Asymmetry in host and parasitoid diffuse coevolution: when the red queen has to keep a finger in more than one pie

BACKGROUND: Coevolution between pairs of antagonistic species is generally considered an endless "arms race" between attack and defense traits to counteract the adaptive responses of the other species. PRESENTATION OF THE HYPOTHESIS: When more than two species are involved, diffuse coevolution of hosts and parasitoids could be asymmetric because consumers can choose their prey whereas preys do not choose their predator. This asymmetry may lead to differences in the rate of evolution of the antagonistic species in response to selection. The more long-standing the coevolution of a given pair of antagonistic populations, the higher should be the fitness advantage for the consumer. Therefore, the main prediction of the hypothesis is that the consumer trophic level is more likely to win the coevolution race. TESTING THE HYPOTHESIS: We propose testing the asymmetry hypothesis by focusing on the tritrophic system plant/aphid/aphid parasitoid. The analysis of the genetic variability in the virulence of several parasitoid populations and in the defenses of several aphid species or several clones of the same aphid species could be compared. Moreover, the analysis of the neutral population genetic structure of the parasitoid as a function of the aphid host, the plant host and geographic isolation may complement the detection of differences between host and parasitoid trophic specialization. IMPLICATIONS OF THE HYPOTHESIS: Genetic structures induced by the arms race between antagonistic species may be disturbed by asymmetry in coevolution, producing neither rare genotype advantages nor coevolutionary hotspots. Thus this hypothesis profoundly changes our understanding of coevolution and may have important implications in terms of pest management

Coordinated \u3ci\u3eDiabrotica\u3c/i\u3e Genetics Research: Accelerating Progress on an Urgent Insect Pest Problem

Diabrotica spp. (western, northern, and Mexican corn rootworms) represent the main pest complex of continuous field corn, Zea mays (L.), in North America. The western corn rootworm, Diabrotica virgifera virgifera LeConte, also has become the main pest of continuous corn in Central and Southeastern Europe since its introduction near Belgrade 15–20 years ago, and it represents a major risk to Western Europe. It has already caused economic losses in Eastern Europe, and Western countries such as France have committed large expenditures for containment and/or eradication. Rootworm larvae feed on corn roots, and damaged plants are more susceptible to drought and disease, have decreased yield, and are prone to lodging. A recent economic analysis estimates that costs of control and yield loss are about $1.17 billion a year in the United States. Crop rotation and chemical control have been the primary management strategies, but the western corn rootworm is becoming increasingly difficult to control because of its sequential ability to evolve resistance to almost all management strategies that have been used. The recent deployment of transgenic Bt corn in the United States for controlling Diabrotica pests has raised concerns that rootworms will develop resistance to this technology as well, unless appropriate resistance management strategies are developed and practiced

Coordinated \u3ci\u3eDiabrotica\u3c/i\u3e Genetics Research: Accelerating Progress on an Urgent Insect Pest Problem

Diabrotica spp. (western, northern, and Mexican corn rootworms) represent the main pest complex of continuous field corn, Zea mays (L.), in North America. The western corn rootworm, Diabrotica virgifera virgifera LeConte, also has become the main pest of continuous corn in Central and Southeastern Europe since its introduction near Belgrade 15–20 years ago, and it represents a major risk to Western Europe. It has already caused economic losses in Eastern Europe, and Western countries such as France have committed large expenditures for containment and/or eradication. Rootworm larvae feed on corn roots, and damaged plants are more susceptible to drought and disease, have decreased yield, and are prone to lodging. A recent economic analysis estimates that costs of control and yield loss are about $1.17 billion a year in the United States. Crop rotation and chemical control have been the primary management strategies, but the western corn rootworm is becoming increasingly difficult to control because of its sequential ability to evolve resistance to almost all management strategies that have been used. The recent deployment of transgenic Bt corn in the United States for controlling Diabrotica pests has raised concerns that rootworms will develop resistance to this technology as well, unless appropriate resistance management strategies are developed and practiced

Coordinated \u3ci\u3eDiabrotica\u3c/i\u3e Genetics Research: Accelerating Progress on an Urgent Insect Pest Problem

