Mortality of native and invasive ladybirds co-infected by ectoparasitic and entomopathogenic fungi

Abstract

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.

Ectoparasitic fungi of Myrmica ants alter the success of parasitic butterflies

“…Further experiments focussing on host fitness would be necessary to examine this aspect of the interactions. Theoretical models 1,2,7 , greenhouse and laboratory experiments 3,5 , and examples from biological control 4,6 suggest that synergistic or additive virulence effects are most likely 58,59 , so the possibility of a conditional 60 antagonistic effect, as outlined above, is intriguing. Such effects are likely to be more common than hitherto documented 61 ; for example, such a conditional effect has recently been proposed for a microsporidian parasite of Daphnia 62 .…”

“…Pre-pupal caterpillars of P. alcon were somewhat larger in nests infected with R. wasmannii than those found in uninfected nests. Based on these results it seems that R. wasmannii infection of M. scabrinodis affects the survival and development of P. alcon caterpillars, suggesting competition between these two ant parasites.Organisms are often exploited by multiple parasites in nature, but this is rarely highlighted in ecological studies [1][2][3] . From the point of view of the host, co-infecting parasites may have synergistic, additive, or antagonistic effects on fitness 1,4,5 .…”

“…Organisms are often exploited by multiple parasites in nature, but this is rarely highlighted in ecological studies [1][2][3] . From the point of view of the host, co-infecting parasites may have synergistic, additive, or antagonistic effects on fitness 1,4,5 .…”

On the Fly: Tritrophic Associations of Bats, Bat Flies, and Fungi

“…The effects of Laboulbeniales on their hosts have not been well-studied. Laboratory bioassays have only been performed for one species; Hesperomyces virescens increases the mortality of native and invasive ladybirds [ 89 ]. But how do Laboulbeniales associated with bat flies affect their hosts?…”

Nondetrimental impact of two concomitant entomopathogenic fungi on life history parameters of a generalist predator, Coccinella septempunctata (Coleoptera: Coccinellidae)

“…Due to the high importance of coccinellid beetles in aphid biological control programs, it is necessary to determine the impact of other biological agents such as EPFs on these generalist predators. Although studies are available on the interaction of EPFs with other biological control agents 34 , 35 , their effect on the life table and demographic parameters on the coccinellids is limited. Life table is an important tool to study population ecology and summarize the survival and reproductive potential of insect populations on different hosts 36 – 38 .…”