Rates Of Successful Parasitism Research Articles

The effect of Common Cuckoo parasitism on the annual productivity of a host population

Avian interspecific brood parasitism is an excellent system for studying coevolutionary processes in nature because brood parasites directly affect host reproductive success. Most research on avian brood parasitism has, therefore, focused primarily on specific host anti-parasite behaviours and parasite counter-adaptations. However, the population-level consequences of brood parasitism for host species are poorly understood. This study investigated the effect of Common Cuckoo (Cuculus canorus) parasitism on the productivity of a local population of the Great Reed Warbler (Acrocephalus arundinaceus) host in south-western Slovakia. A total of 495 females nesting at the studied site successfully fledged 1321 of their own young and 63 young of the Common Cuckoo over the course of 15 years (2008–2022), and the annual rate of successful parasitism ranged from 18% to 44% over this period. As predicted, higher rates of successful cuckoo parasitism significantly reduced the annual productivity of the local Great Reed Warbler population, and its contribution to decreased host reproductive success was at about the same rate as overall nest failure caused by predation and other environmental factors. Such a heavily parasitized population was probably maintained by immigrants from other populations and density-dependent selection, which is also consistent with source–sink dynamics. However, further long-term studies monitoring parasitized populations are required to confirm these findings.

Host preference of three Asian larval parasitoids to closely related Drosophila species: implications for biological control of Drosophila suzukii

Insect parasitoids can attack phylogenetically related hosts that share similar physiological properties and defense mechanisms and, more importantly, overlapping ecological niches. Here, host preferences of three parasitoids, Asobara japonica (Hymenoptera: Braconidae), Ganaspis brasiliensis and Leptopilina japonica (Hymenoptera: Figitidae), were examined on two closely related hosts, Drosophila suzukii and D. melanogaster (Diptera: Drosophilidae). Each parasitoid’s rate of successful parasitism (or offspring survival) on these hosts was first compared in no choice tests. Results showed that A. japonica had higher parasitism levels than G. brasiliensis and L. japonica, and that offspring survival for all parasitoids was similar on both host species. Host preferences in choice tests were then compared, with each parasitoid presented with the two host species at different proportions of host abundance. None of the parasitoids showed host preference or host switching, even though these parasitoids have different degrees of host specificity, from more generalized (A. japonica) to more specialized (G. brasiliensis). Further examination of parasitoid olfactory responses showed all three parasitoid species were attracted to volatiles from fruit infested by either host species and showed no preference to either D. suzukii or D. melanogaster. Results suggest that the hosts’ phylogenetical similarity and a lack of any obvious fitness costs for offspring survival may reduce host preference by these larval parasitoids.

Density-Dependent Growth and Fitness in Dastarcus helophoroides (Coleoptera: Bothrideridae).

The ectoparasitoid Dastarcus helophoroides Fairmaire (Coleoptera: Bothrideridae) is an important natural enemy insect, which is artificially mass-reared and released into woodland to control medium and large longhorn beetle species. This study examined the developmental duration (days) of larvae and adult fitness (including numbers of adults emerging per host and mean body size) by exposing a single substitute host, a pupa of Zophobas morio (Coleoptera: Tenebrionidae), to different densities of D. helophoroides larvae. We showed that there was no significant effect on the rate of successful parasitism and cocoon formation, but emergence success and measures of individual adult body size (length, width, and weight) declined with increasing larval density. Larval period and cocoon period increased with larval density, while total weight of adults emerging per host increased initially before reaching a plateau. Our results suggest that a pupa of Z. morio could be successfully parasitized by a single D. helophoroides larva, but multiple D. helophoroides larvae can share one host. Excessive larval density caused intraspecific competition among D. helophoroides larvae, manifesting in extended developmental duration of immature stage and reduced fitness of adults. Furthermore, the tradeoff between the numbers of adults and body size may stabilize the population dynamics with detectable mutual interference, particularly in competing for limited host resources. These findings suggest six larvae per host would achieve the highest adult fitness and would enhance mass-rearing techniques as part of IPM strategies for longhorn beetles.

