Smaller species experience mild adversity under shading in an old‐field plant community

Plant competition experiments commonly suggest that larger species have an advantage, primarily in terms of light acquisition. However, within crowded natural vegetation, where competition evidently impacts fitness, most resident species are relatively small. It remains unclear, therefore, whether the size advantage observed in controlled experiments is normally realized in habitats where competition is most intense. We characterized the light environment and tested for evidence of a size advantage in competition for light in an old‐field plant community composed of perennial herbaceous species. We investigated whether larger species contributed to reduced light penetration (i.e., greater shading), and examined the impact of shade on smaller species by testing whether their abundance and richness were lower in plots with less light penetration. Light penetration in plots ranged from 0.3% to 72.4%. Significant effects were more common when analyses focused on small plants that reached reproduction (i.e., flowering rooted units); focusing on only flowering plants (i.e., excluding nonflowering rooted units) can clarify community patterns. Plots with a greater mean species height had significantly lower light penetration, and plots with lower light penetration had significantly lower flowering abundance and richness of small species. However, the impact of shade on the flowering abundance and richness of small species was relatively small (R ² values between 8% and 15%) and depended on how we defined “small species.” Synthesis: Our results confirm that light penetration in herbaceous vegetation can be comparable to levels seen in forests, that plots with taller species cast more shade, and that flowering smaller species are less abundant and diverse in plots where light penetration is low. However, variation in mean plot height explained less than 10% of variation in light penetration, and light penetration explained between 5 and 15% of variation in the flowering abundance and richness of small species. Coupled with the fact that flowering small species were present even within the most heavily shaded plots, our results suggest that any advantage in light competition by large species is limited. One explanation is that at least some small species in these communities are shade‐tolerant. Shade tolerance in predominantly herbaceous communities, particularly among small plant species, requires further research.     

Estimating the impact of oyster restoration scenarios on transient fish production

Oyster reef restoration projects are increasing in number both to enhance oyster density and to retain valuable ecosystem services provided by oyster reefs. Although some oyster restoration projects have demonstrated success by increasing density and biomass of transient fish, it still remains a challenge to quantify the effects of oyster restoration on transient fish communities. We developed a bioenergetics model to assess the impact of selected oyster reef restoration scenarios on associated transient fish species. We used the model to analyze the impact of changes in (1) oyster population carrying capacity; (2) oyster population growth rate; and (3) diet preference of transient fish on oyster reef development and associated transient fish species. Our model results indicate that resident fish biomass is directly affected by oyster restoration and oyster biomass, and oyster restoration can have cascading impacts on transient fish biomass. Furthermore, the results highlight the importance of a favorable oyster population growth rate during early restoration years, as it can lead to rapid increases in mean oyster biomass and biomass of transient fish species. The model also revealed that a transient fish's diet solely dependent on oyster reef‐derived prey could limit the biomass of transient fish species, emphasizing the importance of habitat connectivity in estuarine areas to enhance transient fish species biomass. Simple bioenergetics models can be developed to understand the dynamics of a system and make qualitative predictions of management and restoration scenarios.     

红眼突变灰飞虱的生物学特性和交配优势

灰飞虱Laodelphax striatellus是我国重要水稻害虫之一, 表型变异可能影响灰飞虱的配偶选择性和种群特性。本实验采用生命表构建法研究了红眼突变灰飞虱的繁殖力、 内禀增长率等种群生命参数, 然后以1红眼雌虫、 1红眼雄虫和1纯合黑眼雄虫（♀rr×♂rr♂BB）或1红眼雄虫、 1红眼雌虫和1纯合黑眼雌虫（♀rr♀BB×♂rr）配对模式以及不同比例红眼成虫群体配对模式研究红眼突变对灰飞虱交配竞争力的影响。结果表明红眼突变灰飞虱除若虫死亡率（17.1%）显著高于正常个体（10.3%） (P<0.05)外, 其他生物学指标如繁殖力、 卵孵化历期、 若虫发育历期、 成虫寿命、 内禀增长率等与正常个体无显著差异。但红眼突变对灰飞虱配偶选择性有一定的影响。♀rr×♂rr♂BB和♀rr♀BB×♂rr组合F1代红眼和黑眼分离比例卡方试验值为18.15和14.99, 大于理论值。当红眼与黑眼个体以2︰8比例配对时, 红眼灰飞虱雄虫存在交配优势, 其后代红眼个体数大于期望值。这些结果为进一步研究灰飞虱红眼突变机理和利用红眼基因标记研究灰飞虱遗传分化奠定了基础     

The essential role of sodium bioenergetics and ATP homeostasis in the developmental transitions of a cyanobacterium

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Predation of perch on vendace larvae: diet composition in an oligotrophic lake and digestion time of the larvae

