Browsing by Subject "parasitoid"

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  • Caterpillar Rearing Group (CRG), LepSoc Africa; Staude, Hermann; MacLean, Marion; Mecenero, Silvia; Pretorius, Rudolph J.; Oberprieler, Rolf G.; van Noort, Simon; Sharp, Allison; Sharp, Ian; Balona, Julio; Bradley, Suncana; Brink, Magriet; Morton, Andrew S.; Bodha, Magda J.; Collins, Steve C.; Grobler, Quartus; Edge, David A.; Williams, Mark C.; Sihvonen, Pasi (2020)
    We present an overview of the known host associations of larval Lepidoptera for southern Africa, based on a database of 11 628 rearings, including all Caterpillar Rearing Group (CRG) records and other published records. Rearings per Lepidoptera family show some bias in the rearing effort towards the more conspicuous families, ectophagous groups and non-detritus-feeders but in general follow species diversity. Recorded Lepidoptera host associations per host family for southern Africa are shown. Data analyses revealed the following general trends: of the 20 most reared species 13 are polyphagous; Fabaceae are the most utilised plant family with 2 122 associations, followed by Asteraceae (600), Malvaceae (564) and Anacardiaceae (476); 98.8 % of hosts are vascular plants; and of the 19 most utilised host species 18 are common trees or shrubs. We discuss possible reasons behind these trends, particularly the high utilisation of Fabaceae and the widespread use of trees and shrubs as hosts. We compare recorded host species numbers with species diversity for the 19 most recorded host families and discuss possible reasons for the low utilisation of four plant families with an exceptionally low percentage of Lepidoptera host species / plant host species diversity. All Lepidoptera families for which more than 100 rearings have been recorded (21 families) utilise one (or two in the case of Pyralidae, Nolidae and Hesperiidae) plant family exponentially more than any of the other families, with resulting histograms forming hyperbolic curves, as are typical of distributions of taxonomic assemblages in nature. We calculate an exponential factor to quantify this phenomenon and show that for all 21 Lepidoptera families one host family is utilised 6–33 times more than the average use of other host families. In this paper, the larvae and adults of 953 African, mostly South African, Lepidoptera species reared by the CRG between January 2016 and June 2019 are illustrated together with pertinent host information. 119 Lepidoptera-parasitoid associations are reported, comprising seven hymenopteran families and one dipteran family. With the current data release, larval host association records are now available for 2 826 Lepidoptera species in the southern African subregion, covering about 25 % of the described fauna.
  • Miller, Kirsten E.; Aguilera, Guillermo; Bommarco, Riccardo; Roslin, Tomas (2021)
    Arthropod communities dwelling in adjacent habitats are able to impact one another via shared natural enemies. In agricultural landscapes, drastic differences in resource availability between crop and non-crop habitats cause variation in insect herbivore densities over short distances, potentially driving inter-habitat effects. Moreover, the composition of the landscape in which the habitats are embedded likely affects realised attack rates from natural enemies via impacts on local arthropod community structure. Here, we examine indirect effects between herbivore species within and between habitat types by calculating the potential for apparent competition between multiple populations. Firstly, we aim to determine how disparities in resource availability impact the strength of the potential for apparent competition occurring between habitats, secondly to examine the impact of landscape composition upon these effects, and finally to couch these observations in reality by investigating the link between the potential for apparent competition and realised attack rates. We used DNA metabarcoding to characterise host-parasitoid interactions within two habitat types (with divergent nutrient inputs) at 11 locations with variable landscape composition within an agroecosystem context. We then used these interaction networks to estimate the potential for apparent competition between each host pair and to compare expected versus realised attack rates across the system. Shared natural enemies were found to structure host herbivore communities within and across habitat boundaries. The size of this effect was related to the resource availability of habitats, such that the habitat with high nutrient input exerted a stronger effect. The overall potential for apparent competition declined with increasing land-use intensity in the surrounding landscape and exhibited a discernible impact on realised attack rates upon herbivore species. Thus, our results suggest that increasing the proportion of perennial habitat in agroecosystems could increase the prevalence of indirect effects such as apparent competition among insect herbivore communities, potentially leading to enhanced population regulation via increased attack rates from natural enemies like parasitoid wasps.
  • Paukkunen, Juho; Pöyry, Juha; Kuussaari, Mikko (2018)
    1. Kleptoparasitic and parasitoid insects are expected to be particularly sensitive to changes in habitat availability due to their high trophic position and small population sizes compared with their hosts, but there are only few quantitative studies on their population changes. 2. Here, we studied the distribution and abundance of 48 kleptoparasitic and parasitoid species of cuckoo wasps (Chrysididae) and eight selected host species recorded in Finland from 1840 to 2015 based on an extensive survey of entomological collections. Population trends were assessed by studying changes in occupancy in 10 9 10 km grid squares between two study periods, 1840-1967 and 1968-2015. 3. Statistically significant decreases in occurrence were found for 11 cuckoo wasp species and one host species, while significant increases were not observed for any species. Trends of cuckoo wasps and their hosts were positively correlated, and changes were generally stronger in cuckoo wasps than in their hosts. 4. In a comparative analysis of species traits, abundance, body size and nesting type of host were related to occurrence changes of cuckoo wasps. Scarce and small species that use above ground-nesting hosts declined more than abundant and large species that use ground-nesting hosts. 5. Cuckoo wasp species dependent on dead wood are more vulnerable to changes in the environment than species associated with open sandy habitats. While both groups of species have probably suffered from habitat loss, the emergence of secondary habitats may have benefitted species living in sandy areas and compensated for the negative impact of habitat destruction.
  • Rosa, Elena; van Nouhuys, Saskya; Saastamoinen, Marjo (2017)
    Aggregation can confer advantages in animal foraging, defense, and thermoregulation. There is a tight connection between the evolution of insect sociality and a highly effective immune system, presumably to inhibit rapid disease spread in a crowded environment. This connection is less evident for animals that spend only part of their life cycle in a social environment, such as noneusocial gregarious insects. Our aim was to elucidate the effects of group living by the gregarious larvae of the Glanville fritillary butterfly with respect to individual performance, immunity, and susceptibility to a parasitoid. We were also interested in the role of family relative to common postdiapause environment in shaping life-history traits. Larvae were reared at high or low density and then exposed to the pupal parasitoid wasp Pteromalus apum, either in presence or absence of a previous immune challenge that was used to measure the encapsulation immune response. Surviving adult butterflies were further tested for immunity. The wasp offspring from successfully parasitized butterfly pupae were counted and their brood sex ratios assessed. Larvae reared at high density grew larger and faster than those at low density. Despite high mortality due to parasitism, survival was greater among individuals with high pupal immunity in both density treatments. Moreover, butterfly pupae reared at high density were able to kill a larger fraction of individuals in the parasitoid broods, although this did not increase survival of the host. Finally, a larger proportion of variation observed in most of the traits was explained by butterfly family than by common postdiapause rearing environment, except for adult survival and immunity, for which this pattern was reversed. This gregarious butterfly clearly benefits from high conspecific density in terms of developmental performance and its ability to fight a parasitoid. These positive effects may be driven by cooperative interactions during feeding.