Maintenance of variance in sperm transfer rates in a scorpionfly: food availability,genetic basis,and heritability

Variation in traits closely related to fitness is expected to be low. This is because these traits are under directional selection and the best genotype should prevail. However, there have been a number of studies demonstrating the existence of considerable variance in sexually selected traits, which is generally known as the lek paradox. Accordingly, earlier studies found substantial variation in sperm transfer rates in Panorpa vulgaris. Aiming at finding the mechanism that maintains this variation, we analyzed the condition dependence and the narrow sense heritability of sperm transfer rates. Food deprivation in the larval/adult phase caused a decrease in the males’ capability of saliva secretion resulting in shorter copulations and a reduced number of transferred sperm. There was a positive correlation between mean sperm transfer rates and mean body mass. Additionally, intermale variation in sperm transfer rates decreased with increasing food availability. Hence, we suggest that sperm transfer rates in P. vulgaris are influenced by adult feeding history. Heritability analyses of sperm transfer rates did not provide significant results, which is consistent with the general hypothesis that additive genetic variance in traits closely related to fitness is small. Since a trait’s potential to respond to selection is proportional to the amount of contained additive genetic variance, the ascertained small heritability provides a satisfying explanation for the maintenance of substantial variation in sperm transfer rates.     

Suitability of Golf Course Ponds for Amphibian Metamorphosis When Bullfrogs Are Removed

Abstract:  Managing areas designed for human recreation so that they are compatible with natural amphibian populations can reduce the negative impacts of habitat destruction. We examined the potential for amphibians to complete larval development in golf course ponds in the presence or absence of overwintered bullfrog tadpoles ( Rana catesbeiana ), which are frequently found in permanent, human-made ponds. We reared larval American toads ( Bufo americanus ), southern leopard frogs ( R. sphenocephala ), and spotted salamanders ( Ambystoma maculatum ) with 0 or 5 overwintered bullfrog tadpoles in field enclosures located in ponds on golf courses or in experimental wetlands at a reference site. Survival to metamorphosis of American toads, southern leopard frogs, and spotted salamanders was greater in ponds on golf courses than at reference sites. We attributed this increased survival to low abundance of insect predators in golf course ponds. The presence of overwintered bullfrogs, however, reduced the survival of American toads, southern leopard frogs, and spotted salamanders reared in golf course ponds, indicating that the suitability of the aquatic habitats for these species partly depended on the biotic community present. Our results suggest that ponds in human recreational areas should be managed by maintaining intermediate hydroperiods, which will reduce the presence of bullfrog tadpoles and predators, such as fish, and which may allow native amphibian assemblages to flourish.     

Male moths undertake both pre- and in-copulation mate choice based on female age and weight

Variation in reproductive potential usually occurs among individuals of both sexes; for example, some individuals may carry more gametes or be able to continue to generate more gametes in their reproductive life than others. Therefore, to maximize their reproductive success, both sexes are expected to show adaptations for mate choice. However, most authors concentrated on how females choose their mates with the belief that females invest more in reproduction than males, and males are generally eager to pair with any female. In this paper, we report our work on a polygamous moth, Ephestia kuehniella Zeller (Lepidoptera: Pyralidae), with special emphasis on male pre- and in-copulation mate choice in relation to the reproductive quality and re-copulation potential of females. We show that in E. kuehniella, younger and heavier females have significantly higher reproductive value than older and lighter ones, and male sperm supply significantly decreases over successive copulations. Males exercise pre-copulation mate choice by selecting females with higher reproductive potential for copulation and in-copulation mate choice by allocating more sperm to females with higher reproductive potential. However, high-quality females are more likely to re-copulate than low-quality ones, and allocation of more sperm to females by males does not increase female reproductive outputs. It is suggested that the allocation of more sperm to high-quality females functions to increase sperm competitiveness against rivals.     

Females go where the food is: does the socio-ecological model explain variation in social organisation of solitary foragers?