Why do hosts with obvious egg polymorphism suffer low parasitism rates under avian brood parasitism? A theoretical consideration

Polymorphism is a general phenomenon in the natural world evolving as a result of frequency-dependent selection. Such polymorphism has recently received increasing attention in parasitic cuckoo-host systems, in which egg polymorphism in hosts is regarded as a specific adaptation against cuckoo parasitism. Here, we provided a theoretical analysis to investigate the effect of host egg polymorphism on the rate of successful parasitism (SPR) by cuckoos to help better understand the role of egg polymorphism in cuckoo-host systems. Five key conclusions can be drawn from these calculations: (1) The contrast of egg phenotypes in hosts significantly reduces cuckoo fitness by reducing the SPR of cuckoos; (2) hosts can minimize the SPR of cuckoos by laying polymorphic eggs with equal proportion of the two morphs if cuckoos also evolve egg dimorphism as a counter-adaptation; (3) the escalation of egg polymorphism in hosts further reduces the SPR in cuckoos, although the efficiency of such an effect decreases with the number of host egg morphs; (4) cuckoos can maximize their SPR by laying a ratio of egg morphs equal to the ratio of host egg morphs; and (5) an increase in the number of cuckoo egg morph does not increase the total SPR of cuckoos for parasitizing hosts with polymorphic eggs. Egg polymorphism in hosts is regarded as a specific adaptation against cuckoo parasitism. Here, we provided a theoretical analysis to show that the disruptive evolution of egg phenotypes in hosts significantly reduces cuckoo fitness by reducing the rate of successful parasitism by cuckoos (SPR). Hosts with obvious egg polymorphism suffer low parasitism rates and they can minimize the SPR of cuckoos by laying polymorphic eggs with equal proportions of the two morphs if cuckoos also evolve egg dimorphism as a counteradaptation, whilst cuckoos can maximize their SPR by laying a ratio of egg morphs equal to the ratio of host egg morphs. Egg polymorphism in hosts is regarded as a specific adaptation against cuckoo parasitism. Here, we provided a theoretical analysis to show that the disruptive evolution of egg phenotypes in hosts significantly reduces cuckoo fitness by reducing the rate of successful parasitism (SPR) by cuckoos. Hosts with obvious egg polymorphism suffer low parasitism rates and they can minimize the SPR of cuckoos by laying polymorphic eggs with equal proportions of the two morphs if cuckoos also evolve egg dimorphism as a counteradaptation, whilst cuckoos can maximize their SPR by laying a ratio of egg morphs equal to the ratio of host egg morphs.

WASP-ASSOCIATED FACTORS ACT IN INTERSPECIES COMPETITION DURING MULTIPARASITISM.

Coexistence or displacement of parasitoids in hosts during intrinsic competitive interactions between different parasitoid species (multiparasitism) may depend on their life history traits and behavior. Intense competition for possession of hosts may lead to the elimination of the inferior competitor through physical attack and/or physiological suppression. However, the mechanisms of physiological suppression during multiparasitism remain unclear. Previous work has shown that first instar larvae of the solitary endoparasitoid Meteorus pulchricornis possess well-developed mandibles that are used to kill competitors. Two gregarious endoparasitoids, Cotesia kariyai and C. rufricus, share host resources especially when the time gap of oviposition is short. Here, we investigated the physiological influence of wasp-regulatory factors of the three endoparasitoids, M. pulchricornis, C. kariyai, and C. ruficrus, in their common host Mythimna separata. We found that MpVLP alone (or with venom) deleteriously affected the development of the two gregarious species. Similarly, CkPDV plus venom had toxic effect on M. pulchricornis eggs and immature larvae, although they were not harmful to immature stages of C. ruficrus. Cotesia kariyai and C. ruficrus were able to coexist mainly through the expression of regulatory factors and both could successfully emerge from a multiparasitized host. The injection of CkPDV plus venom after oviposition in L5 host larvae facilitated C. ruficrus development and increased the rate of successful parasitism from 9% to 62%. This suggests that the two gregarious parasitoid wasps exhibit strong phylogenetic affinity, favoring their coexistence and success in multiparasitized hosts.