Diabrotica spp. (western, northern, and Mexican corn rootworms) represent the main pest complex of continuous field corn, Zea mays (L.), in North America. The western corn rootworm, Diabrotica virgifera virgifera LeConte, also has become the main pest of continuous corn in Central and Southeastern Europe since its introduction near Belgrade 15–20 years ago, and it represents a major risk to Western Europe. It has already caused economic losses in Eastern Europe, and Western countries such as France have committed large expenditures for containment and/or eradication. Rootworm larvae feed on corn roots, and damaged plants are more susceptible to drought and disease, have decreased yield, and are prone to lodging. A recent economic analysis estimates that costs of control and yield loss are about $1.17 billion a year in the United States. Crop rotation and chemical control have been the primary management strategies, but the western corn rootworm is becoming increasingly difficult to control because of its sequential ability to evolve resistance to almost all management strategies that have been used. The recent deployment of transgenic Bt corn in the United States for controlling Diabrotica pests has raised concerns that rootworms will develop resistance to this technology as well, unless appropriate resistance management strategies are developed and practiced

Differences between independently invading and crossed populations of the alien maize pest Diabrotica virgifera virgifera

Unterschiede zwischen unabhängig einwandernden und gekreuzten Populationen des neuen Maisschädlings Diabrotica virgifera virgifer

Peer Community In: a free process for the recommendation of preprints based on peer review

Peer Community In: a free process for the recommendation of preprints based on peer review. FORCE201

Role of a gamma-aminobutryic acid (GABA) receptor mutation in the evolution and spread of Diabrotica virgifera virgifera resistance to cyclodiene insecticides

The western corn rootworm, Diabrotica virgifera virgifera, is a damaging pest of cultivated corn that was controlled by applications of cyclodiene insecticides from the late 1940s until resistance evolved ∼10 years later. Range expansion from the western plains into eastern USA coincides with resistance development. An alanine to serine amino acid substitution within the Rdl subunit of the gamma-aminobutyric acid (GABA) receptor confers resistance to cyclodiene insecticides in many species. We found that the non-synonymous single nucleotide polymorphism (SNP) G/T at the GABA receptor cDNA position 838 (G/T838) of D. v. virgifera resulted in the alanine to serine change, and the codominant SNP allele T838 was genetically linked to survival of beetles in aldrin bioassays. A phenotypic gradient of decreasing susceptibility from west to east was correlated with higher frequencies of the resistance-conferring T838 allele in the eastern-most populations. This pattern exists in opposition to perceived selective pressures since the more eastern and most resistant populations probably experienced reduced exposure. The reasons for the observed distribution are uncertain, but historical records of the range expansion combined with the distribution of susceptible and resistant phenotypes and genotypes provide an opportunity to better understand factors affecting the species\u27 range expansion

Western corn rootworm (Diabrotica virgifera virgifera LeConte) population dynamics

The western corn rootworm Diabrotica virgifera virgifera LeConte is a major insect pest of field maize, Zea mays L. Larvae can cause substantial injury by feeding on maize roots. Larval feeding may destroy individual roots or root nodes, and reduce plant growth, stability, and yield. Costs associated with managing corn rootworms in continuous maize are annually one of the largest expenditures for insect management in the United States Corn Belt. Even though D. virgifera virgifera has been studied intensively for over 50 years, there is renewed interest in the biology, ecology, and genetics of this species because of its ability to rapidly adapt to management tactics, and its aggressive invasive nature. This article provides a comprehensive review of D. virgifera virgifera population dynamics, specifically: diapause, larval and adult development, seasonality, spatial and temporal dynamics at local and landscape scales, invasiveness in North America and Europe, and non-trophic interactions with other arthropods. Gaps in current knowledge are identified and discussed especially within the context of challenges that scientists in North America and Europe are currently facing regarding pest dynamics and the need to develop appropriate management strategies for each geographic area

Genome scan of \u3ci\u3eDiabrotica virgifera virgifera\u3c/i\u3e for genetic variation associated with crop rotation tolerance

Crop rotation has been a valuable technique for control of Diabrotica virgifera virgifera for almost a century. However, during the last two decades, crop rotation has ceased to be effective in an expanding area of the US corn belt. This failure appears to be due to a change in the insect’s oviposition behaviour, which, in all probability, has an underlying genetic basis. A preliminary genome scan using 253 amplified fragment-length polymorphism (AFLP) markers sought to identify genetic variation associated with the circumvention of crop rotation. Samples of D. v. virgifera from east-central Illinois, where crop rotation is ineffective, were compared with samples from Iowa at locations that the behavioural variant has yet to reach. A single AFLP marker showed signs of having been influenced by selection for the circumvention of crop rotation. However, this marker was not diagnostic. The lack of markers strongly associated with the trait may be due to an insufficient density of marker coverage throughout the genome. A weak but significant general heterogeneity was observed between the Illinois and Iowa samples at microsatellite loci and AFLP markers. This has not been detected in previous population genetic studies of D. v. virgifera and may indicate a reduction in gene flow between variant and wild-type beetles