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. 19 Studies show that multiple natural enemies are using Ha. axyridis as a new host. However, thus 20 far, no research has been undertaken to study the effects of simultaneous infections of multiple 21 natural enemies on Ha. axyridis. We hypothesized that high thallus densities of the ectoparasitic 22 fungus Hesperomyces virescens on a ladybird weaken the host's defenses, thereby making it 23 2 more susceptible to infection by other natural enemies. We examined mortality of the North 24 American-native Olla v-nigrum and Ha. axyridis co-infected with He. virescens and an 25 entomopathogenic fungus-either Beauveria bassiana or Metarhizium anisopliae. Laboratory 26 assays revealed that He. virescens-infected O. v-nigrum individuals are more susceptible to 27 entomopathogenic fungi, but Ha. axyridis does not suffer the same effects. This is in line with 28 the enemy release hypothesis, which predicts that invasive alien species in new geographic areas 29 experience reduced regulatory effects from natural enemies compared to native species. 30 Considering our results, we can ask how He. virescens affects survival when confronted by other 31 pathogens that previously had little impact on Ha. axyridis. 32 33In nature and in agricultural ecosystems, hosts may be exploited by more than one natural 34 enemy. These organisms interact with each other and with their hosts 1 . These complex 35 interactions shape the population structure and dynamics of all organisms in the system. Natural 36 enemies also compete with one another, and the impact on the host can be either synergistic, 37 additive, or antagonistic 2 . These interactions can be manifested in various aspects of host fitness 38 or mortality. For example, biological control of Drosophila suzukii (Diptera, Drosophilidae), an 39 important pest of fruit and berry crops, can be improved by treatments combining multiple 40 natural enemies, which have an additive effect 3 . At the same time, dual infections (even if 41 causing an increase in host mortality) may be deleterious to one or both pathogens in terms of 42 pathogen growth, fecundity, or other fitness parameters.43 44Harmonia axyridis (Coleoptera, Coccinellidae), native to eastern Asia, has rapidly increased its 45 global range and is now present on all continents except Antarctica 4,5,6 . Even though it has 46 repeatedly been introduced for its beneficial properties as a biological control agent against aphid 47 pests, its negative effects on native ladybird communities in invaded areas 7,8,9 and on food 48 production 7 have raised serious concerns since the early 2000s 4 . It is now a model organism for 49 studying invasive alien species 10,11 and it has been listed in Europe as "one of the worst" invasive 50 species 12 . Harmonia axyridis is often reported as host to several natural enemies. These include 51 parasites (Hesperomyces virescens, Coccipolipus hippodamiae, Parasitylenchus bifurcatus), 52 parasitoids (phorid and tachinid...

Inter-Parasitic Interactions in Myrmica Ants: Ectoparasitic Fungus Affecting the Success of Socially Parasitic Caterpillars

“…1, Supplementary Video S1) is one of the most widespread ectoparasitic 57 Laboulbeniales fungal species in Europe, infecting ten Myrmica species and some of their arthropod associates from Turkey to Portugal [58][59][60][61] . Several effects of Laboulbeniales fungi on their hosts are known, which are primarily negative 3,10,[25][26][27][28]62 but can also be indirectly positive 63 . Research in recent years has made R. wasmannii one of the best known ant-parasitic Laboulbeniales species.…”

“…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 tness-as a consequence, these interactions may be exploited for biological control purposes 1,4,5 .…”