The socio-ecological model (SEM) links ecological factors with characteristics of social systems and allows predictions about the relationships between resource distribution, type of competition and social organisation. It has been mainly applied to group-living species but ought to explain variation in social organisation of solitary species as well. The aim of this study was to test basic predictions of the SEM in two solitary primates, which differ in two characteristics of female association patterns: (1) spatial ranging and (2) sleeping associations. Beginning in August 2002, we regularly (re-)captured and marked individuals of sympatric populations of Madame Berthe's and grey mouse lemurs (Microcebus berthae, Microcebus murinus) in Kirindy Forest (Madagascar). We recorded data on spatial patterns, feeding and social behaviour by means of direct observation of radio-collared females. The major food sources of M. berthae occurred in small dispersed patches leading to strong within-group scramble competition and over-dispersed females with a low potential for female associations. In contrast, M. murinus additionally used patchily distributed, high-quality (large) resources facilitating within-group contest competition. The combined influence of less strong within-group scramble and contest as well as between-group contest over non-food resources allowed females of this species to cluster in space. Additionally, we experimentally manipulated the spatial distribution of food sources and found that females adjusted their spatial patterns to food resource distribution. Thus, our results support basic predictions of the SEM and demonstrated that it can also explain variation in social organisation of solitary foragers.     

Fertility signaling in queens of a North American ant

In most species of advanced eusocial insects, the partitioning of reproduction between nestmates is thought to be regulated by means of primer pheromones or other chemical cues, which presumably influence the behavior of co-queens and workers such that they maximize their own inclusive fitness. Here we show that in multi-queen colonies of the Nearctic ant, Leptothorax sp. A, physical dominance in concert with chemical cues, which signal the ovarian development of a queen, are used to control reproduction of competing queens and to influence worker behavior. The analysis of ranks obtained during two fighting periods in the annual colony cycle revealed a strong link between individual aggressiveness of a queen and her fertility. During the adoption of newly mated queens in autumn, the resident, egg-laying α-queen was more likely to start aggression first and keep her high rank position compared to the fighting period after hibernation. We suggest that this is proximately caused by the α-queen having much stronger developed ovaries in autumn than the young queens, whereas after hibernation, the ovaries of all queens are similarly inactive. Interactions during the first weeks after the end of hibernation and intrinsic, individual differences in aggressiveness appear to be crucial for the dominance rank achieved later. Queens which were allowed to become fertile when their nestmate queens still were kept under prolonged hibernation, were immediately socially dominant over the latter when all queens were reunited, though no aggression occurred. In another experiment, queen antagonism was prevented by spatial separation in different parts of the same nest and all queens began to lay eggs. Workers stayed preferentially with queens with high actual fecundity rather than with those which had had high social status before separation. This and further evidence suggest that ovarian status is communicated, most likely by a chemical cue perceived by co-queens and workers, affects the direction of their aggressive behavior, and allows them to discriminate among queens. Received: 5 May 1998 / Accepted after revision: 29 August 1998     

倒置A2/O与常规A2/O工艺除磷效果对比

通过对西安市某污水处理厂倒置A2/O工艺的沿程监测和工艺解析,分析明确了该工艺生物除磷效果差的影响因素。研究表明,缺氧池反硝化不完全,厌氧池高浓度硝酸盐是抑制聚磷菌释磷的重要因素。当厌氧池内硝酸盐浓度大于4 mg/L时会明显抑制生物除磷效果。硝酸盐的浓度在1~4 mg/L时,随着硝酸盐浓度的升高,释磷效果显著降低。为避免硝酸盐对聚磷菌的影响,需将厌氧池硝酸盐浓度控制在1 mg/L以下。硝酸盐对聚磷菌释磷的影响原因是生物脱氮除磷对碳源的竞争,以乙酸钠和原污水为碳源分析硝氮盐对释磷效果的影响。结果表明,易于生物降解的优质碳源更有利于聚磷菌在厌氧环境下释磷,倒置A2/O的前置式缺氧池首先将大量优质碳源用于反硝化,而造成后续厌氧池聚磷菌释磷效果差。针对这一研究结果,对该污水厂提出将倒置A2/O调整为常规A2/O的改造方案,改造后厌氧池硝酸盐浓度由3.57 mg/L降低至0.89 mg/L,聚磷菌释磷量提高1.8倍,系统除磷效果增强,出水总磷降低至0.66 mg/L,与倒置A2/O相比降低0.21 mg/L。     

Effects of kinship on territorial conflicts among groups of lions,<Emphasis Type="Italic"> Panthera leo</Emphasis>

Inclusive fitness theory predicts that cost of tolerant behaviour during competitive interactions is lower for relatives than for nonrelatives. Many studies have examined the effect of relatedness on behaviour within social groups. In contrast, kin selection acting among groups has received less attention. The genetic structure of African lion (Panthera leo) populations creates a strong possibility that kin selection among groups modifies behaviour during group conflicts. We used playback experiments and genetic data to investigate the importance of relatedness during simulated territorial disputes in lions. However, we found no effect of relatedness on territorial behaviour. Degree of relatedness did not affect the decision to approach simulated intrusions, nor did it affect the behaviour during approaches. The decision to approach was instead affected by position within the territory and consecutive playback number (a measure of habituation). For playbacks that did elicit an approach, the speed of response was not detectably affected by relatedness, but was affected by odds (the ratio of residents to intruders), number of intruders, number of bouts, presence of cubs, position within the territory, temperature and playback number. Although responses were unaffected by relatedness, it remains possible that other aspects of behaviour during natural encounters among prides are affected by kin selection.Communicated by L. Sterck     

