Sex ratios under asymmetrical local mate competition in the parasitoid wasp Nasonia vitripennis

Sex ratio theory has proved remarkably useful in testing theadaptive nature of animal behavior. A particularly productivearea in this respect is Hamilton's theory of local mate competition(LMC), which has been extended in numerous directions to includegreater biological realism, allowing more detailed tests inspecific organisms. We have presented one such extension, termedasymmetrical LMC, which occurs when egg laying by females ona patch is asynchronous, and emerging males do not disperse,resulting in the extent of LMC on a patch varying over time.Our aim here is to test whether the parasitoid wasp Nasoniavitripennis responds to variation in the degree of asymmetricalLMC. Specifically, we show that females adjust their offspringsex ratios in response to (1) variation in the amount of asynchronyin emergence between broods on a patch and (2) the number andproportion of previously parasitized hosts on the patch. Ourresults provide qualitative support for the predictions of theory,suggesting new levels of complexity in the sex ratio behaviorof this much-studied organism. However, our results do not alwaysprovide quantitative support for theory, suggesting furthercomplexities that must be clarified.     

Contrasting patterns in elevational diversity between microorganisms and macroorganisms

Aim Data and analyses of elevational gradients in diversity have been central to the development and evaluation of a range of general theories of biodiversity. Elevational diversity patterns have, however, been severely understudied for microbes, which often represent decomposer subsystems. Consequently, generalities in the patterns of elevational diversity across different trophic levels remain poorly understood. Our aim was to examine elevational gradients in the diversity of macroinvertebrates, diatoms and bacteria along a stony stream that covered a large elevational gradient. Location Laojun Mountain, Yunnan province, China. Methods The sampling scheme included 26 sites spaced at elevational intervals of 89 m from 1820 to 4050 m elevation along a stony stream. Macroinvertebrate and diatom richness were determined based on the morphology of the specimens. Taxonomic richness for bacteria was quantified using a molecular fingerprinting method. Over 50 environmental variables were measured at each site to quantify environmental variables that could correlate with the patterns of diversity. We used eigenvector‐based spatial filters with multiple regressions to account for spatial autocorrelation. Results The bacterial richness followed an unexpected monotonic increase with elevation. Diatoms decreased monotonically, and macroinvertebrate richness showed a clear unimodal pattern with elevation. The unimodal richness pattern for macroinvertebrates was best explained by the mid‐domain effect (r² = 0.72). The diatom richness was best explained by the variation in nutrient supply, and the increase in bacterial richness with elevation may be related to an increased carbon supply. Main conclusions We found contrasting patterns in elevational diversity among the three studied multi‐trophic groups comprising unicellular and multicellular aquatic taxa. We also found that there may be fundamental differences in the mechanisms underlying these species diversity patterns.     

Noni as an anxiolytic and sedative: A mechanism involving its gamma-aminobutyric acidergic effects

Noni (Morinda citrifolia) is increasing in worldwide popularity as a food or dietary supplement with versatile health benefits. The aim of this study was to investigate the effects of Noni fruit on anxiety symptoms in vitro. To this end, a competitive GABAa receptor-binding assay was developed. Our preliminary study indicates that the methanol crude extract of Noni fruit showed significant affinity to the gamma-aminobutyric acid A (GABAa) inhibitory neurotransmitter receptors, and displayed 75% binding inhibition of the agonist radioligand [3H] muscimol at a concentration of 100 microg/ml. Further experiments demonstrated that the MeOH extract, and its BuOH and H2O partitions, exhibited IC50 values of 22.8, 27.2, and 17.1 microg/ml, respectively, in the GABAa-binding assay. Experimental results with Noni fruit indicate the presence of competitive ligand(s), which may bind to the GABAa receptor as an agonist, and thus induce its anxiolytic and sedative effects. The study provides an in vitro rationale for one of Noni's versatile and traditional uses. In addition, an HPLC fingerprint profile of the methanolic extract of Noni fruit has been established for quality control purpose.