Mortality of native and invasive ladybirds co-infected by ectoparasitic and entomopathogenic fungi
Danny Haelewaters,
Thomas Hiller,
Emily A. Kemp,
Paul S. van Wielink,
David I. Shapiro-Ilan,
M. Catherine Aime,
Oldřich Nedvěd,
Donald H. Pfister,
Ted E. Cottrell
Affiliations
Danny Haelewaters
Farlow Reference Library and Herbarium of Cryptogamic Botany, Harvard University, Cambridge, MA, United States of America
Thomas Hiller
Institute of Evolutionary Ecology and Conservation Genomics, University of Ulm, Ulm, Germany
Emily A. Kemp
Agricultural Research Service, Southeastern Fruit and Tree Nut Research Laboratory, United States Department of Agriculture, Byron, GA, United States of America
Paul S. van Wielink
Natuurmuseum Brabant, Tilburg, The Netherlands
David I. Shapiro-Ilan
Agricultural Research Service, Southeastern Fruit and Tree Nut Research Laboratory, United States Department of Agriculture, Byron, GA, United States of America
M. Catherine Aime
Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN, United States of America
Oldřich Nedvěd
Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic
Donald H. Pfister
Farlow Reference Library and Herbarium of Cryptogamic Botany, Harvard University, Cambridge, MA, United States of America
Ted E. Cottrell
Agricultural Research Service, Southeastern Fruit and Tree Nut Research Laboratory, United States Department of Agriculture, Byron, GA, United States of America
Harmonia axyridis is an invasive alien ladybird in North America and Europe. Studies show that multiple natural enemies are using Ha. axyridis as a new host. However, thus far, no research has been undertaken to study the effects of simultaneous infection by multiple natural enemies on Ha. axyridis. We hypothesized that high thallus densities of the ectoparasitic fungus Hesperomyces virescens on a ladybird weaken the host’s defenses, thereby making it more susceptible to infection by other natural enemies. We examined mortality of the North American-native Olla v-nigrum and Ha. axyridis co-infected with He. virescens and an entomopathogenic fungus—either Beauveria bassiana or Metarhizium brunneum. Laboratory assays revealed that He. virescens-infected O. v-nigrum individuals are more susceptible to entomopathogenic fungi, but Ha. axyridis does not suffer the same effects. This is in line with the enemy release hypothesis, which predicts that invasive alien species in new geographic areas experience reduced regulatory effects from natural enemies compared to native species. Considering our results, we can ask how He. virescens affects survival when confronted by other pathogens that previously had little impact on Ha. axyridis.