Genetic analysis of parentage within experimental populations of a male dimorphic beetle,<Emphasis Type="Italic"> Onthophagus taurus</Emphasis>, using amplified fragment length polymorphism

We used the multilocus DNA fingerprinting technique, amplified fragment length polymorphism, to examine parentage of 902 offspring from eight experimental populations of the dung beetle, Onthophagus taurus. The males of this species exhibit a suit of morphological and behavioural traits that characterise alternative mating tactics. Hornless minor males sneak copulations with females that are guarded by horned major males. Our aims were to provide a prospective assessment of the potential role of frequency dependence in the maintenance of alternative mating tactics, to assess the levels of polyandry, and to determine the patterns of sperm usage by multiply mated females. The average proportion of offspring sired by major and minor males did not co-vary with the relative frequency of each morph present in experimental populations. However, there was some indication that the effective mating frequency (number of females producing offspring sired by a given male) of major and minor males may exhibit frequency dependence. Mating success of both male types declined with increasing numbers of major males. Paternity was positively associated with effective mating frequency. Females produced offspring sired from between one and eight males and, on average, paternity was distributed equally amongst a females mates, regardless of the number of males mated. Differences in fertilisation success among males were not associated with alternative male phenotypes. Neither did a males fertilisation success depend on his genetic dissimilarity with the female. These results are discussed in the context of the evolution of alternative mating strategies, and mechanisms of postcopulatory sexual selection.Communicated by N. Wedell     

Mate replacement in experimentally widowed collared flycatchers (Ficedula albicollis): determinants and outcomes

There is increasing evidence that sexual selection may be intense even in socially monogamous birds, resulting from both mate choice and sperm competition. We studied these two modes of sexual selection experimentally by removing paired male collared flycatchers, Ficedula albicollis, from their mates for 2 days and investigating the factors that influenced the likelihood of a replacement male appearing and how the removals influenced paternity. Replacement males (usually neighbouring males) appeared at 81% (n = 37) of nests where males were removed. The likelihood of this appearance was unaffected by the probable reproductive value of the female's clutch to the replacing male. A replacement was, however, less likely when the original male had a large forehead patch, a trait previously shown to be subject to sexual selection in this population. Experimental removal of males increased the level of sperm competition: 74% of experimental broods were multiply sired, compared to 29% of unmanipulated broods in a previous study. Only two factors predicted how paternity was shared between males: removed males fathered more young if removed closer to laying, and if they had larger forehead patches. The former result is consistent with last-male sperm precedence determining paternity, whereas the latter adds to other evidence that forehead patch size is the target of female preference in this species. Our results suggest that females exert some control over male replacement, and also that they may influence the fertilisation success of males by behavioural means. Received: 15 July 1998 / Received in revised form: 16 March 1999 / Accepted: 28 March 1999     

Ecological and social determinants of spacing behaviour in desert baboon groups

This paper investigates the determinants of individual spacing behaviour in a desert baboon population (Papio cynocephalus ursinus). Patterns of neighbour proximity and neighbour density were examined among adults in four groups under different ecological and social conditions (through instantaneous sampling during focal follows). Initial analysis of these data shows that (1) the use of vertical substrates (refuges such as tall trees and cliff faces) can confound patterns of spacing, and (2) individual differences in spacing can depend on the spatial scale over which it is measured. To minimise these substrate and scale effects, this analysis focuses on animals which are off refuges and examines spacing behaviour through its underlying statistical `dimensions' (identified through factor analysis). Analysis of these dimensions indicates that sex, group size, activity-habitat and female reproductive state can all have independent effects on spacing: (1) males are more dispersed than females in smaller groups, (2) male and female dispersion increases with time spent in foraging habitats, and (3) female dispersion is reduced during lactation. According to the hypotheses tested, these results indicate that feeding competition only affects spacing behaviour during foraging while predation risk plays little or no role in spacing. Most aspects of spacing behaviour are best explained by male reproductive strategies and their social repercussions. Received: 25 May 1998 / Accepted after revision: 18 July 1998