Effect of Mutual Interference on the Ability of Spalangia cameroni (Hymenoptera: Pteromalidae) to Attack and Parasitize Pupae of Stomoxys calcitrans (Diptera: Muscidae).

We investigated the effect of mutual interference on the attack efficiency and the rate of successful parasitism on the parasitoid Spalangia cameroni (Perkins) attacking pupae of the stable fly Stomoxys calcitrans (L.). Female parasitoids (2, 4, 8, 16, or 32) were exposed to 100 fly pupae during 24 h. The number of pupae that were attacked and the number successfully parasitized increased with the parasitoid density and reached a maximum of ∼70 and 50, respectively. Parasitoid-induced mortality (PIM) was about 20 pupae, irrespective of parasitoid density. The per capita rates of attack, successful parasitism and parasitoid-induced mortality declined monotonously with parasitoid density. Progeny sex ratio was female biased for all parasitoid densities, but declined significantly with increasing parasitoid density from ∼70% females at the lowest density to ∼60% at the highest. Mutual interference was incorporated into a functional response model to predict the attack rate and the rate of successful parasitism at different temperatures, host densities and parasitoid densities. The model explained 93.5% of the variation in the observed number of attacked pupae and 91.5% of the variation in the number of successfully parasitized pupae. The model predicts that increasing parasitoid densities will increase the percentage of killed hosts, but only up to a certain density. Above this density, a further increase in parasitoid abundance will actually lead to a decline in the percentage parasitism. These findings may have some implications for using S. cameroni in biological control against flies using inundative releases.

Temperature-Dependent Functional Response of Spalangia cameroni (Hymenoptera: Pteromalidae), a Parasitoid of Stomoxys calcitrans (Diptera: Muscidae).

The effects of host density, temperature, and burial depths on the functional response of the synovigenic parasitoid Spalangia cameroni (Perkins) attacking pupae of the stable fly Stomoxys calcitrans (L.) were examined. Five temperatures (15, 20, 25, 30, and 35°C), six host densities (2, 4, 8, 16, 32, and 64 pupae per 19.64 cm(2)), and three burial depths in whole wheat grains (0, 8, and 16 cm) were used. It was demonstrated that temperature had a profound effect on the functional response, whereas burial depths of the pupae played a minor role. For all temperatures, the functional response was of type 2 with an upper asymptote that depends on the temperature. Data were fitted by a functional response model where only the maximum attack rate is temperature dependent. The model shows that the optimal temperature for S. cameroni for attacking S. calcitrans pupae is 28.6°C, where the maximum attack rate is 20.2 pupae day(-1). The lower and upper temperature thresholds for attacks were found as 8.1 and 36.6°C, respectively. The temperature range for attacks that resulted in successful parasitism was narrower, namely, 15.0 and 35.5°C. Maximum rate of successful parasitism was estimated to be 18.2 progeny day(-1) occurring at 27.9°C. The proportion of attacks resulting in successful parasitism increased steeply with temperatures >15°C and declined steeply at temperatures >30°C.

