A survival-analysis-based simulation model for Russian wheat aphid population dynamics

A simulation model for Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), populations is built by integrating survival-analysis-based development and survivor functions and the same-shape reproduction distribution model in the framework of Leslie [Leslie, P.H., 1945. On the use of matrices in certain population mathematics. Biometrika 33, 183–212] matrix structure. Survival analysis is utilized to model both the development and survival of RWA populations, and the Cox (1972) proportional hazards model is fitted with the data sets from our laboratory observation of 1800 RWA individuals under 25 factorial combinations of five temperature regimes and five barley plant-growth stages. Rather than using simple age-specific survivor rates as in the traditional Leslie matrix, the survivor functions based on survival analysis describe age-specific, temperature and plant stage-dependent RWA survival probabilities. Similarly, a probability model from survival analysis to estimate the probability that an individual will reach mature adult stage is utilized to describe the development process; this makes the transition from nymphal stage to mature adult stage dependent on RWA age as well as temperature and plant-growth stage.Inspired by the same-shape distribution and rate-summation approach for modeling insect development, a similar approach for modeling insect reproduction under variable temperature is developed. This new same-shape reproduction distribution model incorporates individual variation in reproduction capability, as well as the effects of RWA age, temperature and plant-growth stage. Consequently, the same-shape reproduction distribution model replaces the simple age-specific fecundities in Leslie matrix model. To the best of our knowledge, this work is the first to introduce survival analysis to simulation modeling in entomology and ecology and also the first to integrate our newly developed same-shape reproduction distribution model into application.     

Effects of Self-Compatibility on the Distribution Range of Invasive European Plants in North America

Abstract:  Many plant species have been introduced to new continents, but only a small subset of these have become invasive. It has been predicted that self-compatible species, particularly those that do not need the services of pollinators, are more likely to establish and spread after long-distance dispersal. We tested whether this hypothesis, commonly called Baker's law, applies to 361 species that have invaded the United States from Europe. Species capable of autonomous seed production occurred in significantly more states than species requiring a pollen vector. Moreover, of the species that are not capable of autonomous seed production, self-compatible species occurred in significantly more states than those that are not self-compatible. The positive effect of autonomous seed production on the range of invasion was larger for abiotically pollinated species than for biotically pollinated species and for monocarpic species than for polycarpic species. These results support Baker's law, and we recommend that screening protocols for predicting invasiveness of species considered for introduction should include assessment of their breeding system.     

Nestmate recognition for eggs in the honeybee (<Emphasis Type="Italic">Apis mellifera</Emphasis> L.)

Colony integrity is fundamental to social insects and is threatened by the reproduction of non-nestmates. Therefore, discrimination between eggs derived from nestmates and non-nestmates would constitute an adaptation to prevent exploitation of the entire cooperative group by unrelated individuals. The removal of nestmate and non-nestmate queen and worker-laid eggs was evaluated in honeybees using colonies of Apis mellifera capensis to test female and of A. m. scutellata to test male eggs. The data show that honeybees can distinguish between nestmate and non-nestmate eggs of both sexes. Moreover, non-nestmate female queen-laid eggs were removed significantly faster than nestmate female worker-laid eggs in A. m. capensis, indicating that nestmate recognition cues can override caste-specific ones. While the experimental manipulation accounts for 37.2% (A. m. scutellata) or 1.6% (A. m. capensis) of variance in relation to egg removal, nestmate recognition explains 33.3% for male eggs (A. m. scutellata) and 60.6% for female eggs (A. m. capensis), which is almost twice as high as the impact of caste (16.7% A. m. scutellata; 25% A. m. capensis). Our data show a stronger effect of nestmate recognition on egg removal in the honeybee, suggesting that cues other than caste-specific ones (viability/kin) can dominate egg removal behavior. In light of intraspecific social parasitism, preventing the reproduction of unrelated individuals (group selection) rather than preferring queens’ eggs (kin selection) appears to be the driving force behind the evolution of egg removal behavior in honeybees.     

Effects of reproduction on the antipredator tactics of snakes (Tropidonophis mairii, Colubridae)

Does an animal’s reproductive state influence the distance at which it flees from an approaching predator? We predicted that reproduction would increase approach distances in pregnant females (because they are burdened with eggs and thus less able to escape rapidly), but reduce them in males (because of lower vigilance due to males focusing on mate-searching rather than predator detection). Field data on approach distances of keelback snakes (Tropidonophis mairii, Natricinae, Colubridae) supported both of these predictions. We walked the same 1.3-km transect along a dam wall in tropical Australia on 135 nights, and recorded the distances at which snakes fled from our approach. Locomotor speeds were measured for a subset of these animals. Variations in approach distance due to season, weather conditions, prior capture history and snake body size were minor, but reproduction strongly affected approach distances for snakes of both sexes. Gravid females were slower than non-gravid females, and fled at greater distances. Reproductive status did not affect locomotor speeds of males, but males that were reproductive (i.e., contained sperm) permitted closer approach than did non-reproductive adult males. Reproduction thus affected approach distances in snakes of both sexes, but in opposite directions and for different reasons.     

