More Like this

1. The Effect of Phenoloxidase Activity on Survival Is Host Plant Dependent in Virus-Infected Caterpillars

   https://doi.org/10.1093/jisesa/ieaa116  

   Resnik, Justine L ; Smilanich, Angela M ( September 2020 , Journal of Insect Science)

   Jaronski, Stefan (Ed.)

   Abstract An important goal of disease ecology is to understand trophic interactions influencing the host–pathogen relationship. This study focused on the effects of diet and immunity on the outcome of viral infection for the polyphagous butterfly, Vanessa cardui Linnaeus (Lepidoptera: Nymphalidae) (painted lady). Specifically, we aimed to understand the role that larval host plants play when fighting a viral pathogen. Larvae were orally inoculated with the entomopathogenic virus, Junonia coenia densovirus (JcDV) (Family Parvoviridae, subfamily Densovirinae, genus Protoambidensovirus, species Lepidopteran protoambidensovirus 1) and reared on two different host plants (Lupinus albifrons Bentham (Fabales: Fabaceae) or Plantago lanceolata Linnaeus (Lamiales: Plantaginaceae)). Following viral infection, the immune response (i.e., phenoloxidase [PO] activity), survival to adulthood, and viral load were measured for individuals on each host plant. We found that the interaction between the immune response and survival of the viral infection was host plant dependent. The likelihood of survival was lowest for infected larvae exhibiting suppressed PO activity and feeding on P. lanceolata, providing some evidence that PO activity may be an important defense against viral infection. However, for individuals reared on L. albifrons, the viral infection had a negligible effect on the immune response, and these individuals also had higher survival and lower viral load when infected with the pathogen compared to the controls. Therefore, we suggest that host plant modifies the effects of JcDV infection and influences caterpillars’ response when infected with the virus. Overall, we conclude that the outcome of viral infection is highly dependent upon diet, and that certain host plants can provide protection from pathogens regardless of immunity. 

   more » « less
2. Use of an exotic host plant shifts immunity, chemical defense, and viral burden in wild populations of a specialist insect herbivore

   https://doi.org/10.1002/ece3.8723  

   Muchoney, Nadya D. ; Bowers, M. Deane ; Carper, Adrian L. ; Mason, Peri A. ; Teglas, Mike B. ; Smilanich, Angela M. ( March 2022 , Ecology and Evolution)

   Defense against natural enemies constitutes an important driver of herbivore host range evolution in the wild. Populations of the Baltimore checkerspot butterfly,Euphydryas phaeton(Nymphalidae), have recently incorporated an exotic plant,Plantago lanceolata(Plantaginaceae), into their dietary range. To understand the tritrophic consequences of utilizing this exotic host plant, we examined immune performance, chemical defense, and interactions with a natural entomopathogen (Junonia coenia densovirus,Parvoviridae) across wild populations of this specialist herbivore. We measured three immune parameters, sequestration of defensive iridoid glycosides (IGs), and viral infection load in field‐collected caterpillars using eitherP.lanceolataor a native plant,Chelone glabra(Plantaginaceae). We found that larvae using the exotic plant exhibited reduced immunocompetence, compositional differences in IG sequestration, and higher in situ viral burdens compared to those using the native plant. On both host plants, high IG sequestration was associated with reduced hemocyte concentration in the larval hemolymph, providing the first evidence of incompatibility between sequestered chemical defenses and the immune response (i.e., the “vulnerable host” hypothesis) from a field‐based study. However, despite this negative relationship between IG sequestration and cellular immunity, caterpillars with greater sequestration harbored lower viral loads. While survival of virus‐infected individuals decreased with increasing viral burden, it ultimately did not differ between the exotic and native plants. These results provide evidence that: (1) phytochemical sequestration may contribute to defense against pathogens even when immunity is compromised and (2) herbivore persistence on exotic plant species may be facilitated by sequestration and its role in defense against natural enemies.

