Predators and parasitoids of the harlequin ladybird, Harmonia axyridis, in its native range and invaded areas

GREGARINA LUTESCENS N. SP. INFECTING THE HARLEQUIN LADYBIRD HARMONIA AXYRIDIS (COLEOPTERA: COCCINELLIDAE)

Gregarina lutescens n. sp. is described from the alimentary canal of the harlequin ladybird or multicolored Asian lady beetle, Harmonia axyridis (Coleoptera: Coccinellidae) collected from prairie fleabane, Erigeron strigosus, at Peru State College, Peru, Nemaha Co., Nebraska. Our specimens differ from all 11 known species of Gregarina infecting coccinellid beetles worldwide by differences in size and relative shape, color, and association structure. Gregarina lutescens n. sp. is smaller than 7 known species infecting coccinellid beetles but larger than the other 4 known species based on confidence interval exclusion of means. Our specimens are unique among known species of interest in their quince-yellow cytoplasm and precocious but ephemeral serial associations of up to 5 satellites. Nucleotide sequence (18S) phylogenetic analyses place the new species basal to a member of an internal clade of Gregarina that comprises gregarines parasitizing chrysomelid beetles. Phylogenetically, the analysis recovered 3 major lineages within the gregarines, representing the superfamilies Gregarinoidea, Stenophoroidea, and Stylocephaloidea and indicating the propensity of gregarines to track host lineages and environments through evolutionary time. These findings confirm the polyphyletic nature of Gregarina, which currently comprises over 300 described species, only a handful of which have documented genetic sequences suitable for phylogenetic analysis. Recollection, redescription, and molecular clarification of gregarine species infecting coccinellids would likely result in identification of a unique clade that would be an excellent system for studying the effect of intraguild host competition on parasite diversification and community structure. Ecologically, patterns of prevalence in this study indicate that G. lutescens reproduces primarily in larval hosts but depends on infections in adult beetles to overwinter, reflecting the differential vagility and frost tolerance of larval and adult host life cycle stages.

Invasive brown widow spiders avoid parasitism despite high densities

Invasive species are sometimes less susceptible to natural enemies compared to native species, but the mechanism is often unclear. Here we tested two potential mechanisms for lower parasitism of invasive species: density-dependent parasitism and preference for human-dominated habitats. We investigated how variation in host density and habitat type affect egg sac parasitism in two widow spider species (family Theridiidae). We compared parasitism on the egg sac of the brown widow, Latrodectus geometricus, an urban invasive species, and the white widow, Latrodectus pallidus, a species native to Israel. To investigate variation in host and parasitoid density, we measured nearest-neighbor distance between spider webs and parasitism rates in 16 sites, and in a single site monthly throughout a year. In L. pallidus, denser sites were more heavily parasitized (up to 55%) and parasitism rate increased with population density throughout the season. Extremely dense L. geometricus populations, however, had very low rates of parasitism (0-5%). We then conducted an egg sac transplant experiment in human-dominated and natural habitats. We found no parasitism of either species in the human-dominated habitat, compared to 30% parasitism of both species in the natural habitat. In addition, we found evidence for higher predation of L. pallidus than of L. geometricus egg sacs, particularly in the natural habitat. These combined results suggest that the human-dominated habitats inhabited by L. geometricus have a lower abundance of predators and parasites. We conclude that lower parasitism and predation in human-dominated habitats could contribute to the invasion success of L. geometricus.

Infection patterns of Harmonia axyridis (Coleoptera: Coccinellidae) by ectoparasitic microfungi and endosymbiotic bacteria

