The Many Dimensions of Diet Breadth: Phytochemical, Genetic, Behavioral, and Physiological Perspectives on the Interaction between a Native Herbivore and an Exotic Host.

From the perspective of an herbivorous insect, conspecific host plants are not identical, and intraspecific variation in host nutritional quality or defensive capacity might mediate spatially variable outcomes in plant-insect interactions. Here we explore this possibility in the context of an ongoing host breadth expansion of a native butterfly (the Melissa blue, Lycaeides melissa) onto an exotic host plant (alfalfa, Medicago sativa). We examine variation among seven alfalfa populations that differed in terms of colonization by L. melissa; specifically, we examined variation in phytochemistry, foliar protein, and plant population genetic structure, as well as responses of caterpillars and adult butterflies to foliage from the same populations. Regional patterns of alfalfa colonization by L. melissa were well predicted by phytochemical variation, and colonized patches of alfalfa showed a similar level of inter-individual phytochemical diversity. However, phytochemical variation was a poor predictor of larval performance, despite the fact that survival and weight gain differed dramatically among caterpillars reared on plants from different alfalfa populations. Moreover, we observed a mismatch between alfalfa supporting the best larval performance and alfalfa favored by ovipositing females. Thus, the axes of plant variation that mediate interactions with L. melissa depend upon herbivore life history stage, which raises important issues for our understanding of adaptation to novel resources by an organism with a complex life history.

Species with more volatile population dynamics are differentially impacted by weather.

Climatic variation has been invoked as an explanation of population dynamics for a variety of taxa. Much work investigating the link between climatic forcings and population fluctuation uses single-taxon case studies. Here, we conduct comparative analyses of a multi-decadal dataset describing population dynamics of 50 co-occurring butterfly species at 10 sites in Northern California. Specifically, we explore the potential commonality of response to weather among species that encompass a gradient of population dynamics via a hierarchical Bayesian modelling framework. Results of this analysis demonstrate that certain weather conditions impact volatile, or irruptive, species differently as compared with relatively stable species. Notably, precipitation-related variables, including indices of the El Niño Southern Oscillation, have a more pronounced impact on the most volatile species. We hypothesize that these variables influence vegetation resource availability, and thus indirectly influence population dynamics of volatile taxa. As one of the first studies to show a common influence of weather among taxa with similar population dynamics, the results presented here suggest new lines of research in the field of biotic-abiotic interactions.

Socio-ecology of the marsh rice rat (Oryzomys palustris) and the spatio-temporal distribution of Bayou virus in coastal Texas.

Along the southeastern coast of the United States of America (USA), the marsh rice rat (Oryzomys palustris) is the primary host for the hantavirus, genotype Bayou. According to the socio-ecological model for a territorial, polygamous species, females should be distributed across space and time by habitat resources and predation risks, whereas males should space themselves according to the degree of female aggregation and reproductive synchrony. To investigate how females affect the male-male transmission paradigm of Bayou virus, rodents were captured, marked, released in two macrohabitat types and followed across a 30-month period. Microhabitat cover variables were quantified around the individual trap stations. A geodatabase was created from habitat and rodent capture data and analysed in a geographical information system. The ratio of breeding to non-breeding females was ~1:1, with breeding females overly dispersed and non-breeding females randomly dispersed. Spatial analyses revealed both macro- and microhabitat preferences in females. Compared to seronegatives, higher proportions of seropositive adult males were found consistently within closer proximities to breeding females but not to non-breeding females, indicating that male locations were not driven simply by habitat selection. Activities to acquire dispersed receptive females could be an important driver of Bayou virus transmission among male hosts. Herein, we describe an interdisciplinary effort providing a novel approach to elucidate the complexity of hantavirus trafficking and maintenance in rodent populations of a coastal marsh ecosystem.

Benefits and harms of doxycycline treatment for Gulf War veterans' illnesses: a randomized, double-blind, placebo-controlled trial.

BACKGROUND: It has been hypothesized that certain Mycoplasma species may cause Gulf War veterans' illnesses (GWVIs), chronic diseases characterized by pain, fatigue, and cognitive symptoms, and that affected patients may benefit from doxycycline treatment. OBJECTIVE: To determine whether a 12-month course of doxycycline improves functional status in Gulf War veterans with GWVIs. DESIGN: A randomized, double-blind, placebo-controlled clinical trial with 12 months of treatment and 6 additional months of follow-up. SETTING: 26 U.S. Department of Veterans Affairs and 2 U.S. Department of Defense medical centers. PARTICIPANTS: 491 deployed Gulf War veterans with GWVIs and detectable Mycoplasma DNA in the blood. INTERVENTION: Doxycycline, 200 mg, or matching placebo daily for 12 months. MEASUREMENTS: The primary outcome was the proportion of participants who improved more than 7 units on the Physical Component Summary score of the Veterans Short Form-36 General Health Survey 12 months after randomization. Secondary outcomes were measures of pain, fatigue, and cognitive function and change in positivity for Mycoplasma species at 6, 12, and 18 months after randomization. RESULTS: No statistically significant differences were found between the doxycycline and placebo groups for the primary outcome measure (43 of 238 participants [18.1%] vs. 42 of 243 participants [17.3%]; difference, 0.8 percentage point [95% CI, -6.5 to 8.0 percentage points]; P > 0.2) or for secondary outcome measures at 1 year. In addition, possible differences in outcomes at 3 and 6 months were not apparent at 9 or 18 months. Participants in the doxycycline group had a higher incidence of nausea and photosensitivity. LIMITATIONS: Adherence to treatment after 6 months was poor. CONCLUSION: Long-term treatment with doxycycline did not improve outcomes of GWVIs at 1 year.