Biased parasitoid sex ratios: Wolbachia, functional traits, local and landscape effects

Effect of Ultraviolet-B Radiating Drosophila melanogaster as Host on the Quality of Trichopria drosophilae, a Pupal Parasitoid of Drosophila suzukii

The pupal parasitoid, Trichopria drosophilae Perkins (Hymenoptera: Diapriidae), is an ectoparasitoid of the genus Drosophila with great potential for application in biological control based on its excellent control efficiency for Drosophila suzukii Matsumura (Diptera: Drosophilidae), and it has has even been commercialized by biofactories. Due to its characteristics of short life cycle, large number of offspring, easy rearing, rapid reproduction, and low cost, Drosophila melanogaster (Diptera: Drosophilidae) is currently being utilized as a host to mass produce T. drosophilae. To simplify the mass rearing process and omit the separation of hosts and parasitoids, ultraviolet-B (UVB) was used as an irradiation source to irradiate D. melanogaster pupae, and the effects on T. drosophilae were studied. The results showed that UVB radiation significantly reduces host emergence and affects the duration of parasitoid development (female: F0 increased from 21.50 to 25.80, F1 from 23.10 to 26.10; male: F0 decreased from 17.00 to 14.10, F1 from 17.20 to 14.70), which has great significance for the separation of hosts and parasitoids as well as of females and males. Of the various studied conditions, UVB irradiation was ideal when the host was supplied with parasitoids for 6 h. The selection test results showed that the female-to-male ratio of emerging parasitoids in this treatment was highest at 3.47. The no-selection test resulted in the highest rates of parasitization and parasitoid emergence rate, maximized inhibition of host development, and allowed the omission of the separation step. Finally, the results of the semi-field test showed that the parasitoids bred in this treatment could search for their hosts normally and could therefore be directly applied in the biological control of Drosophila pests in the field.

Spatiotemporal variation in the adult sex ratio, male aggregation, and movement of two tropical cloud forest dung beetles

While theory suggests that at conception the sex ratio should be balanced (1:1), this can be variable across space and time in wild populations. Currently, studies of the environmental factors that regulate adult sex ratio (ASR) in species with different life history traits are scarce. Using capture-recapture over a year, we analyzed the influence of habitat type (forest and nonforest) and season (rainy and dry) on variation in ASR, male aggregation and the trajectory movement of 2 dung beetle species with different life history traits: Deltochilum mexicanum (a hornless roller species) and Dichotomius satanas (a tunneler species with horns on its head and thorax). We found opposite tendencies. The D. mexicanum population tends to be female-biased, but the population of D. satanas tends to be predominantly male, and observed values were not related to habitat type or season. However, the 95% confidence intervals estimated were highly variable between seasons depending on habitat. On examining the monthly variation in ASR for both habitats, we found that it depends on the species. In addition, male aggregation differed between species depending on habitat type and season, and species movement patterns were closely related to their habitat preferences. Based on our results, we argue that comparative population studies of species with different life history traits are necessary to understand the variation in demographic parameters as well as its ecological and evolutionary implications in the face of spatial and climatic environmental variation.

Relevance of the Cell Neighborhood Size in Landscape Metrics Evaluation and Free or Open Source Software Implementations

Landscape metrics constitute one of the main tools for the study of the changes of the landscape and of the ecological structure of a region. The most popular software for landscape metrics evaluation is FRAGSTATS, which is free to use but does not have free or open source software (FOSS). Therefore, FOSS implementations, such as QGIS’s LecoS plugin and GRASS’ r.li modules suite, were developed. While metrics are defined in the same way, the “cell neighborhood” parameter, specifying the configuration of the moving window used for the analysis, is managed differently: FRAGSTATS can use values of 4 or 8 (8 is default), LecoS uses 8 and r.li 4. Tests were performed to evaluate the landscape metrics variability depending on the “cell neighborhood” values: some metrics, such as “edge density” and “landscape shape index”, do not change, other, for example “patch number”, “patch density”, and “mean patch area”, vary up to 100% for real maps and 500% for maps built to highlight this variation. A review of the scientific literature was carried out to check how often the value of the “cell neighborhood” parameter is explicitly declared. A method based on the “aggregation index” is proposed to estimate the effect of the uncertainty on the “cell neighborhood” parameter on landscape metrics for different maps.