The invasive alien ladybird Harmonia axyridis (Coleoptera: Coccinellidae) hosts a wide range of natural enemies. Many observations have been done in nature but experimental studies of interactions of multiple enemies on Ha. axyridis are rare. In light of this knowledge gap, we tested whether the host phenotype and presence of bacterial endosymbionts Spiroplasma and Wolbachia affected parasitism of Ha. axyridis by the ectoparasitic fungus Hesperomyces harmoniae (Ascomycota: Laboulbeniales). We collected 379 Ha. axyridis in the Czech Republic, processed specimens, including screening for He. harmoniae and a molecular assessment for bacteria, and calculated fecundity and hatchability of females. We found that high hatchability rate (71 %) was conditioned by high fecundity (20 eggs daily or more). The average parasite prevalence of He. harmoniae was 53 %, while the infection rate of Spiroplasma was 73 % in ladybirds that survived in winter conditions. Wolbachia was only present in 2 % of the analyzed ladybirds. Infection by either He. harmoniae or Spiroplasma did not differ among host color morphs. In the novemdecimsignata morph, younger individuals (with orange elytra) were more heavily parasitized compared to old ones (with red elytra). Fecundity and hatchability rate of females were unaffected by infection with either He. harmoniae or Spiroplasma. However, female ladybirds co-infected with He. harmoniae and Spiroplasma had a significantly lower fecundity and hatchability compared to females with only one or no symbiont.

The Biology and Ecology of Parasitoid Wasps of Predatory Arthropods

Parasitoid wasps are important components of insect food chains and have played a central role in biological control programs for over a century. Although the vast majority of parasitoids exploit insect herbivores as hosts, others parasitize predatory insects and arthropods, such as ladybird beetles, hoverflies, lacewings, ground beetles, and spiders, or are hyperparasitoids. Much of the research on the biology and ecology of parasitoids of predators has focused on ladybird beetles, whose parasitoids may interfere with the control of insect pests like aphids by reducing ladybird abundance. Alternatively, parasitoids of the invasive ladybird Harmonia axyridis may reduce its harmful impact on native ladybird populations. Different life stages of predatory insects and spiders are susceptible to parasitism to different degrees. Many parasitoids of predators exhibit intricate physiological interrelationships with their hosts, adaptively manipulating host behavior, biology, and ecology in ways that increase parasitoid survival and fitness.

Fungal ectoparasites increase winter mortality of ladybird hosts despite limited effects on their immune system

Winter represents a challenging period for insects inhabiting temperate regions. A plethora of studies have investigated how environmental conditions such as temperature affect insect overwintering success. However, only a few studies have focused on biotic factors and the mechanisms affecting the overwintering performance of insects. Here, we investigated the effects of the parasitic fungus Hesperomyces virescens on the overwintering performance and immune system functioning of the invasive ladybird Harmonia axyridis. Winter survival was significantly lower for infected than for uninfected ladybirds. Body mass loss during overwintering tends to be higher for infected individuals compared to uninfected ones and for larger ladybirds. In addition, parasitic infection reduced post-winter longevity without food in male but not female ladybirds. Total haemocyte and protein concentration as well as antimicrobial activity against Escherichia coli significantly decreased during ladybird overwintering. However, haemolymph parameters were only poorly affected by Hesperomyces infection, with the exception of antimicrobial activity against E. coli that tended to be higher in infected ladybirds. Interestingly, none of the pre-winter haemolymph parameters were good predictors of ladybird winter survival. Overall, our results indicate that energy exhaustion unrelated to immune system challenge is the most probable explanation for increased overwintering mortality in infected ladybirds.

Genome of the parasitoid wasp Dinocampus coccinellae reveals extensive duplications, accelerated evolution, and independent origins of thelytokous parthenogeny and solitary behavior

Dinocampus coccinellae (Hymenoptera: Braconidae) is a generalist parasitoid wasp that parasitizes >50 species of predatory lady beetles (Coleoptera: Coccinellidae), with thelytokous parthenogeny as its primary mode of reproduction. Here, we present the first high-quality genome of D. coccinellae using a combination of short- and long-read sequencing technologies, followed by assembly and scaffolding of chromosomal segments using Chicago + HiC technologies. We also present a first-pass ab initio and a reference-based genome annotation and resolve timings of divergence and evolution of (1) solitary behavior vs eusociality, (2) arrhenotokous vs thelytokous parthenogenesis, and (3) rates of gene loss and gain among Hymenopteran lineages. Our study finds (1) at least 2 independent origins of eusociality and solitary behavior among Hymenoptera, (2) 2 independent origins of thelytokous parthenogenesis from ancestral arrhenotoky, and (3) accelerated rates of gene duplications, loss, and gain along the lineages leading to D. coccinellae. Our work both affirms the ancient divergence of Braconid wasps from ancestral Hymenopterans and accelerated rates of evolution in response to adaptations to novel hosts, including polyDNA viral coevolution.

