Did the introduction of maize into Europe provide enemy‐free space to Ostrinia nubilalis? Parasitism differences between two sibling species of the genus Ostrinia

Abstract

We examined whether maize offers enemy‐free space (EFS) to its pest Ostrinia nubilalis, and may thereby have contributed to its divergence from the sibling species, Ostrinia scapulalis, feeding mainly on mugwort, when introduced into Europe five centuries ago. We collected Ostrinia larvae on maize (70 populations, 8425 individuals) and mugwort (10 populations, 1184 individuals) and recorded parasitism using both traditional (counting emerging parasitoids) and molecular methods (detection by specific polymerase chain reaction). The main parasitoid was Macrocentrus cingulum (Braconidae). On mugwort, parasitism was twice that on maize, and parasitoid‐related mortality was 8 times higher. This suggests that maize affords substantial EFS to Ostrinia feeding on it. The lower Mortality:Infestation ratio in maize suggests that O. nubilalis’ immune response might be stronger than that of O. scapulalis. If so, adapting to maize and diverging from O. scapulalis would decrease the impact of parasitism on O. nubilalis at both ecological and evolutionary levels.

Divergence in behaviour between the European corn borer,Ostrinia nubilalis, and its sibling speciesOstrinia scapulalis: adaptation to human harvesting?

“…with a new plant environment, while escaping some natural enemies (such as Macrocentrus cingulum, a braconid wasp; Pélissié et al 2010). It also encountered a new enemy: humans.…”

“…In addition, the two Ostrinia sibling species differ with respect to development time (Thomas et al (2003), but see Malausa et al 2005). Natural enemies could also have promoted the divergence, since both the identity of parasitoids and their prevalence differ between maize and mugwort (Thomas et al 2003;Pélissié et al 2010).…”

Prevalence rates of Wolbachia endosymbiotic bacterium in natural populations of Ostrinia Nubilalis and Ostrinia Scapulalis (Lepidoptera: Pyraloidea: Crambidae) in South-Western Russia

“…Предполагается, что одним из факторов, повлиявших на процесс перехода насекомых с двудольных на однодольные растения, по-служили перепончатокрылые наездники. Гусеницы, пи-тающиеся кукурузой, меньше подвержены поражению наездниками за счет эффекта «пространства, свободного от паразитов» (enemy-free space) [15]. Еще одним гипо-тетическим фактором изоляции популяций может вы-ступать матерински наследуемый симбионт Wolbachia, известный как репродуктивный паразит членистоно-гих [16].…”

Crop domestication, global human-mediated migration, and the unresolved role of geography in pest control

“…Furthermore, the two subpopulations respond to different isomeric blends of pheromone, which cases them to be reproductively isolated (Thomas et al, 2003). By shifting onto maize, O. nubilis was able to escape many of its natural enemies and reduce its mortality due to parasitism (Thomas et al, 2003;Pelissie et al, 2010).…”

“…In order to improve ecological pest management, more effort is needed to determining how pest have evolved to utilize novel host plants, and whether these novel adaptations may in turn limit conservation biological control. Insect herbivores appear to adapt to novel hosts and cropping systems more easily than do their natural enemies (Hare, 1990;Gratton and Welter, 1999;Toepfer and Kuhlmann, 2004;Pelissie et al, 2010). By feeding on introduced crops, insect herbivores may adapt to novel physical, chemical, semiochemical, and phenological plant traits.…”