Differential reproductive success among subfamilies in queenless honeybee (<Emphasis Type="Italic">Apis mellifera</Emphasis> L.) colonies

With very rare exceptions, queenright worker honeybees (Apis mellifera L.) forego personal reproduction and suppress reproduction by other workers, preferring to rear the queens sons. This is in stark contrast to colonies that have lost their queen and have failed to rear a replacement. Under these conditions workers activate their ovaries and lay many eggs that develop parthenogenetically into a final brood of males (drones) before the colony perishes. Interestingly, not all workers contribute equally to this final generation of drones in queenless colonies. Some subfamilies (workers that share the same father) contribute a disproportionately greater number of offspring than other subfamilies. Here we explore some of the mechanisms behind this reproductive competition among subfamilies. We determined the relative contribution of different subfamilies present in colonies to laying workers, eggs, larvae and pupae by genotyping samples of all life stages using a total of eight microsatellite loci. Our colonies were headed by free-mated queens and comprised 8–17 subfamilies and therefore differed significantly from colonies used in an earlier study investigating the same phenomena where colonies comprised an artificially low number of subfamilies. We show that, first, subfamilies vary in the speed with which they activate their ovaries after queen-loss and, second, that the survival of eggs to the larval stage is unequal among subfamilies suggesting that some subfamilies lay eggs that are more acceptable than others. However, there is no statistically significant difference among subfamilies in the survival of larvae to pupae, indicating that ovary activation and egg survival are the critical components to reproductive competition among subfamilies of queenless honeybee workers.Communicated by R. Page     

微尾鼩种群繁殖的年龄和季节特征

2003年9月～2004年8月对四川南充地区微尾鼩种群不同年龄组繁殖的差异以及各年龄组在不同季节的差异进行研究.结果表明,微尾鼩总性比为1.05,经χ2检验,两性差异不显著,繁殖个体性比为1.08,两性差异不显著.雄性微尾鼩1、2月份各年龄组的睾丸大小(长径与短径)和重量差异不显著,3～12月份差异极显著.微尾鼩各年龄组睾丸大小和重量在12mo内季节变化为1、2月差异均不明显,3～12月份未成体组(Ⅰ)季节变化明显,而成体Ⅰ组(Ⅱ)和成体Ⅱ组(Ⅲ)差异不明显.雌性子宫斑数在1～10之间,平均胎仔数为4.05±0.14只(N=76),4、9月份为繁殖高峰期,繁殖指数分别为2.37和1.45,4～10月份成体Ⅰ组(Ⅱ)和成体Ⅱ组(Ⅲ)的繁殖力和平均胎仔数年龄差异不明显,成体Ⅱ组(Ⅲ)繁殖力和平均胎仔数在4～12月份季节变化不显著.1、2月份均为雌雄微尾鼩非繁殖期,3～12月份为繁殖期.表2参24     

Changes in life histories of cladocerans (Cladocera) from the rotifer-mediated allelochemicals

ABSTRACT

We hypothesised that at higher densities herbivorous rotifers through their allelochemicals affect the survival and reproduction of cladocerans. To test this, we separately cultured three rotifers (Brachionus calyciflorus, Brachionus havanaensis, and Plationus patulus) and three cladocerans (Ceriodaphnia dubia, Daphnia pulex, and Moina macrocopa). Chlorella vulgaris was used as food and reconstituted moderately hard water was used as medium. The conditioned-medium (CM) obtained from each of rotifer species was used to conduct cohort life table tests of cladocerans. SDS PAGE electrophoresis revealed the molecular weights of proteins present in the rotifer conditioned medium were 55–63?kDa. Compared to C. dubia and D. pulex, Moina was more resistant to rotifer-mediated chemicals. Gross reproductive rate of C. dubia was significantly stimulated by the rotifer-CM. However, gross and net reproductive rates of D. pulex were strongly reduced (72–85%) due to P. patulus-CM but not from the other two rotifer species. The rate of population increase of M. macrocopa was significantly reduced by the rotifer CM. Overall, about 46% (adverse effect: 24%; stimulatory impact: 22%) of the life history variables in controls significantly differed from rotifer-CM treatments, thus proving our hypothesis that rotifer-mediated allelochemicals had some effect on the cladoceran life history variables.     

我国大麻哈鱼资源及其保护途径

大麻哈鱼是我国黑龙江和吉林两省特产的经济鱼类，近２０年来资源明显衰退．本文根据多年一系列实地调查研究，论述了目前我国境内３种大麻哈鱼的自然分布、经济价值、资源特征与现状，分析了资源衰退原因及其开发利用中所存在的问题，初步提出资源保护途径。