The Enemy Release Hypothesis (ERH) has been a factor influencing the establishment of some exotic species worldwide. We tested if the ERH could be influencing populations of the exotic predator Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) in Brazil. During two years, three local predatory coccinellid species and Harmonia axyridis were sampled in Brassica oleracea in six organic farms in the midwest of the country. Parasitoids were detected by rearing (emerged) and qPCR Melting Curve Analysis (unemerged). Host density-dependence and spillovers were used to evaluate coccinellid population effects of parasitism. Six parasitoid species were found, including two new records for Brazil. Although Harmonia axyridis harbored fewer parasitoid species, parasitism was not lower and parasitoid density-dependence was not weaker on it compared to the local species. Spillovers among hosts occurred both onto Harmonia axyridis and from it. The ERH was rejected for these parasitoids and, therefore, it did not contribute to the invasiveness of Harmonia axyridis in Brazil.
Bibliographical noteFunding Information:
We thank J.R. Pujol Luz (Universidade de Brasília, Brazil) for identification for Strongygaster triangulifera, and all the farmers that allowed the host samplings in 2017 and 2018. We also thank Iane P. Ferreira, Karina S. Kubota and Stephanie S. Ribeiro for help in sampling hosts. We also thank Embrapa for the financial support by the grant number SEG 12.13.12.005.00.00 and CAPES Print and the Graduate Program from the Department of Ecology, Universidade de Brasília, Brazil, for the fellowship to DAA.
- Host-density dependence
- Parasitoid spillover