Living with the enemy: parasites and pathogens of the ladybird Harmonia axyridis

Abstract

Harmonia axyridis is an invasive alien predator in many countries across the world. The rapid establishment and spread of this species is of concern because of the threat it poses to biodiversity as a generalist predator. Understanding the mechanisms that contribute to the success of this species as an invader is not only intriguing but also critical to our understanding of the processes governing such invasions. The enemy release hypothesis (ERH) could explain the rapid population growth of many invasive alien species. However, empirical evidence in support of the ERH is lacking. An alternative hypothesis that could explain rapid population growth is evolution of increased competitive ability (EICA).Here we provide an overview of the parasites and pathogens of coccinellids with a particular focus on H. axyridis as a host. We examine the differential susceptibility of host species and highlight the resilience of H. axyridis in comparison to other coccinellids. We recognise the paucity and limitations of available information and suggest that studies, within a life-table framework, comparing life history traits of H. axyridis in both the native and introduced ranges are necessary. We predict that H. axyridis could benefit from both enemy release and EICA within the introduced range but require further empirical evidence.

Harmonia axyridis (Coleoptera: Coccinellidae) as a host of the parasitic fungus Hesperomyces virescens (Ascomycota: Laboulbeniales, Laboulbeniaceae): A case report and short review

“…The association between Harmonia axyridis and Hesperomyces virescens is an example of the latter, less frequent, process. The case described above can be included with an increasing body of evidence that the invasive populations of the harlequin ladybird are not only susceptible to some native parasites such as H. virescens, the mite Coccipolipus hippodamiae (McDaniel & Morrill) (Rhule et al, 2010;Riddick, 2010) and allantonematid nematodes (Harding et al, 2011;Roy et al, 2011b;Poinar & Steenberg, 2012), but also contribute to their dispersal, increase in prevalence and intensity of infection.…”

Hesperomyces virescens (Fungi, Ascomycota, Laboulbeniales) attacking Harmonia axyridis (Coleoptera, Coccinellidae) in its native range

“…Roy et al [10] suggest that H. virescens is probably native to North America, referring to the fact that Thaxter [33] first found it in the USA on C. stigma and Hippodamia convergens Guérin-Méneville, 1842, both native to North America [34]; soon more recordings from new localities extended the distribution of H. virescens to South America, Asia, and Oceania [35,36]. The (historical) records for China of H. virescens parasitizing H. axyridis in this study give rise to the suggestion that H. virescens is a global species.…”

“…This combination between genetically diverse populations from the native range may have facilitated the success of H. axyridis in North America, and consequently its subsequent expansion. It has been suggested that with the rapid expansion of H. axyridis also H. virescens will continue to spread globally [10] and threaten native, noninvasive Asian populations of H. axyridis [11].…”

“…The enemy release hypothesis predicts that an invasive species in its new environment will experience a decrease in regulation by natural enemies, resulting in a competitive advantage for the alien species over native species [7,8]. While it has been suggested [9] that there is no support of natural enemies exerting regulatory effects on coccinellid populations, a recent study provides an overview of parasites and pathogens with focus on the resilience of H. axyridis compared to other Coccinellidae [10].…”

“…(Ascomycota, Laboulbeniales). Previous work states that H. virescens does not attack H. axyridis in its native range [10,11]. We explore evidence available for assessing the (historical) distribution of H. virescens.…”