Differential effects of interspecific interactions and water availability on survival, growth and fecundity of three congeneric grassland herbs

Fitness of individual plants and of populations depends on the rates of survival, growth and fecundity. This study tested whether vital rates were differentially affected by biotic interactions and water availability. The effects of manipulations of above-ground competition (through clipping) and water availability (through water addition) on the vital rates of seedlings of three species (Viola elatior Fries, Viola pumila Chaix and Viola stagnina Kit.) were analysed in dry, mesic and wet grasslands. Water addition and grassland type had the largest effects on survival (accounting for 41 and 24% of total variation, respectively) across species. Height growth rate was positively affected by grassland type (19%) and water addition (12%) and varied among species (8%), while leaf accumulation rates and reproduction were affected by grassland type and clipping. The data suggested facilitative effects of the canopy on seedling survival in the dry grassland. This study presents evidence that environmental conditions and biotic interactions may have differential effects on seedling survival, growth and reproduction. The findings highlight the complex interplay between spatial and temporal environmental variation and biotic interactions in structuring plant communities.     

Ethanol production in multistage continuous, single stage continuous, Lactobacillus-contaminated continuous, and batch fermentations

Saccharomyces cerevisiae-based ethanol fermentations were conducted in batch culture, in a single stage continuous stirred tank reactor (CSTR), a multistage CSTR, and in a fermentor contaminated with Lactobacillus that corresponded to the first fermentor of the multistage CSTR system. Using a glucose concentration of 260 g l^–1 in the medium, the highest ethanol concentration reached was in batch (116gl^–1), followed by the multistage CSTR (106gl^–1), and the single stage CSTR continuous production system (60gl^–1). The highest ethanol productivity at this sugar concentration was achieved in the multistage CSTR system where a productivity of 12.7gl^–1h^–1 was seen. The other fermentation systems in comparison did not exceed an ethanol productivity of 3gl^–1h^–1. By performing a continuous ethanol fermentation in multiple stages (having a total equivalent working volume of the tested single stage), a 4-fold higher ethanol productivity was achieved as compared to either the single stage CSTR, or the batch fermentation.     

Effect of age on reproductive attributes of an aphidophagous ladybird, Cheilomenes sexmaculata

The effect of both male and female age was investigated on certain reproductive attributes, viz. mating incidence, mating duration, fecundity, percent egg viability, ratio of reproductive and non‐reproductive periods and reproductive rate, of an aphidophagous ladybird, Cheilomenes sexmaculata (Fabricius). Females started mating at the age of 8 hours post‐emergence (PE) and males at the age of 2 days PE. Mating in the laboratory was a male‐dominated phenomenon. The mating duration and reproductive rate of 10‐day‐old females when mated with males of varying ages increased up to the male age of 60 days, and thereafter decreased, whereas, fecundity, egg viability and ratio of reproductive and non‐reproductive periods increased up to the male age of 50 days, and thereafter declined. However, when females of varying ages were mated with 10‐day‐old males, fecundity and reproductive rate increased up to 40 days of female age, respectively, then decreased. The ratio of reproductive and non‐reproductive periods increased with increasing age of females. Mating age for optimal reproductive output was 10J50‐day‐old males and NE to 40‐day‐old females. Reproductive cessation in males was recorded after 50 days PE, whereas in females at the age of 40 days PE. Higher mating durations lead to elevated reproductive rates. Delay in the reproductive phase was positively correlated with longevity. The results of this study may aid mass multiplication of this ladybird by identifying and promoting usage of adults of optimal age. Our results also enhance our understanding of the effect of age on reproductive attributes in ladybirds.     

疟疾媒介斯氏按蚊印度品系经溴氰菊酯或溴氰菊酯增效剂选择后的繁殖劣势

了解敏感和抗性蚊虫的繁殖适合度对于规划和实施蚊虫防治计划具有重要意义。本研究分别将斯氏按蚊Anopheles stephensi幼虫用溴氰菊酯(AnD_L)及溴氰菊酯和PBO混配制剂(1∶5) (AnD_P), 或斯氏按蚊成虫用溴氰菊酯(AnD_A) 进行选择后, 在实验室内检测了起源于印度德里的斯氏按蚊亲本（AnS）和抗性品系 (AnR) 的繁殖适合度的变化,从繁殖力、生育力、卵孵化率和生殖营养周期的长度等方面评价了斯氏按蚊的繁殖适合度。结果表明：与AnS品系相比, AnR品系的生殖营养周期缩短了60%~73%。与AnS品系相比, AnR品系的产卵量显著降低, 降幅达14.5%~37.9%,对溴氰菊酯抗性最强的AnD_L40品系的产卵量降低得最多。这些结果说明溴氰菊酯抗性与繁殖劣势之间可能存在正相关。与亲本品系相比, AnD_L40品系的卵孵化率降低了19.4%~30.9%, 进一步证实了这一相关性。在RD_P品系中观察到繁殖适合度降低, 表明溴氰菊酯增效剂的选择不仅在降低溴氰菊酯抗性水平而且在降低抗性个体频率上的效率。在对溴氰菊酯几乎不具有抗性的成虫品系的选择中繁殖适合度降低, 暗示溴氰菊酯作为灭杀斯氏按蚊成虫剂的效果要好于作为杀幼虫剂的效果。这些结果提示, 通过对斯氏按蚊实施不同抗性治理策略, 种群中抗性基因型的繁殖适合度的降低可消除杂合子和抗性纯合子。     