Strong specificity in the interaction between parasitoids and symbiont‐protected hosts

Coevolution between hosts and parasites may promote the maintenance of genetic variation in both antagonists by negative frequency-dependence if the host-parasite interaction is genotype-specific. Here we tested for specificity in the interaction between parasitoids (Lysiphlebus fabarum) and aphid hosts (Aphis fabae) that are protected by a heritable defensive endosymbiont, the γ-proteobacterium Hamiltonella defensa. Previous studies reported a lack of genotype specificity between unprotected aphids and parasitoids, but suggested that symbiont-conferred resistance might exhibit a higher degree of specificity. Indeed, in addition to ample variation in host resistance as well as parasitoid infectivity, we found a strong aphid clone-by-parasitoid line interaction on the rates of successful parasitism. This genotype specificity appears to be mediated by H.defensa, highlighting the important role that endosymbionts can play in host-parasite coevolution.

Indirect interactions between an introduced and a native ladybird beetle species mediated by a shared parasitoid

Abstract We studied parasitism rates by Dinocampus coccinellae (Schrank) of the native species Coleomegilla maculata De Geer and the introduced Harmonia axyridis (Pallas) in the laboratory and in the field. The rate of successful parasitism for H. axyridis was lower than for C. maculata , but the proportion of the population that had immature stages of the parasitoid was similar for both species. We used a population dynamics model to predict interactions between C. maculata , H. axyridis , and D. coccinellae , incorporating the differences in suitability we found between the two hosts. In the model, parasitoid attacks on non-suitable hosts contribute to parasitoid egg depletion without causing host death or parasitoid recruitment. Thus, hosts with low suitability could act as sinks for parasitoid eggs. Simulations of this model suggest that there is a critical value of the growth rate ( r ) for C. maculata below which C. maculata goes extinct. The critical r value is an increasing function of the attack rate on C. maculata (as expected) and a decreasing function of the attack rate on H. axyridis because the strength of H. axyridis as an egg sink increases with the attack rate on this species. Simulations of the model using experimentally derived parameter values suggest that the presence of H. axyridis leads to an increase in equilibrium densities of C. maculata . This outcome is due to the wastage of parasitoid eggs in the relatively unsuitable H. axyridis hosts.

Aphid population dynamics: does resistance to parasitism influence population size?

Summary1. Insect population size is regulated by both intrinsic traits of organisms and extrinsic factors. The impacts of natural enemies are typically considered to be extrinsic factors, however insects have traits that affect their vulnerability to attack by natural enemies, and thus intrinsic and extrinsic factors can interact in their effects on population size.2. Pea aphids Acyrthosiphon pisum Harris (Hemiptera: Aphididae) in New York and Maryland that are specialised on alfalfa are approximately two times more physiologically resistant to parasitism by Aphidius ervi Haliday (Hymenoptera: Braconidae) than pea aphids specialised on clover. To assess the potential influence of this genetically based difference in resistance to parasitism on pea aphid population dynamics, pea aphids, A. ervi, and other natural enemies of aphids in clover and alfalfa fields were sampled.3. Rates of successful parasitism by A. ervi were higher and pea aphid population sizes were lower in clover, where the aphids are less resistant to parasitism. In contrast, mortality due to a fungal pathogen of pea aphids was higher in alfalfa. Generalist aphid predators did not differ significantly in density between the crops.4. To explore whether intrinsic resistance to parasitism influences field dynamics, the relationship between resistance and successful field parasitism in 12 populations was analysed. The average level of resistance of a population strongly predicts rates of successful parasitism in the field. The ability of the parasitoid to regulate the aphid may vary among pea aphid populations of different levels of resistance.

PEA APHID–PARASITOID INTERACTIONS: HAVE PARASITOIDSADAPTED TO DIFFERENTIAL RESISTANCE?

