bioRxiv Science⌕ Search

bioRxiv · 10.1101/2020.03.31.018531

Helminth infection in a suburban ungulate population is driven more by age than landscape variables

Abstract

Wildlife are increasingly common in suburban environments as towns and cities spread into surrounding rural areas. Many wildlife species have adapted to these new environments; however, we know comparatively little about how parasites respond urbanization of host habitats. Parasites are important members within ecological communities and alterations to transmission dynamics are known to alter host population dynamics. For complex life cycle parasites (parasites that use multiple different host species), suburban environments are thought to decrease transmission. Here, infection metrics of two parasites of white-tailed deer, giant liver flukes and thin-necked bladderworms, are examined to determine how successful these parasites are in a suburban environment. Additionally, land cover variables within suburban deer hunting areas are used to test if infection prevalence is associated with certain landscape level metrics. Results indicate that both parasites are common across the suburban landscape and are commonly found coinfecting the same hosts. Prevalence of neither parasite was strongly related to landscape variables within deer hunting areas, but fluke intensity was negatively correlated with the proportion of human development on the landscape. Overall, the scale of transmission events and host-parasite biology may explain why landscape metrics are weak predictors of infection risk in this system.

Explore related subjects

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Vannatta, J. T.. 2020-04-01. Helminth infection in a suburban ungulate population is driven more by age than landscape variables. https://doi.org/10.1101/2020.03.31.018531

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

Phenotypic variation in divergent mitochondrial haplotypes in migratory three-spined stickleback

Mitochondria are essential components in life-sustaining organismal processes. The mitochondrial genome can be influenced by selection, and divergent mitochondrial haplotypes have substantial potential to affect interspecies variation in life-history and physiology, yet little is known about whole organism phenotypic changes that might accompany mitochondrial genomic divergence. Three-spined stickleback on the Scottish island of North Uist provide a model to study this as their populations exhibit a well-mixed nuclear genome, yet two highly diverged mitochondrial haplotypes ( trans-Atlantic and European). Three-spined stickleback were sampled from six lochs to investigate associations between mitochondrial haplotype and phenotypic traits including organ size, body size, and ovule volume/clutch size, as well as citrate synthase enzyme activity. Results showed that mitochondrial haplotype has an influence on male gonadosomatic index (GSI) and potentially citrate synthase (CS) enzyme activity. Differences in male GSI may be explained by the timing of male spermatogenesis or potentially a need for larger testes in European haplotype fish. While no other phenotypic trait showed differences between mitochondrial haplotypes, there were many differences between sexes and populations e.g. in body size and organ/muscle size.

ecology↗

Gregariousness can promote invasion success of pest insects while higher environmental heterogeneity decreases it

Climate change and environmental homogenization are expected to facilitate the expansion of many forest pest insect species and increase the vulnerability of forest ecosystems to insect outbreaks. At present, we lack empirical data on how the antipredator defence traits of pest insects interact with the local environmental conditions and shape outbreak risk. Here we study this and ask 1) how the antipredator defence strategy of pest insects shapes survival under naturally varying predator community, and 2) how is predation risk shaped by the diversity and structure of forests? We tested these questions by conducting a field predation experiment with artificial prey system (prey items made from edible dough) where we manipulated the gregariousness, unpalatability and defensive colouration of prey and tested their effects on prey survival. Additionally, we measured environmental variables and invertebrate predator community structure along the prey transects to analyse how they shape overall predation risk. Our results show that the predation risk was always lowest for gregarious prey irrespective of other defence strategies. Furthermore, our results indicate that predation pressure was lower in more homogenously structured forest areas or areas with a weak quality deadwood continuum in comparison to locations with more natural state forests and good quality deadwood continuum. Altogether, our results suggest that gregariousness can facilitate pest insects to form outbreaks by increasing their survival against generalist predators. However, by maintaining higher heterogeneity in forests, it is possible to ensure higher predation pressure to regulate their population growth.

ecology↗

Two decades of EU pesticide substitution have not reduced impacts on stream invertebrates

Chemical regulation assumes that withdrawing hazardous substances and replacing them with alternatives reduces environmental harm. We tested this premise within the EU pesticide regulatory framework using a 23-year record of event-driven pesticide exposure and stream-invertebrate communities from 152 German agricultural streams sampled between 1998 and 2021. Neither pesticide toxic pressure nor pesticide-related invertebrate impairment showed a detectable decline over time, and an improvement equivalent to one ecological status class can be excluded. Dominant toxicity drivers shifted from organophosphates to neonicotinoids and subsequently to pyrethroids, yet the relationship between toxic pressure and community effects remained consistent despite their distinct modes of action. Sustained toxic pressure reflected three mechanisms: successive chemical substitution, prolonged approval periods, and continued exposure to substances no longer authorised as plant protection products. Substitution thus changed which chemicals harm streams, not how much. Measured field outcomes must become the benchmark of pesticide regulation.

ecology↗