Biology subjects

Darrington, M.

Publications and source records attributed to Darrington, M..

3 recordsLinked to original sources

bioRxiv2026

Adaptive tracking contributes to the invasion success of a global pest insect

Invasive species are a threat to biodiversity, natural resources, and the economy. Preventing future invasions requires the ability to predict which species will be successful invaders. Invading a new region often requires coping with novel environmental conditions, yet how invading populations adapt to environmental conditions encountered in their introduced range is not always clear. One process that may facilitate invasion in temperate environments is seasonal adaptive tracking, a rapid evolutionary process in which allele frequencies and phenotypes shift in response to seasonal environmental fluctuations, promoting the long-term maintenance of polymorphisms. Here, we test the hypothesis that adaptive tracking is a key contributor to the invasion success of the globally invasive fly Drosophila suzukii. We demonstrate that adaptive tracking results in predictable, rapid evolution of a key thermal tolerance trait (critical thermal minimum) essential for coping with climate variability. We also detect adaptive tracking in several genomic regions enriched for seasonally fluctuating alleles, and these alleles map to loci implicated in diverse traits, including thermal tolerance, pesticide resistance, and olfactory behavior. Finally, we find that loci undergoing adaptive tracking are significantly enriched for alleles associated with invasion in North American populations, suggesting that rapid evolution of seasonal traits may contribute to the success of this invasive species.

evolutionary biology↗

bioRxiv2024

Temperature, but not plant cultivar, influence the efficacy of insecticidal dsRNA in Colorado potato beetle

Environmental RNAi (eRNAi) is a recent innovation in insect pest control, and comprehensive risk assessment is needed to ensure the environmental safety and longevity of this technology. As eRNAi relies on the insects cellular machinery for its mode of action, environmentally mediated plasticity in the activity of cellular processes required for RNAi could influence efficacy and the development of resistance. Here, we investigated the extent to which plant cultivar and temperature influence the efficacy of insecticidal double-stranded RNA (dsRNA) targeting actin in larvae of the Colorado potato beetle (CPB; Leptinotarsa decemlineata). Potato cultivar did not significantly affect survival or gene silencing in dsRNA-treated larvae, indicating that efficacy is consistent across potato varieties, at least under laboratory conditions. However, the amount of leaf tissue consumed by larvae varied across cultivars, with consumption being inversely proportional to protein content. Thus, the ingested dose of dsRNA may vary across crop varieties. Temperature did influence RNAi efficacy, with both gene silencing and mortality being reduced when dsRNA treatment occurred at lower temperatures. After three days of feeding with dsRNA, gene silencing occurred at all temperatures, but knockdown efficiency was 62% at 30{degrees}C and 35% at 18{degrees}C. Beetles consumed significantly less leaf tissue (and thus dsRNA) at 18{degrees}C, but the observed temperature-dependent effects could not be fully explained by the quantity of dsRNA ingested. Further, efficacy at different temperatures was not related to transcript levels of core RNAi genes, indicating that other mechanisms are responsible for the observed effects. Overall, these results indicate that environmental conditions can influence the efficacy of insecticidal eRNAi and may affect the rate at which insects develop resistance to these technologies.

molecular biology↗

bioRxiv2021

Characterisation of the symbionts in the Mediterranean fruitfly gut

Symbioses between bacteria and their insect hosts can range from very loose associations through to obligate interdependence. While fundamental evolutionary insights have been gained from the in-depth study of obligate mutualisms, there is increasing interest in the evolutionary potential of flexible symbiotic associations between hosts and their gut microbiomes. Understanding relationships between microbes and hosts also offers the potential for exploitation for insect control. Here, we investigate the gut microbiome of a global agricultural pest, the Mediterranean fruitfly (Ceratitis capitata). We used 16S rRNA profiling to compare the gut microbiomes of laboratory and wild strains raised on different diets and from flies collected from various natural plant hosts. The results showed that medfly guts harbour a fairly simple microbiome, primarily determined by the larval diet in both wild and laboratory flies. However, regardless of the laboratory diet or natural plant host on which flies were raised, Klebsiella spp dominated the medfly microbiomes and resisted removal by antibiotic treatment. We sequenced the genome of the dominant putative Klebsiella spp (designated Medkleb) isolated from the gut of the Toliman wild type fruitfly strain. Genome-wide ANI analysis placed Medkleb within the K. oxytoca / michiganensis group. Molecular, sequence and phenotypic analyses supported its identity as K. oxytoca. Medkleb has a genome size (5 825 435 bp) which is 1.6 standard deviations smaller than the mean genome size of free-living Klebsiella spp, and lacks some genes involved in environmental sensing. Moreover, the Medkleb genome contains at least two recently acquired unique genomic islands as well as genes that encode pectinolytic enzymes capable of degrading plant cell walls. This may be advantageous given that the medfly diet includes unripe fruits containing high proportions of pectin. These results suggest that the medfly harbours a commensal gut bacterium that may have developed a mutualistic association with its host and provide nutritional benefits.

evolutionary biology↗