    

   more » « less
3. Microbiome stability and structure is governed by host phylogeny over diet and geography in woodrats ( Neotoma spp.)

   https://doi.org/10.1073/pnas.2108787118  

   Weinstein, Sara B. ; Martínez-Mota, Rodolfo ; Stapleton, Tess E. ; Klure, Dylan M. ; Greenhalgh, Robert ; Orr, Teri J. ; Dale, Colin ; Kohl, Kevin D. ; Dearing, M. Denise ( November 2021 , Proceedings of the National Academy of Sciences)

   The microbiome is critical for host survival and fitness, but gaps remain in our understanding of how this symbiotic community is structured. Despite evidence that related hosts often harbor similar bacterial communities, it is unclear whether this pattern is due to genetic similarities between hosts or to common ecological selection pressures. Here, using herbivorous rodents in the genusNeotoma, we quantify how geography, diet, and host genetics, alongside neutral processes, influence microbiome structure and stability under natural and captive conditions. Using bacterial and plant metabarcoding, we first characterized dietary and microbiome compositions for animals from 25 populations, representing seven species from 19 sites across the southwestern United States. We then brought wild animals into captivity, reducing the influence of environmental variation. In nature, geography, diet, and phylogeny collectively explained ∼50% of observed microbiome variation. Diet and microbiome diversity were correlated, with different toxin-enriched diets selecting for distinct microbial symbionts. Although diet and geography influenced natural microbiome structure, the effects of host phylogeny were stronger for both wild and captive animals. In captivity, gut microbiomes were altered; however, responses were species specific, indicating again that host genetic background is the most significant predictor of microbiome composition and stability. In captivity, diet effects declined and the effects of host genetic similarity increased. By bridging a critical divide between studies in wild and captive animals, this work underscores the extent to which genetics shape microbiome structure and stability in closely related hosts.

    

   more » « less
4. Pollen composition significantly impacts the development and survival of the native small carpenter bee, Ceratina calcarata

   https://doi.org/10.1111/een.12955  

   Lawson, Sarah P. ; Kennedy, Kiley B. ; Rehan, Sandra M. ( October 2020 , Ecological Entomology)

   As native bee populations decrease, there is a need to better understand their nutritional requirements to sustain healthy pollinator populations. A common native bee to eastern North America is the small carpenter bee,Ceratina calcarata. Previous studies have shown that the primary pollen sources forC. calcarataconsist of clover and rose.

   The aim of this study is to compare the effects of diet composition on body size, development and survival. Artificial pollen diets were created using five different ratios of commercially available clover and rose pollen.

   Diets containing higher ratios of clover pollen produced larger individuals with increased survival rates and faster development times. To examine this further, the macronutrient profiles of clover and rose pollen were characterised comparing: protein, sugar, fatty acid, and amino acid content. Results indicated that rose pollen contained significantly higher protein and sugar content, while clover pollen had higher concentrations of essential amino acids. These are crucial to bee health and development, which helps to explain the increased survivorship observed on high clover diet treatments.

   Taken together, these results show that clover pollen provides a higher quality diet for larval development and survival of the native small carpenter bee. This research indicates that diet has a significant effect on the health of the native pollinator community and more research is needed to further explore the balance between pollen quality and availability, including essential macronutrients and the availability of these floral sources for wild bees.

    

   more » « less
5. Additive and interactive effects of anthropogenic stressors on an insect herbivore

   https://doi.org/10.1098/rspb.2022.2431  

   Halsch, Christopher A. ; Zullo, Dominic J. ; Forister, Matthew L. ( April 2023 , Proceedings of the Royal Society B: Biological Sciences)

   The pressures of global change acting on wild plants and animals include exposure to environmental toxins, the introduction of non-native species, and climate change. Relatively few studies have been reported in which these three main classes of stressors have been examined simultaneously, allowing for the possibility of synergistic effects in an experimental context. In this study, we exposed caterpillars of the Melissa blue butterfly ( Lycaeides melissa ) to three concentrations of chlorantraniliprole, under three experimental climates, on a diet of a native or a non-native host plant throughout larval development in a fully factorial experiment. We find that high pesticide exposure and a non-native diet exhibit strong negative effects on caterpillars, resulting in 62% and 42% reduction in survival, respectively, while interactive effects tend to be weaker, ranging from 15% to 22% reduction in survival. Interactive effects have been shown to be strong in other contexts, but do not appear to be universal; however, our study shows that the cumulative effects of stressors acting in isolation (additively) are sufficiently strong to severely reduce survival and by extension population persistence in the wild. 

   more » « less