Evolutionary importance of parental care performance,food resources,and direct and indirect genetic effects in a burying beetle

Indirect genetic effects (IGE) of parental care performance and the direct–indirect covariance contribute substantially to total heritability in domesticated and laboratory mammals. For animals from natural populations empirical estimates of IGE are sparse. Thus, despite recent models relating IGE to evolution, evolutionary interpretations of IGE are limited. To address this deficit, we used a reciprocal cross‐fostering breeding design to estimate environmental influences, direct and indirect genetic effects, and direct–indirect genetic covariances in the burying beetle Nicrophorus pustulatus to determine the evolutionary importance of IGE arising from variation in parental care performance. Carrion size positively affected adult mass and time on carrion, but had no effect on total development time. Males were slightly larger than females. For both mass and development, independent of these environmental influences, direct and indirect genetic effects were of moderate magnitude. Total genetic effects explained 36–50% of the phenotypic variance in mass and size and 27–37% of phenotypic variance in development time. Direct–indirect genetic covariances were zero or close to zero. Thus, for both mass and development time, the response to natural selection arising from environmental variation may be accelerated by the presence of IGE in N. pustulatus. The generality of this pattern and the evolutionary significance of IGE arising from parental care awaits further study of natural populations.     

Relative herbivory tolerance and competitive ability in two dominant : subordinate pairs of perennial grasses in a native grassland

We evaluated herbivory tolerance and competitive ability within twodominant : subordinate pairs of C₄, perennial grasses at each of twosites to determine the contribution of these processes to herbivore-inducedspecies replacement. Herbivory tolerance was assessed by cumulative regrowthfrom defoliated plants of each species and competitive ability was evaluated byrelative uptake of a ¹⁵N isotope placed into the soil between pairedspecies in the field. Herbivory tolerance was similar for the dominant andsubordinate species in both plant pairs and defoliation intensity had a greaterinfluence on herbivory tolerance than did defoliation pattern. Both specieswithin the Sorghastrum nutans : Schizachyriumscoparium pairs exhibited comparable nitrogen acquisition from a¹⁵N enriched pulse with or without defoliation. In contrast,S. scoparium acquired more ¹⁵N than did itssubordinate neighbor, Bothriochloa laguroides when thisspecies pair was undefoliated. Uniform defoliation of this species pair at adefoliation intensity removing 70% of the shoot mass accentuated this responsefurther demonstrating the greater competitive ability of the dominant comparedto the subordinate species. Although the 90% defoliation intensity reducednitrogen acquisition by the dominant relative to the subordinate species,B. laguroides, it did not reduce nitrogen acquisition bythe dominant below that of the subordinate neighbor. The occurrence of similarherbivory tolerance among dominant and subordinate species indicates thatselective herbivory suppressed the greater competitive ability, rather than thegreater herbivory tolerance, of the dominant grasses in this experimentaldesign. These data suggest that interspecific competitive ability may be ofequal or greater importance than herbivory tolerance in mediatingherbivore-induced species replacement in mesic grasslands and savannas.     

Density-dependent accumulation of phase characteristics in a natural population of the desert locust Schistocerca gregaria

Abstract. Phase characteristics of locusts from parents that experienced different population densities were investigated under field conditions in Morocco. The density experienced by adults induced a marked phase change in colour, behaviour and morphometry of their offspring. A high-density subpopulation gave rise to a preponderance of black hatchlings that exhibited a high level of aggregation as later stage nymphs and showed gregarious morphometric features as adults, whereas a low-density subpopulation produced a majority of green hatchlings with a lesser tendency to group as final-instar nymphs and more solitarious morphometry as adults. The constrained isolation of insects from the low-density subpopulation, or crowding of insects from the high-density subpopulation, resulted in a behavioural and morphometric change towards even more solitarious characteristics in the former and more pronounced gregarious characteristics in the latter, relative to field-caught insects of the same age. These results from the field are consistent with those in the laboratory and provide more evidence for the dual roles of an individual locust's experience of crowding as well as that of its parents in density-dependent phase change.     

Simulation analysis to test the influence of model adequacy and data structure on the estimation of genetic parameters for traits with direct and maternal effects

Simulations were used to study the influence of model adequacy and data structure on the estimation of genetic parameters for traits governed by direct and maternal effects. To test model adequacy, several data sets were simulated according to different underlying genetic assumptions and analysed by comparing the correct and incorrect models. Results showed that omission of one of the random effects leads to an incorrect decomposition of the other components. If maternal genetic effects exist but are neglected, direct heritability is overestimated, and sometimes more than double. The bias depends on the value of the genetic correlation between direct and maternal effects. To study the influence of data structure on the estimation of genetic parameters, several populations were simulated, with different degrees of known paternity and different levels of genetic connectedness between flocks. Results showed that the lack of connectedness affects estimates when flocks have different genetic means because no distinction can be made between genetic and environmental differences between flocks. In this case, direct and maternal heritabilities are under-estimated, whereas maternal environmental effects are overestimated. The insufficiency of pedigree leads to biased estimates of genetic parameters.     