The diet of perch Perca fluviatilis was studied to reveal possible predation on vendace Coregonus albula larvae in an oligotrophic lake. Perch diet changed with the size of the fish: small perch ate mainly zooplankton and the diet shifted more to benthic invertebrates and fishes in larger perch. There were also annual and spatial differences in the diet, probably reflecting differences in the availability of prey animals. Perch predation on vendace larvae was only observed in the area with high availability of the larvae. The result suggested strengthened predation when the density of the larvae increases. According to bioenergetics modelling, the perch population increased natural mortality of vendace larvae only marginally. Food intake of spawning female perch was slightly reduced, whereas spawning males fed similarly to non-spawning males. Hence, the spawning period of perch was only a minor refuge for vendace larvae. Laboratory experiments of perch digestion rate demonstrated that, due to rapid digestion of the small fish larvae, diet sampling interval should not be >2 h in the field.     

Defective Mitochondrial Pyruvate Flux Affects Cell Bioenergetics in Alzheimer’s Disease-Related Models

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Telemetry tags increase the costs of swimming in northern fur seals,Callorhinus ursinus

Animal‐borne instruments have become a standard tool for collecting important data from marine mammals. However, few studies have examined whether placement of these data loggers affects the behavior and energetics of individual animals, potentially leading to biasing data. We measured the effect of two types of relatively small data loggers (<1% of animals’ mass and front profile) on the swimming speeds and energy expenditure of four female northern fur seals (Callorhinus ursinus) while swimming at depth. Swim speeds and rates of oxygen consumption were measured as the trained fur seals repeatedly swam an underwater circuit, with or without the tags. We found the placement of either tested tag significantly affected both the behavior and energetics of the fur seals in our study. Diving metabolic rate increased an average of 8.1%–12.3% (depending on tag type) and swim speed decreased an average of 3.0%–6.0% when wearing the tags. The combined changes in velocities and metabolic rates resulted in a 12.0%–19.0% increase in the total energy required by the fur seals to swim a set distance. The demonstrated effects of tags on behavior and energy expenditure may bias data sets from wild animals and potentially incur longer‐term impacts on the studied animals.     

Food consumption and faecal deposition of plant nutrients by black swans (Cygnus atratus Latham) in a shallow New Zealand lake

Deposition of faeces by black swans (Cygnus atratus Latham) feeding on benthic algae in a shallow New Zealand lake was determined by collection of faeces from the lake bottom and from the shore. The two methods showed good agreement after adjustment for the weight loss on immersion. The mean daily faecal output per swan was 52 g dry weight. The nitrogen content of the faeces averaged 2.3% of dry weight, and was dominated by soluble organic nitrogen (59% of total N). Phosphorus averaged 0.44% of dry weight, with 66% of it being particulate, and 30% soluble reactive phosphorus. Although faecal inputs of total phosphorus were sufficient to generate concentrations of 15–30 mg m^–3, the faecal contributions of both N and P were only a minor component of the fluctuations observed in the lake, and were also small in relation to the total nutrient pool in the water and benthic algae. Waterfowl faeces appear to have low ratios of N to P, which will favour dominance of the phytoplankton by cyanobacteria in lakes where the faecal component of nutrient loads is large. The few data available suggest that the nitrogen content of waterfowl faeces is largely independent of that in their food. Food consumption, calculated by using cellulose as an indigestible faecal marker, was 104 g dry weight swan^–1 d^–1, a figure that appears low in relation to those for other swan species. Even the highest published figure for food intake by a swan is only about one half of the corresponding average metabolically-adjusted figures for geese, and we caution against the uncritical use of bioenergetic models for determining rates of food consumption and defaecation.     

Frequency dependent selection: I. Rare male phenomenon in D. subobscura dependent on the proportion of Amy genotypes and substrate composition

Analysis of the rare male mating advantage in D. subobscura, as a type of frequency dependent selection on maltose and starch media, was done by applying different statistical approaches (χ², cross-product ratio, variance and regression analysis). They reveal that mating occurs at random when proportions of prospective mates are equal, and that mating success of the males homozygous for Amy-locus genotypes (S/S and F/F) depends on their proportion. Regression analysis showed that the F/F males are sexually more active (have higher vigour) than S/S males. Rare male effect is one-sided and appears in F/F males that partake in more heterogamic matings. Comparison of the number of observed and expected homo- and heterogamic matings shows that homogamic matings are more frequent. Multifactorial analysis of variance shows that the number of matings are different for nine pairs of lines and four possible mating types (S_fS_m, S_fF_m, F_fS_m, F_fF_m). The rare male phenomenon is not dependent on different food composition, but is associated with variations in individual genotypes.