Double Infections of the Invasive Ladybird Harmonia axyridis

The dramatic spread of invasive alien species over the past century is considered to be an important threat to ecosystems worldwide. The harlequin ladybird, Harmonia axyridis, from eastern Asia, is considered to be one of the most invasive species. Originally introduced across the world as a biological control agent against crop pests owing to its voracious appetite and hardiness, those same qualities have made H. axyridis an invader that is difficult to eradicate. Harmonia axyridis has proven resilient against a variety of pathogens that have negative effects on other coccinellids. However, little research has examined the effects of simultaneous infections of multiple natural enemies on H. axyridis. Here we present the available information on such double infections on H. axyridis, and discuss further research directions in this area.

Basic Studies Aiming at Orius minutus (Hemiptera: Anthocoridae) Mass-Rearing

Simple Summary

The rapid growth of the biocontrol market is increasing the research into the usefulness of native natural enemies. For the commercial use of native natural enemies, economical mass-rearing technology must be developed. This study was conducted to establish a mass-rearing technique for improving the usability of Orius minutus in Korea. This species uses plants for moisture intake, nutritional supplementation, and oviposition substrates. However, the use of plants in mass production systems significantly increases the cost of production. Eggs of stored grain insect pests used as food in rearing Orius spp., are the most nutritionally balanced food source, but their high market price necessitates the selection of an economical food source to replace them. In this study, Ephestia cautella eggs and iron-coated brine shrimp eggs were selected as diet, and cork sheets were selected as an artificial oviposition substrate to obtain basic data for establishing a plant-free rearing system. The plant-free model developed in our study can reduce rearing costs by 70.5% compared to the conventional mass-rearing model.

Abstract

This study presented biological and economic data for the mass-rearing of Orius minutus in Korea. Simplifying the mass-rearing process through an alternative diet and an artificial oviposition substrate is a prerequisite for enhancing the usability of this insect as a biological control agent. We compare the hatch rate of O. minutus eggs deposited on a plant substrate with that of eggs deposited on two artificial substrates, cork sheets and rubber. The results indicate that cork sheet is the most cost-effective artificial oviposition substrate for the mass-rearing of O. minutus. We also examine five feeding treatments that included two types of brine shrimp eggs and eggs of Ephestia cautella to compare the number of eggs laid in the fifth generation. We found no significant difference between the two treatment groups; 61.3 eggs were laid in the treatment group fed iron-coated brine shrimp and moth eggs, and 67.4 eggs were laid in the control group. The plant-free model developed in our study can reduce rearing costs by 70.5% compared to the conventional mass-rearing model.

<i>HARMONIA AXYRIDIS</i> (PALLAS, 1773) (COLEOPTERA: COCCINELLIDAE) IN MOSCOW CITY AND YALTA CITY: ITS COMPETITION WITH NATIVE SPECIES OF COCCINELLIDS AND THE INFLUENCE OF PARASITOIDS ON ITS NUMBER

The Asian ladybird Harmonia axyridis is an invasive species that is rapidly spreading around the world. Occupying new territories, H. axyridis often causes a decrease in the biodiversity of native species of coccinellids, competing with them for food resources. A comparison of H. axyridis with six species of ladybirds was made in terms of the ratio of the number of individuals and the degree of infestation with parasitoids. In Moscow city, the most widespread species of ladybirds was Adalia bipunctata (67.1%), H. axyridis ranks second (16.5%). The total infestation of H. axyridis pupae with parasitoids is 1.8% in Moscow city and 12.2% in Yalta city. Infestation with parasitoids of other ladybird species in Moscow city is much higher: from 11.0% to 36.4%. Thus, parasitoids effectively regulate the number of native ladybird species, but have an insignificant effect on the number of the invasive species H. axyridis .

