Biology subjects

Denver, D.

Publications and source records attributed to Denver, D..

3 recordsLinked to original sources

bioRxiv2026

Population Genetic Structure of Ariolimax columbianus around Corvallis, Oregon, USA

Urbanization has been previously shown to affect evolution of plants and animals by restricting gene flow, increasing genetic drift, and causing divergent selection between rural and urban populations, however, the effect of urbanization on terrestrial gastropod evolution has only been minimally researched. Most research on terrestrial gastropods primarily focusing on invasive pest species, and little attention is given to native species like Ariolimax columbianus (Pacific banana slug). There is no current published research on the phylogeography of A. columbianus. In this study, surface epithelial cells from 66 Ariolimax columbianus individuals were collected from 11 locations around Corvallis, Oregon, and one site in northern California. These samples were amplified and sequenced at two loci: cytochrome oxidase 1 (CO1) and the internal transcribed spacer 2 (ITS-2). This data was used to generate maximum-likelihood phylogenetic trees to better understand the population genetics of these local native gastropods. The CO1 phylogenetic analysis showed two major haplotypes around the city of Corvallis - northwestern and southern, while the ITS-2 phylogenetic analysis showed three general haplotypes around the city - northern, western, and southern. The results in this study show the presence of genetic breaks between many of these populations, possibly due to a combination of factors including anthropogenic fragmentation, natural barriers, and the low active dispersal ability of A. columbianus. However, the extent that each of those factors has on disrupting gene flow and explaining patterns of genetic variation in this species requires further research. The present study acts as a foundation for the development of future research on banana slug phylogenetics and population genetic structure.

genetics↗

bioRxiv2026

Two Pellioditis biocontrol nematode species infect Ariolimax columbianus, the Pacific banana slug, and increase mortality in laboratory infectivity trials

Gastropods are a highly diverse and often overlooked taxonomic group of significant ecological and economic importance. Some terrestrial gastropods are critical pests of commercial agriculture and home gardens worldwide. Malacopathogenic nematodes offer an effective biological control method of managing pest slugs and snails as a natural enemy. Pellioditis (syn. Phasmarhabditis) hermaphrodita and Pellioditis (syn. Phasmarhabditis) californica are two species of biocontrol nematodes that have been commercialized, sold as Nemaslug(R) and Nemaslug(R) 2.0 respectively on three continents. Although there is interest in bringing Nemaslug(R) products to the US, they are currently not permitted due to limited knowledge on their North American distribution and effects on non-target and native species. In this study, we investigated the impact of P. hermaphrodita and P. californica on Ariolimax columbianus across two slug-host life stages, in laboratory infectivity assays. The objectives were to 1. determine whether P. hermaphrodita and P. californica nematodes impact survival of A. columbianus, and 2. evaluate whether there are differential effects on survival in juvenile and adult life stages of A. columbianus, in laboratory infectivity trials. We found that P. hermaphrodita caused significant mortality in A. columbianus with 100% mortality observed in both juvenile and adult slug hosts. The P. californica treatment had significant effects on the juvenile A. columbianus group only, with 80% mortality. By contrast, only 16% of unexposed control juveniles and 4% of control adult slugs died during the experiment. These results indicate that P. hermaphrodita and P. californica are lethal to the native, non-target Pacific banana slug (A. columbianus) under laboratory conditions, with mortality differing between juvenile and adult host life stages. Given the ecological importance of A. columbianus, these findings raise concerns for potential non-target effects of P. californica and P. hermaphrodita on terrestrial gastropod communities and emphasize the need for testing biocontrol agents against multiple life stages.

zoology↗

bioRxiv2025

Microbiome dynamics associated with the infection of grey field slugs by the biocontrol nematode Phasmarhabditis hermaphrodita

The facultative-parasitic nematode Phasmarhabditis hermaphrodita has been used for many years as a biological control agent targeting slug pests. During the nematodes infection process, the presence of certain bacteria has been suggested to affect the pathogenicity and efficiency of the nematodes in killing slugs, though the potential roles of different bacteria in affecting host-infection by nematodes remains unclear. In this study, we examined three experimental P. hermaphrodita populations cultured with three different bacteria: 1) Escherichia coli (EC), 2) a newly isolated Pseudomonas sp. Strain (PS) that co-cultured with a P. hermaphrodita strain found in Oregon, USA, and 3) the original complex bacterial community (BC) associated with the nematode. For each of the three treatments, we evaluated the pathogenicity of P. hermaphrodita at a low and high concentration towards adult Deroceras reticulatum (Mollusca: Gastropoda) and investigated the changes in the nematode microbiome structure before and after slug infection. Slugs exposed to EC low treatments (LT50: 8.61 days) and EC high treatments (LT50: 7.74 days) survived significantly longer than slugs exposed to PS high (LT 50: 5.68 days) and BC high (LT50: 5.92 days). Slugs in the BC low treatment (LT50: 6.77 days) survived significantly longer when compared to BC high, but survival was significantly shorter when compared to EC high. We identified a wide variety of taxa components (82 genera) in the community associated with the nematode pre-infection, most of which are of low abundance. In all bacterial treatments post-infection, the number of genera almost quadrupled and those taxas abundance changed remarkably, although the taxa with the highest abundance remained stable. We also observed four Pseudomonas amplicon sequence variants (ASVs) that increased in abundance after slug infection in the Pseudomonas treatment, which may suggest a role of the taxa in the infection process.

microbiology↗