that
likely generated this ongoing speciation and the relevance of this new specialist
taxon in the genus Cotesia for biological control.