Parasitism by endoparasitoid wasps alters the internal but not the external microbiome in host caterpillars

Background The microbiome of many insects consists of a diverse community of microorganisms that can play critical roles in the functioning and overall health of their hosts. Although the microbial communities of insects have been studied thoroughly over the past decade, little is still known about how biotic interactions affect the microbial community structure in and on the bodies of insects. In insects that are attacked by parasites or parasitoids, it can be expected that the microbiome of the host insect is affected by the presence of these parasitic organisms that develop in close association with their host. In this study, we used high-throughput amplicon sequencing targeting both bacteria and fungi to test the hypothesis that parasitism by the endoparasitoid Cotesia glomerata affected the microbiome of its host Pieris brassicae. Healthy and parasitized caterpillars were collected from both natural populations and a laboratory culture. Results Significant differences in bacterial community structure were found between field-collected caterpillars and laboratory-reared caterpillars, and between the external and the internal microbiome of the caterpillars. Parasitism significantly altered the internal microbiome of caterpillars, but not the external microbiome. The internal microbiome of all parasitized caterpillars and of the parasitoid larvae in the caterpillar hosts was dominated by a Wolbachia strain, which was completely absent in healthy caterpillars, suggesting that the strain was transferred to the caterpillars during oviposition by the parasitoids. Conclusion We conclude that biotic interactions such as parasitism have pronounced effects on the microbiome of an insect host and possibly affect interactions with higher-order insects.

Environmentally acquired chemical camouflage affects Pieris brassicae L. host plant selection and orientation behaviour of a larval parasitoid

Environmentally acquired chemical camouflage is a phenomenon, where a plant growing close to a strong volatile organic compound (VOC) emitter will adsorb and re-emit the VOCs produced by the neighbouring plant. The re-emitted volatile bouquet may resemble more the VOC composition of the neighbour than plant’s own typical odour, and thus act as chemical camouflage against insect detection, potentially simultaneously providing associational resistance towards herbivory. We exposed a pest-sensitive horticultural crop, Brassica oleracea var. italica (broccoli) cv. Lucky, to the volatiles emitted by Rhododendron tomentosum [RT] twigs and assessed the host selection by ovipositing females and larval instars of the major caterpillar pest Pieris brassicae between RT-exposed and control plants. Potential impact of RT exposure on herbivore natural enemies was studied using behavioural tests with a parasitoid wasp Cotesia glomerata. P. brassicae females laid significantly less eggs and egg clusters were fewer on RT-exposed plants at both night-time (6 °C) and daytime (22 °C) temperatures. Larvae preferred leaves from control plants over RT-exposed plants at both temperatures. Preceding RT-exposure did not disturb orientation of parasitoid wasp Cotesia glomerata females towards B. oleracea plants damaged by its host P. brassicae. However, host-damaged control plants were favoured by the parasitoid over RT-exposed, host-damaged plants. Our results suggest that companion plant based chemical camouflage as a mechanism of pest suppression could be developed as an additional tool for the integrated pest management toolbox in agriculture.

Population dynamics and parasitoid complex of Archips rosana (L.) (Lepidoptera: Tortricidae) in Western Turkey

The rose tortrix moth, Archips rosana (L.) (Lepidoptera: Tortricidae), is a pest that causes serious crop losses in apple orchards throughout the world. In this study, the population dynamics of A. rosana and its associated parasitoids were investigated in two provinces of Western Turkey (Denizli and Usak) in 2018 and 2019. A total of 318 egg masses, 300 larvae, and 129 pupae were collected from the survey areas. Although no parasitoids were detected in egg masses, ten parasitoid species belonging to Braconidae, Chalcididae, and Ichneumonidae (Hymenoptera), and Tachinidae (Diptera), were reared from the samples of larvae and pupae. Phytodietus astutus (Gravenhorst) (Ichneumonidae) was the most abundant parasitoid species, with a relative abundance of 35.1%, followed by Itoplectus maculator (Fabricius) (Ichneumonidae) represented by 27% of the recovered parasitoids. Moreover, P. astutus and Scambus inanis (Schrank) (Ichneumonidae) reared from the samples are the first records from Turkey, while Cotesia glomerata (L.) (Braconidae), Exochus sp.(Ichneumonidae), and Nemorilla maculosa (Meigen) (Tachinidae) are the first records from A. rosana. Using pheromone traps in the apple orchards, the first adult of A. rosana was caught on May 24 in Civril (Denizli) and on May 30 in Sivasli (Usak) in 2019

Reproduction and Offspring Sex Ratios Differ Markedly among Closely Related Hyperparasitoids Living in the Same Microhabitats

Closely related species in nature usually exhibit very similar phylogenetically conserved traits, such as reproduction, behavior and development. Here, we compared fecundity schedules, lifetime reproductive success and offspring sex ratios in three congeneric facultative hyperparasitoid wasps that exhibit several overlapping traits and which co-occur in the same small-scale habitats. Gelis agilis, G. proximus and G. hortensis are abundant in meadows and forest edge habitats in the Netherlands. Gelis agilis is asexual (all female), whereas the other two species reproduce sexually. Here they developed on cocoons of the primary parasitoid Cotesia glomerata. When provided with unlimited hosts, lifetime reproductive success was three times higher in G. proximus than in G. agilis with G. hortensis producing intermediate numbers of offspring. All three species depleted their teneral reserves during their lives. Females of G. proximus and G. hortensis lived significantly longer than females of G. agilis. Offspring sex ratios in young G. proximus mothers were female-biased and marginally male-biased in G. hortensis. As mothers aged, however, the ratio of male:female progeny produced rapidly increased until no daughters emerged later in life. Our results reveal significant differences in reproductive traits among the three species despite them co-occurring in the same microhabitats, being very closely related and morphologically similar. The increase in the production of male progeny by Gelis mothers over time suggests a depletion in sperm number or viability with age. This is especially interesting, given that Gelis species are among the least fecund parasitoids thus far studied. It is likely that in the field most Gelis mothers are probably only able to parasitize a few hosts and to maintain the production of female offspring.

