Effects of risks of sperm competition on the numbers of eupyrene and apyrene sperm ejaculated by the moth Plodia interpunctella (Lepidoptera: Pyralidae)

This study examines the effects of different risks of sperm competition upon ejaculate characteristics in the moth Plodia interpunctella. In this short-lived species, females will remate and thus generate sperm competition, while males have a limited sperm supply. We therefore predict males to have evolved prudence in ejaculate allocation and investigate the effects of (1) rival male presence, (2) female mating history and (3) female age, upon the ejaculation of eupyrene (fertilizing) and apyrene (non-fertile) sperm numbers. We found no effect of the presence of rival males upon ejaculate characteristics, and conclude, due to the mating system of P. interpunctella, that rival males do not represent a proximate risk of sperm competition. We controlled female mating history by allowing females to receive different and predictable numbers of sperm which they then store for at least 7 days. In subsequent matings (7 days later) we found that new males ejaculated significantly more eupyrene sperm to females that had previously received larger numbers of sperm. We conclude that males increase numbers of eupyrene sperm to maintain success in sperm competition with rival sperm already in storage in the female. We found no effect of female mating history upon the ejaculation of apyrene sperm. Female age, however, had a significant negative effect upon both sperm types. We discuss these results in relation to sperm competition theory and apyrene sperm function.     

The relationship between conspecific superparasitism and the outcome of in vitro contests staged between different larval instars of the solitary endoparasitoid Venturia canescens

When endoparasitoid wasps oviposit into hosts which have already been parasitized (= superparasitism), this results in potentially lethal interlarval competition. For solitary species, the decision to lay additional eggs should therefore be based on the probability of superparasite survival in any superparasitized host. In this study, in vitro contests staged between three larval instars of Venturia canescens Grav. (Hymenoptera: Ichneumonidae) reveal that the age difference between competitors affects the outcome of interlarval competition. Three parameters were used to assess parasitoid performance: the number of fights initiated, the number of bites inflicted, and the duration of each bite. When fighting takes place between two first instars, then both competitors were found to be evenly matched. However, at greater age differences, first-instar competitors appeared to win more fights than their larger second instar rivals. The advantage shown by younger competitors is most pronounced in contests staged between first and third instar larvae. These findings are consistent with the increasingly high levels of conspecific superparasitism shown by V. canescens in the first 5 days after initial host attack, suggesting that this parasitoid can deploy her use of deliberate superparasitism in an adaptive way. Received: 13 December 1995/Accepted after revision: 5 March 1996     

Competition between the Rotifers Brachionus patulusand Euchlanis dilatata:Effect of Algal Food Level and Relative Initial Densities of Competing Species

We tested the effect of different algal (Chlorella vulgaris) levels and inoculation densities on the outcome of competition between the rotifers Euchlanis dilatata and Brachionus patulus. The experiment was performed in 36 transparent jars, each with 20 ml of a test medium. We used three Chlorella levels: 0.75 × 10⁶, 1.5 × 10⁶, and 3.0 × 10⁶ cells/ml. For each algal level, we used five different ratios of initial inoculation density. The population growth experiments were terminated after 19 days. Regardless of inoculation densities, an increase in food level resulted in an increased population abundance of both rotifer species. Regardless of food concentration,E. dilatatawas able to outcompete B. patulus at all inoculation densities when grown together. However, when Chlorella was offered in low concentration and there was a higher ratio of Brachionus to Euchlanis at the onset of the experiment, both rotifer species coexisted in more or less equal densities until the end of the experiments. When the food level was enhanced, E. dilatata totally eliminated B. patulus. The rate of population growth ranged from 0.002 to 0.578 for B. patulus and from 0.006 to 0.447 for E. dilatata. The results are discussed with respect to the factors influencing the outcome of competition between species.     

Female ornamentation and territorial conflicts in collared flycatchers (Ficedula albicollis)

Female ornaments in species with conventional sex roles often indicate individual quality, but the evolutionary forces maintaining them are less clear. Sexual competition for breeding opportunities may represent an important role for female signals, especially in polygynous species, but there is little experimental evidence for this. The wing patch size (WPS) of female collared flycatchers indicates age and body condition and predicts social mating patterns. We challenged nest-building females with decoy females of varying WPS and found that the aggressive response of residents increased with decoy WPS, suggesting a role for this female ornament in territorial competition. Our results explain why female WPS predicts territorial distances when mated to a polygynous male and indicate that the role of WPS in female competitive interactions is similar to that in males of the same population.     

环境服务业核心竞争力研究——以城市污水处理服务业为例

环境服务业对于减轻环境污染、改善生态环境、促进环境与经济、社会协调发展具有重要意义。研究建立了环境服务业核心竞争力评价指标体系．对11个污水处理厂开展调研研究．运用层次分析法评价污水处理服务业的核心竞争力,旨在为提高环境服务业的社会经济和环境综合效益提供理论借鉴。     