Fungi of entomopathogenic potential in Chytridiomycota and Blastocladiomycota, and in fungal allies of the Oomycota and Microsporidia

The relationship between entomopathogenic fungi and their insect hosts is a classic example of the co-evolutionary arms race between pathogen and target host. The present review describes the entomopathogenic potential of Chytridiomycota and Blastocladiomycota fungi, and two groups of fungal allies: Oomycota and Microsporidia. The Oomycota (water moulds) are considered as a model biological control agent of mosquito larvae. Due to their shared ecological and morphological similarities, they had long been considered a part of the fungal kingdom; however, phylogenetic studies have since placed this group within the Straminipila. The Microsporidia are parasites of economically-important insects, including grasshoppers, lady beetles, bumblebees, colorado potato beetles and honeybees. They have been found to display some fungal characteristics, and phylogenetic studies suggest that they are related to fungi, either as a basal branch or sister group. The Blastocladiomycota and Chytridiomycota, named the lower fungi, historically were described together; however, molecular phylogenetic and ultrastructural research has classified them in their own phylum. They are considered parasites of ants, and of the larval stages of black flies, mosquitoes and scale insects.

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

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.

Biogeographical comparison of terrestrial invertebrates and trophic feeding guilds in the native and invasive ranges of Carpobrotus edulis

Plant invasions impact on biodiversity by altering the composition of native communities by disrupting taxonomic and functional diversity. Non-native plants are often released from their natural enemies, which might result in a reduction of the attack of primary consumers. However, they can also be exposed to the attack of new herbivores that they might not be able to tolerate. Hence, invertebrate communities can be influenced by invasive non-native plants, which in turn modify interactions and change environmental conditions. In this study, we examined the compositional and trophic diversity of invertebrate species, comparing ecosystems with and without the plant species Carpobrotus edulis in coastal areas in its native (South Africa) and introduced (Iberian Peninsula) ranges. Results show that C. edulis has a clear impact on invertebrate communities in its non-native range, reducing their abundance in invaded areas, and particularly affecting certain trophic groups. Invasive C. edulis also alters the invertebrate diversity by not only reducing abundance but also by altering species composition. Overall, the physical dominance of C. edulis modifies the co-occurrence of invertebrate assemblages, reducing the number of trophic groups and leading to substantial effects on primary consumers. Results suggest that the lack of natural enemies might be an important driver of the expansion of C. edulis in its introduced range. Further work is needed to examine long-term changes caused by non-native plants on invertebrate assemblages and the subsequent modification of biological interactions.

Fifty Shades of the Harlequin Ladybird and a Sexually Transmitted Fungus

The ectoparasitic fungus Hesperomyces virescens was studied on its invasive host, the harlequin ladybird Harmonia axyridis, in the Czech Republic. A primary aim was to examine the relationship between fungal infection and elytral coloration of the ladybird. Furthermore, the role of host sex and mating status of females were analyzed. Beetles (n = 1,102) were sampled during autumn migration, and then sexed, weighed, and screened for infection. Females were dissected for detection of sperm in their spermathecae. Ladybirds were sorted according to color form and absorbance spectrophotometry was used to quantify carotenoid contents in their elytra. In individuals of the nonmelanic succinea form, the degree of melanization was measured using digital photographs and putative age groups were estimated based on background color of elytra. Sexual differences in infection patterns indicated transmission during copulation: males were infected mostly on elytra and venter, and females had infection almost exclusively on elytra. Mated females had higher infection rate than virgins. There was no influence of genetic color form on the fungal infection. Putative age groups (visual sorting to yellow, orange, and red) correlated with fungal infection. Infected individuals had elevated elytral carotenoid levels in comparison to uninfected individuals, which could be explained by host age. Infection-free succinea beetles were extensively melanized because they emerged later in the season at lower temperatures which induced melanization. Overall, we highlight that H. axyridis is a multivoltine species whose age, if not taken into account in ecophysiological studies, might present a considerable confounding factor.

Steatoda nobilis, a false widow on the rise: a synthesis of past and current distribution trends

The Noble False Widow, Steatodanobilis (Thorell, 1875) (Araneae, Theridiidae), is, due to its relatively large size and potential medical importance, one of the most notable invasive spider species worldwide. Probably originating from the Canary Islands and Madeira, the species is well established in Western Europe and large parts of the Mediterranean area and has spread recently into California and South America, while Central European populations were not known until 2011.

We report on long-time observations that reveal that at least two flourishing populations in Germany (Cologne) have been present for over five years, while in Ecuador one population has been observed between 2014 and 2018 and several other records were made in other parts of the country. Data obtained from the British Spider Recording Scheme demonstrate that the species moved significantly northwards since the report of the first populations in the very South of England, after several decades of relative stasis. The sudden northward expansion highly correlates with a massive rise in press coverage of the species.