БАЙЦААТНЫ ТӨРЛИЙН ТАРИМЛЫН ТАЛБАЙД САРЬСАН ДАЛАВЧИТ ПАРАЗИТ ШАВЬЖ-(Cotesia glomerata L)-ИЙН БИОЛОГИЙН ХАМГААЛЛЫН АЧ ХОЛБОГДОЛЫГ СУДАЛСАН ДҮН

Энэхүү судалгааны үр дүнгээр байцаа тариалсан нутгуудад байцааны төрөл (Brassicaceae), сортууд дээр сармаг манжингийн цагаан эрвээхэйн паразит шавьж (Cotesia glomerata L) шонхор зөгийн гаралт, тархалтыг тооцож үзэхэд эртийн байцаанд паразитойдын хүүхэлдэй 49 ширхэг, дунд оройн болцтой байцаанд 38 ширхэг, хүрэн байцаанд-22 ширхэг тохиолдож байсан бол броколи байцаанд-9 ширхэг тоологдсон нь эзэн шавьж болох сармаг манжингийн цагаан эрвээхэй нь броколи (Brassica olereacia) болон хүрэн байцаа (Brassica olereacia var capitata)-г бага гэмтээж байгаатай холбоотой гэж үзэж байна. Бөөрөнхий байцааны дөрвөн өөр сорт дээр сармаг манжингийн цагаан эрвээхэйн паразит (Cotesia glomerata L)-гийн тархалт, нягтрал, тохиолдоцын төлөв бүх сортын байцаан дээр паразит нь эзэн шавьжаас илт давамгайлж байснаас үзэхэд паразитойд (Cotesia glomerata L) нь сармаг манжингийн цагаан эрвээхэйн популяцийг дарангуйлах хэмжээнд гарч тархаж байгаа нь харагдаж байна. Химийн инсектицид хэрэглэсэн талбайд байцааны хөнөөлтэй зүйл болох сармаг манжингийн цагаан эрвээхэйн нягтрал тооцоот ургамал дээр 711.2-941.4 бодьгаль, харин пестицид хэрэглээгүй талбайд төдийлөн ихсээгүй 15±0.0-36±0.3 бодьгалийн нягтралтай байгаа нь түүний паразитойд (Cotesia glomeratа L) нь энэхүү зүйлийг хөнөөл учруулахаас доогуур түвшинд барьж байгааг илтгэж байна. Үүнээс үзэхэд химийн инсектицид нь ашигтай зүйлийн гаралт, тархалтанд сөрөг нөлөөтэй нь харагдаж байна.

Adequação do hospedeiro e parâmetros relacionados à aptidão de Cotesia glomerata L. (Hymenoptera: Braconidae) em diferentes ínstares de Ascia monuste orseis Godart (Lepidoptera: Pieridae)

RESUMO: O estudo teve por objetivo adequar o ínstar do hospedeiro Ascia monuste orseis ao parasitismo de Cotesia glomerata e avaliar o desempenho do parasitoide. Foram oferecidas às fêmeas de C. glomerata lagartas de 2o, 3o, 4o e 5o ínstares de A. monuste orseis , permitindo-se o parasitismo por duas horas. Subsequentemente, acompanhou-se o desenvolvimento das lagartas que foram alimentadas com seções foliares de couve-manteiga. Foram avaliados: a duração de cada ínstar das lagartas, o peso da pupa com quatro dias de idade e a porcentagem de lagartas parasitadas e de mortalidade. Em relação ao parasitoide, foram avaliados: porcentagem de parasitismo; número de parasitoide por hospedeiro; porcentagem de emergência; razão sexual; peso médio da pupa; número de parasitoide por lagarta; período ovo-pupa (POP); período pupal (PP); período ovo-adulto (POA). Os resultados indicaram que o segundo ínstar do hospedeiro A. monuste oreseis é o mais apropriado para o parasitismo de C. glomerata por proporcionar maior porcentagem de parasitismo e maior número de descendentes por hospedeiro.

Oviposition preference of cabbage white butterflies in the framework of costs and benefits of interspecific herbivore associations

When deciding where to oviposit, herbivorous insects consider: (i) the plant’s value as a food source, (ii) the risks of competing with con- and heterospecific herbivores, and (iii) the risks of parasitism and predation on the host plant. The presence of con- and/or heterospecific competitors would further affect the oviposition preference, because the preceding herbivores induce direct/indirect defences in plants against forthcoming herbivores, and thereby alter oviposition decisions. In previous studies, the abovementioned factors have not been studied in an integrative manner. We performed here a case study of this by assessing the oviposition preferences of a small white butterfly, Pieris rapae , for plants occupied by combinations of conspecific larvae, heterospecific larvae ( Plutella xylostella ), specialist parasitoids of Pi. rapae ( Cotesia glomerata ) and generalist predators (ants). We previously reported that the females showed equal preference for Pl. xylostella -infested and uninfested plants. Here, we showed that Pi. rapae females preferred uninfested plants to conspecific-infested ones, and Pl. xylostella -infested plants to Pi. rapae -infested ones. We discuss these oviposition preferences of Pi. rapae females in the framework of costs and benefits of interspecific herbivore associations from the above point of view.