Birth-death symmetry in the evolution of a social trait

Studies of the evolution of a social trait often make ecological assumptions (of population structure, life history), and thus a trait can be studied many different times with different assumptions. Here, I consider a Moran model of continuous reproduction and use an inclusive fitness analysis to investigate the relationships between fecundity or survival selection and birth-death (BD) or death-birth (DB) demography on the evolution of a social trait. A simple symmetry obtains: fecundity (respectively survival) effects under BD behave the same as survival (respectively fecundity) effects under DB. When these results are specialized to a homogeneous population, greatly simplified conditions for a positive inclusive fitness effect are obtained in both a finite and an infinite population. The results are established using the elegant formalism of mathematical group theory and are illustrated with an example of a finite population arranged in a cycle with asymmetric offspring dispersal.     

温湿度对桃小食心虫成虫生殖力的影响

在实验室内观察研究桃小食心虫Carposina niponensis Walsingham越冬代成虫在一系列温度和湿度下的生殖能力。结果表明,环境温度和相对湿度显著影响食心虫成虫寿命、交尾和产卵。从19℃到29℃,雌成虫寿命随温度升高而缩短。适宜成虫交尾和产卵的温度为23～26℃,相对湿度为80%～100%。     

Females Remate for Sperm Replenishment in a Seed Bug: Evidence from Offspring Viability

Females of many insects mate multiply but why they do so remains controversial. Here we investigated the effects of multiple matings on female reproductive success of a New Zealand seed bug, Nysius huttoni. We found little evidence for females to gain material (nutritional) benefits through multiple matings because the number of matings did not have significant effect on female fecundity. Females remated to the same males or different males produced similar number of viable offspring, suggesting that females do not obtain genetic benefit from remating in terms of offspring viability. With the increase of the number of matings, however, overall fertility rate significantly increased and daily fertility rate declined significantly slower over time. These results suggest that females remate for the replenishment of sperm. Five matings are sufficient for females to maximize their reproductive success, and additional matings appear to be superfluous. However, the females of this bug mate as many as 68 times if males and females are paired for lifetime. This can be explained by the convenience hypothesis, i.e., females remate superfluously to minimize the costs of harassment by promiscuous males.     

High productivity of human recombinant beta-interferon from a low-temperature perfusion culture

Recombinant human interferon-beta (β-IFN), used in the therapeutic treatment of multiple sclerosis (MS), can be produced on a large-scale from genetically engineered Chinese hamster ovary (CHO) cells. However, its hydrophobicity causes non-reversible, molecular aggregation in culture. The parameters affecting aggregation were determined to be concentration, culture residence time, temperature and glycosylation. Although the protein can be produced in Escherichia coli in a non-glycosylated form, the addition of glycans confers a reduced rate of aggregation as well as a 10-fold higher bioactivity. We report on the application of a low temperature perfusion culture designed to control the parameters that cause aggregation. In this three-phase culture system there is a transition to a low temperature (32°C) in a batch mode prior to implementing perfusion at 1 volume/day using an acoustic cell separator. Perfusion at the low temperature resulted in a 3.5-fold increase in specific productivity and a 7-fold increase in volumetric productivity compared to the batch culture at 37°C. The percentage aggregation of β-IFN was reduced from a maximum of 43% in batch culture to a minimum of 5% toward the end of the perfusion phase. The glycosylation profile of all samples showed predominantly sialylated biantennary fucosylated structures. The extent of sialylation, which is important for bioactivity, was enhanced significantly in the perfusion culture, compared to the batch culture.     

Experimental observations on maternal reproductive rate and offspring characteristics

Starting from a clone of Philodina roseola (Rotifera, Bdelloidea) six homogeneous animals have been reared. From them three different age cohorts have been studied in order to determine their life tables. Cohorts and parental life schedules are compared and discussed. A sort of correlation between offspring fecundity and life span and maternal rate of egg production could be established.     

饲粮蛋白质水平对蜂群繁殖性能的影响

本试验旨在研究饲料蛋白质水平对蜜蜂产浆期繁殖性能的影响。选择35群群势、蜂王年龄和质量一致的意大利蜜蜂Apis mellifera L.,随机分为7组,分别饲喂蛋白质水平为15%、20%、25%、30%、35%及40%的试验饲粮并以油菜花粉作为对照,测定各组蜂群的繁殖性能。结果表明,试验前期,饲粮蛋白质水平对蜂群群势有显著性影响,然而在试验中后期,则无显著影响(P>0.05);随着饲粮蛋白质水平的增加,蜂王产卵力和工蜂初生重呈先升高后降低的变化趋势,与对照组相比差异不显著(P>0.05)。