In the Americas, S.nobilis is currently known from four countries (USA, Chile, Ecuador, Colombia), and available DNA barcoding data obtained for specimens from this area suggest that multiple introductions occurred within each country. Using ecological niche modeling, we identified suitable climate regions for the species and discuss possible reasons for its current spread. We propose that seaside cities and villages with a temperate oceanic or Mediterranean climate are especially favourable potential habitats for S.nobilis and will face the highest colonization pressure in the future, while tropical upland regions with temperate climates are also vulnerable to invasion by S.nobilis.

Coinvasion by the ladybird Harmonia axyridis (Coleoptera: Coccinellidae) and its parasites, Hesperomyces virescens (Ascomycota: Laboulbeniales) and Parasitylenchus bifurcatus (Nematoda: Tylenchida, Allantonematidae), in the Caucasus

The study of parasites in recently established populations of invasive species can shed light on the sources of invasion and possible indirect interactions between the alien species and native ones. We studied parasites of the global invader Harmonia axyridis (Coleoptera: Coccinellidae) in the Caucasus. In 2012, the first established population of Ha. axyridis was recorded in the Caucasus in Sochi (south of European Russia, Black Sea coast). By 2018, the ladybird had spread to a vast area: Armenia, Georgia and south Russia (Adygea, the Krasnodar territory, the Stavropol territory, Dagestan, Kabardino-Balkaria and North Ossetia). The examination of 213 adults collected in Sochi in 2018 showed that 53% were infested with Hesperomyces virescens fungi (Ascomycota: Laboulbeniales) and that 8% were infested with Parasitylenchus bifurcatus nematodes (Nematoda: Tylenchida, Allantonematidae). The examined Ha. axyridis specimens were free of the parasitic mite Coccipolipus hippodamiae. An analysis of the phylogenetic relationships of P. bifurcatus based on 18S rDNA confirmed the morphological identification of this species. Hesperomyces virescens and P. bifurcatus were first recorded in the Caucasus and Russia, although they are rather widespread in Europe. This likely indicates that they appeared as a result of coinvasion with their host because the populations of Ha. axyridis, He. virescens and P. bifurcatus in the Caucasus are isolated from the main parts of the ranges of these species in Europe. The nearest localities of Ha. axyridis is on another shore of the Black Sea, and the nearest localities of He. virescens and P. bifurcatus are more than 1000 km from the Caucasus. It is impossible to determine whether the first founders of the Caucasian population were infested with the parasites or whether the parasites were introduced by specimens of Ha. axyridis that arrived later from Europe. Harmonia axyridis was released in the region for pest control, but laboratory cultures are always free of He. virescens and P. bifurcatus. Therefore, the detection of He. virescens and P. bifurcatus indicates that the population of Ha. axyridis in the Caucasus could not have derived exclusively from released specimens. We did not find He. virescens on 400 specimens of 29 other ladybird species collected from the same localities as Ha. axyridis in the Caucasus. No reliable correlation between infestation by He. virescens and that by P. bifurcatus has been found. In addition to these two parasites, an unidentified species of the order Mermithida was recorded. This is the first documented case of Ha. axyridis infestation by a parasitic nematode of this order in nature.

The evolution of chemical defenses along invasion routes: Harmonia axyridis Pallas (Coccinellidae: Coleoptera) as a case study

The evolution of increased competitive ability (EICA) hypothesis (Blossey & Nötzold, 1995) postulates that escaping from coevolved enemies increases invaders fitness by energy reallocation from defenses and immunity to growth and reproduction. In this context, we evaluated the evidence of evolutionary change in invasive populations of Harmonia axyridis Pallas (Coccinellidae: Coleoptera). We measured egg defenses-cocktail of hydrocarbons on the egg's surface flagging egg toxicity and the concentration of the main alkaloid harmonine-in individuals from three populations along the invasion route (Japan: native, United States: introduced more than 30 years ago, South Africa: introduced in the early 2000s) in a common garden experiment. Our results support the EICA hypothesis: We found changes along the invasion route in the profiles of the hydrocarbons coating the eggs' surface and a decrease in the concentration of harmonine in eggs from the most recent invasive South African population compared to the long established in the United States and the native Japanese ones.