Hormonal Correlates of Maternal Style in Captive Macaques (Macaca fuscata and M. mulatta)

Previous studies on nonhuman primate maternal styles showed that variation in infant-directed behavior falls along two dimensions, traditionally labeled as protectiveness and rejection. We investigated maternal styles in rhesus (Macaca mulatta) and Japanese (M. fuscata) macaques living in analogous captive social groups, and correlated them with the levels of estrogen metabolites excreted in female feces during the perinatal period. We focally observed mother-infant pairs 3 hours per week during the first 12 weeks of infant life. We collected fecal samples twice a week from each mother, starting 4 weeks before delivery and ending 4 weeks after delivery. Three significant components were extracted by principal component analysis from 15 different infant directed behaviors, each reflecting a different aspect of mothering style: rejection is correlated with behavioral measures of maternal opposition to contact; protectiveness is correlated with maternal solicitude; and independence is correlated with time in contact, grooming and cradling. Levels of estrogen metabolites are significantly correlated to rejection but not to protectiveness or independence, indicating that, in nonhuman primates, individual endocrine changes related to maternal behavior might specifically affect the timing of contact interruption.     

Nutritional status of the Indian population

High prevalence of low birth weight, high morbidity and mortality in children and poor maternal nutrition of the mother continue to be major nutritional concerns in India. Although nationwide intervention programmes are in operation over two decades, the situation has not changed greatly. In addition, the Indian population is passing through a nutritional transition and is expected to witness higher prevalences of adult non-communicable diseases such as diabetes, hypertension and coronary heart disease according to the theory of ‘fetal origin of adult disease’. Clearly, there is a need for examining several issues of nutritional significance for effective planning of interventions. In particular, maternal nutrition and fetal growth relationship, long term effects of early life undernutrition, interactions of prenatal nutritional experiences and postnatal undernutrition are some of the major issues that have been discussed in the present paper with the help of prospective data from various community nutrition studies carried out in the department.     

Additive main effect and multiplicative interaction model for a diallel-cross analysis

Diallel mating designs have proved informative in determining the inheritance of quantitative traits of interest to plant breeders. Apart from the well-established analyses of a complete diallel, the two-way factorial data structure of this design lends itself to analysis by the additive-main-effects-and-multiplicative-interaction (AMMI) model. This research article describes the joint application of the AMMI model and Griffing’s method 1, model I, to gain insight into the breeding value of inbred lines in a self-pollinated crop such as disomic, hexaploid bread wheat. Data from a multi-environment trial of a complete diallel cross between eight lines adapted to the East African highlands were analyzed to provide an example of this joint analysis. This combined approach identified not only the direction of a cross, i.e. which parent should be male or female, but also which crosses produce offspring showing F₁ heterosis. Received: 10 June 2000 / Accepted: 31 July 2000     

半干旱区春小麦品种竞争能力与产量关系的研究

 采用de Wit替代系列法研究了黄土高原半干旱雨养农业区传统地方品种(和尚头)与现代品种(陇春8275)之间在混播条件下的竞争结局。在单播条件下现代品种较之地方品种具有更高的产量;但在混播条件下,和尚头具有明显的竞争优势。本项研究结果说明竞争优胜者并非是单播条件下产量性能更佳的品种,即作物品种的竞争能力与生产性能之间存在着负相关关系。形成这种关系的主要原因在于作物群体内个体竞争选择的方向与人类农业生产追求的目标不一致。     

Reproductive biology of the andromonoecious shrub Trevoa quinquenervia (Rhamnaceae)

Various aspects of the reproductive biology of the andromonoecious shrub Trevoa quinquenervia Gill. & Hook, were studied in a population located in central Chile. Flowering extends from mid August to the end of December. The small, white, entomophilous flowers are incompletely protandrous and last c. 5 days. A weak, pleasant odour along with nectar and pollen attracts 17 diurnal insect species, seven of which are probable pollinators: these include Diptera (Syrphidae and Bombyliidae), Hymenoptera (Apidae and Colletidae) and Coleoptera (Melyridae). Besides perfect flowers T. quinquenervia individuals possess c. 10% staminate flowers, which are lighter, seem to be shorter-lived, and show a smaller gynoecium with abnormal ovules. Reproduction is exclusively sexual and apparently xenogamous, with pollen transfer depending on insect vectors. Although flower morphology and individual flower phenology do not fully prevent self-pollination (and geitonogamy can easily take place) the level of autogamy is low. Therefore, some self-incompatibility mechanism seems operative in this species. Fruit set of open-pollinated flowers is 6.6%, and ripe fruits contain on average 0.66 viable seeds. Predispersal (maternal) reproductive success (percent ovules becoming viable seeds) is 1.45%. For medium to full-sized individuals this corresponds to c. 2600 to 8600 potential offspring per year. Beyond the production of male flowers, four other aspects of the species' reproductive biology seem directed to enhance pollen export, partly implying increased male allocation: (a) a high pollen:ovule ratio, (b) protection of anthers against pollen-robbing by means of the cucullate petals, (c) secondary pollen presentation in a hairy barrier located above the nectary, and (d) a reduction in female allocation achieved by the regular abortion of two out of the three ovules in each ovary, thus producing a mostly one-seeded fruit provided with a thin, energy-poor pericarp. It is proposed that the advantages of enhanced pollen flow for a self-incompatible organism, which is moreover structured in isolated populations, might explain the increased male effort, including the joint evolution of andromonoecy and one-seededness.