2种潮间带大型海藻种间竞争作用对UV-B辐射增强的响应

选择2种代表性的潮间带大型海藻孔石莼(Ulva pertusa)和蜈蚣藻(Grateloupia filicina),采用单独培养和共同培养的方法,以生物量为主要测定指标,研究了二者种间竞争关系及这种关系在UV-B辐射增强时的响应趋势.结果表明,孔石莼和蜈蚣藻二者的种间竞争同时包含营养竞争和相生相克2种机制,试验中营养充足及营养限制的共养处理下孔石莼特定生长率是蜈蚣藻相应值的2.54和2.47倍,蜈蚣藻在竞争关系中处于劣势;UV-B辐射对单独培养的孔石莼和蜈蚣藻的生长均有抑制作用,且随着UV-B胁迫时间延长及辐射剂量的增加,抑制作用愈加显著;共同培养条件下,低剂量[1.6kJ·(m2·d)-1]、中剂量[4.8kJ·(m2·d)-1]的UV-B辐射时孔石莼虽占据竞争优势,但其种群竞争能力有弱化趋势,孔石莼和蜈蚣藻的生物量比共养对照分别下降6.81%、3.88%和10.47%、6.98%,二者的种间竞争趋向均衡;12d时高剂量[9.6 kJ·(m2·d)-1]UV-B辐射使孔石莼的生物量下降13.09%,而蜈蚣藻生物量降低更多达14.72%,从而导致孔石莼在高剂量辐射处理中的优势地位更趋于明显,因此UV.B辐射增强可改变共培养体系中孔石莼和蜈蚣藻种间竞争的关系,且对应于不同uV-B辐射剂量其表现不同;长期UV-B辐射可能会影响孔石莼和蜈蚣藻产生克生物质的代谢过程.     

竞争条件下光照对两种淡水藻生长的影响

研究了铜绿微囊藻与斜生栅藻在单种和三种配比(10:1、1:1、1:10)共同培养条件下,不同的光照强度对其生长的影响,计算了不同培养体系中两种藻的磷吸收半饱和常数。结果表明:单独培养时,铜绿微囊藻在3000lx获得最大增长率,而斜生栅藻在5000lx时增值最快;共同培养时,两种藻的生长速率相对单独培养条件下均有不同程度的下降,两种藻之间存在着互相的竞争抑制作用;在10:1共培养条件下,栅藻对微囊藻的抑制作用超过了微囊藻对栅藻的抑制作用;在1:1和1:10共培养条件下,光强低于6600lx时,微囊藻对栅藻的抑制作用相对于栅藻对微囊藻的抑制作用更大。从光吸收半饱和常数看,微囊藻的光吸收的半饱和常数总是小于栅藻,可见微囊藻对光更具亲和性。总体上看,较低光照下,微囊藻的竞争能力强于栅藻,微囊藻竞争成为优势种具有较高的概率;而光照强度较大时,栅藻竞争成为优势种具较高的概率。     

2,2’,4,4’—四溴联苯醚对2种赤潮微藻种间竞争的影响

基于Logistic种群增长模型,研究了2,2’,4,4’—四溴联苯醚(BDE-47)的亚急性毒性胁迫对不同初始接种生物量比的赤潮异弯藻(Heterosigmaakashiwo)和米氏凯伦藻(Kareniamikimotoi)种间作用的影响.结果发现:不同的初始接种生物量比影响微藻间的竞争.加入0.05、0.25 mg/LBDE-47后,对于K. mikimotoi而言,不同初始生物量比的处理组表现出高浓度组的最大环境容纳量、种群瞬时增长率均大于低浓度组(P<0.05),而H. akashiwo高浓度组的最大环境容纳量、种群瞬时增长率均小于低浓度组(P<0.05).微藻之间的竞争表现出向着对K. mikimotoi有益方向发展的规律,因此一定浓度下的BDE-47干扰了两种微藻之间的竞争.     

Occurrence of the non-native annual bluegrass on the Antarctic mainland and its negative effects on native plants

Few non-native species have colonized Antarctica, although increased human activity and accelerated climate change may increase their number, distributional range, and effects on native species on the continent. We searched 13 sites on the maritime Antarctic islands and 12 sites on the Antarctic Peninsula for annual bluegrass (Poa annua), a non-native flowering plant. We also evaluated the possible effects of competition between P. annua and 2 vascular plants native to Antarctica, Antarctic pearlwort (Colobanthus quitensis) and Antarctic hairgrass (Deschampsia antarctica). We grew the native species in experimental plots with and without annual bluegrass under conditions that mimicked the Antarctic environment. After 5 months, we measured photosynthetic performance on the basis of chlorophyll fluorescence and determined total biomass of both native species. We found individual specimens of annual bluegrass at 3 different sites on the Antarctic Peninsula during the 2007-2008 and 2009-2010 austral summers. The presence of bluegrass was associated with a statistically significant reduction in biomass of pearlwort and hairgrass, whereas the decrease in biomass of bluegrass was not statistically significant. Similarly, the presence of bluegrass significantly reduced the photosynthetic performance of the 2 native species. Sites where bluegrass occurred were close to major maritime routes of scientific expeditions and of tourist cruises to Antarctica. We believe that if current levels of human activity and regional warming persist, more non-native plant species are likely to colonize the Antarctic and may affect native species.     

Definition and calculation of uncertainty in ecological process models

We present a method of multi-criteria assessment for the analysis of process model uncertainty that combines analysis of model structure, parameters and data requirements. There are three components in calculation and definition of uncertainty.

(1)

Assessment criteria: Uncertainty in a process model is reduced as the model can simultaneously simulate an increased number of assessment criteria selected to test specific aspects of the theory being investigated, and within acceptable limits set for those criteria. This reduces incomplete specification of the model—the characteristic that a model may explain some, but not all, of the observed features of a phenomenon. The calculation required is computation of the Pareto set which provides the list of simultaneously achieved criteria within specified ranges.