In insect host–parasitoid systems, successful immune responses of the host kill the parasitoid, and successful development of the parasitoid will kill the host. Thus, hosts and their parasitoids can exert strong selection on each other that may lead to the coevolution of host defense traits and parasitoid counter-defenses. In upstate New York, pea aphids (Acyrthosiphon pisum) specialized on alfalfa are, on average, two times more physiologically resistant to parasitism by Aphidius ervi parasitoids than pea aphids specialized on clover. There is genetic variation within populations of Aphidius ervi in the ability to overcome pea aphid resistance; thus an evolutionary response to the differences in aphid resistance is possible. Here, I document that pea aphid populations that are more resistant to parasitism in laboratory assays exhibit lower rates of parasitism in the field, suggesting that the genetically based differences in aphid resistance may influence rates of successful parasitism. I found that the difference in resistance between pea aphids specialized on alfalfa or on clover in New York is present in additional populations of pea aphids assayed over several years and is present in Maryland as well as New York. However, despite the potentially large difference in selective regimes due to differences in aphid resistance, parasitoids collected from alfalfa fields and clover fields do not differ in their ability to overcome pea aphid resistance. There is no evidence that they are adapted to aphids from their home crop, or locally adapted to aphids from their home field. The mobility of this parasitoid, and its relatively recent introduction to North America as a biological control agent, may contribute to the lack of adaptation.

Dispersal of Muscidifurax raptorellus Kogan and Legner (Hymenoptera: Pteromalidae) in a High-Rise Poultry Facility

Abstract House flies, Musca domestica L., breed rapidly in poultry house manure and consequently pose a nuisance and public health threat. We studied the dispersal of commercially produced Muscidifurax raptorellus Kogan and Legner, a biological control agent of flies, in a high-rise poultry facility in Pennsylvania. We released this pupal parasitoid at three densities in the pit of a poultry house and recorded emergence of F 1 and F 2 progeny from spatially referenced field-collected and laboratory-reared sentinel hosts over a 10-week period. Among the F 1 progeny, there were higher rates of successful parasitism from laboratory-reared hosts, rendering them more suitable indicators of dispersal than field-collected conspecifics for the first generation. Overall, the emergence of both F 1 and F 2 progeny of M. raptorellus decreased exponentially over distance, with the greatest emergence occurring within 2 m of release points, suggesting its utility as a site-specific control tactic of house flies.

Genetic and epigenetic variation in suitability of a Drosophila host to three parasitoid species

The genetic and epigenetic variability in suitability of a host, Drosophila melanogaster Meigen, for the development of three parasitoid species (Leptopilina boulardi (Barbotin, Carton, and Kelmer-Pillault), Leptopilina heterotoma (Thompson), and Pachycrepoideus dubius Ashmead) was analyzed. The Drosophila population came from an oasis in central Tunisia, where it is infested by the three wasp species. The genetic variability of the host was analyzed by the technique of using isofemale lines. The host population exhibited no genetic variability in the degree of infestation except in the case of L. heterotoma. It did, however, show a high level of genetic variability concerning its suitability for development of the three parasitoids. The experimental conditions had a significant effect on infestation by two of the parasitoids (L. boulardi, L. heterotoma). The rates of successful parasitism were correlated only in the case of the two eucoilid parasitoids. Therefore, a single host genotype was not suitable for all three parasitoid species concomitantly. Under pressure from the three parasitoids, the host population maintained genetic variability of its response to parasitoid development.

Evolutionary relationships to parasitism by seven species of the Drosophila melanogaster subgroup

Parasitic wasps are an important component of the niche of Drosophila species. The susceptibility to the Cynipid Leptopilina boulardi was estimated in the seven sibling species of Drosophila belonging to the melanogaster subgroup. Three categories of Hies can be distinguished, according to the level of cellular immune reaction and success of parasitism. Drosophila melanogaster and D. mauritiana belong to the category 1, specified by no encapsulative reaction and a high rate of successful parasitism. Category 2, characterized by a moderate encapsulation rate and a high mortality include D. simulans.5, D. erecta and D. orena. Category 3, with D. yakuba and D. tcissien, is specified by a very low rate or absence of successful parasitism due to a highly efficient immune cellular reaction. This classification parallels the phylogenic relationship based upon polytene chromosome banding sequences. Such specific ditferences in susceptibility to parasites may plan an important role in the competition between these species in Africa.