The ageing trajectory (trend in ageing) and reproduction-longevity trade-off in both sexes of the ladybird Propylea dissecta were studied. The ageing trajectories of both sexes were investigated in terms of reproductive performance, using initial oviposition (egg laying within 24 h of mating) acting as an indicator of the effect of female age and initial viability (percentage of eggs laid within 24 h of mating that hatched) of the effect of male age. Ageing trends were sex dependent, with reproductive performance declining later in females than in males. Initial oviposition of females was largely age dependent and the initial viability of males was age dependent but less so than for females. There is a strong trade-off between number of matings and longevity. Statistical analyses reveal that this trade-off results from an early onset of mortality rather than an increase in mortality rate. A minimum lifespan was observed in this ladybird beyond which the longevity did not further decline.
The theory of planned behaviour (TPB) is a widely used theory in behavioural analysis. It incorporates social, cultural, psychological and economic approaches into behavioural analysis. The authors of the theory of reasoned action and its extension, the theory of planned behaviour have recommended that it is appropriate to conduct an elicitation study to identify the final sets of salient beliefs in the TPB analysis. Even though the TPB is based on salient beliefs, researchers have paid less attention in this regard. In order to identify final set of salient beliefs for TPB analysis, Ajzen and Fishbein (1980) have suggested three rules. This paper compares the three rules suggested by Ajzen and Fishbein (1980) and an alternative approach was suggested. The paper analyses the beliefs of farmers in Sri Lanka in respect to the decision to adopt new technology. The findings showed that the three rules suggested by Ajzen and Fishbein (1980), lead to different sets of salient beliefs for TPB analysis. Therefore, an alternative approach was suggested which is a trade-off between salient beliefs that fall into the final set and beliefs that are foregone. The suggested approach is strengthen by computing the product of the “belief strength” and “outcome evaluation” (expectancy value method) for each belief mentioned. It provides more accurate index for eliciting the most significant salient beliefs for TPB analysis.
Foraging and bedding sites are key ungulate demands of their habitats. Research however, on the differences between these two types of sites has been neglected. This study deals with the winter foraging and bedding site selection of the Asiatic ibex (Capra sibirica) in the Tianshan Mountains in the Xinjiang Uyghur Autonomous Region, China. A total of twelve line-transects were used to assist research of the Asiatic ibex within five valleys and canyons during December of 2010 and January of 2011. Ninety-five bedding and one hundred foraging sites used by the Asiatic ibex were examined and the effects of fifteen different environmental factors on habitat selection were analyzed and evaluated in this study. In comparison with its bedding sites, the Asiatic ibex in winter showed a greater preference for semi-shady slopes and higher vegetation density in its selection of foraging sites. Regarding its foraging site preferences when compared to its bedding site preferences, this species was less sensitive to deeper and greater snow cover, to a lower hiding cover level, and to greater
distances from the nearest escape structures. Stepwise Discriminant Analysis showed that a group of five environmental factors played a dominant role in bedding and foraging site preferences. These factors were, in the order of their contribution value: vegetation density, hiding cover level, distance from the top of the mountain, and distance from escape structures. Using these five environmental factors alone, the ability to accurately predict bedding and foraging site preferences of the Asiatic ibex reached 93.3 %.
Plant invasions may be limited by low radiation levels in ecosystems such as forests. Lantana camara has been classified among the world's 10 worst weeds since it is invading many different habitats all around the planet. Morphological and physiological responses to different light fluxes were analyzed. L. camara was able to acclimate to moderately shaded environments, showing a high phenotypic plasticity. Morphological acclimation to low light fluxes was typified by increasing leaf size, leaf biomass, leaf area index and plant height and by reduced stomatal density and leaf thickness. Plants in full sunlight produced many more inflorescences than in shaded conditions. Physiological acclimation to low radiation levels was shown to be higher stomatal conductance, higher net photosynthetic rates and higher efficiency of photosystem II (PSII). L. camara behaves as a facultative shade-tolerant plant, being able to grow in moderately sheltered environments, however its invasion could be limited in very shady habitats. Control efforts in patchy environments should be mainly directed against individuals in open areas since that is where the production of seeds would be higher and the progress of the invasion would be faster. and J. Carrión-Tacuri ... [et al.].
The trade-off between flight capability and reproduction is well known in adult males of insects with wing dimorphism but the reproductive advantage of short-winged (SW) males over long-winged (LW) males appears to vary across insect taxa. In the present study, we determined the difference in the mating ability of SW and LW males of Velarifictorus ornatus (Orthoptera: Gryllidae) in order to evaluate whether the SW male morph has a reproductive advantage. We found that the choice of a mate depended on the female. Compared with LW males, SW males had an obvious mating advantage when both SW and LW males courted females simultaneously, and that dealation significantly enhanced the mating ability of LW males. Losing the ability to produce songs reduced the mating advantage of SW males, thereby indicating that the greater mating advantage of SW males was related to the attractiveness of the song. In addition, the difference in the mating ability of LW and SW males was not related to body size or age. These results indicate that SW males of V. ornatus have a mating advantage over their LW counterparts because their underdeveloped flight muscles allow them to devote more resources to reproduction., Lv-Quan Zhao, Huai-Lin Chai, Hong-Jun Wu, Dao-Hong ZhuU., and Obsahuje bibliografii
Closely related species can be used for studying the ecological significance of their traits. The response in terms of survival, clonal growth and vegetative and generative characteristics of three related Myosotis species to competition and soil characteristics were studied in a three year pot experiment. Plants from four populations per species were cultivated in a factorial combination of substrate (nutrient-rich soil and mixtures with sand) and competition (with or without Holcus lanatus) treatments. Survival, clonal growth and the majority of the growth characteristics of all three Myosotis species were reduced by competition. The effect of substrate was less pronounced, and variable for various traits: the soil with sand mixture was more suitable for survival, clonal growth and seed germination whereas in the nutrient-rich soil plants were taller, but this effect was modified by competition. The differences among species corresponded well to expectation based on their known habitat preferences. Myosotis caespitosa, a species typical of short-term habitats such as emerged bottoms of ponds, exhibited the shortest life span and was also the most sensitive to competition: all plants of this species died in the competition treatment before the end of the second season. Nevertheless, the surviving plants (in the no-competition treatment) were able to form several daughter rosettes or stolons; some of them spread clonally till the third year. Myosotis palustris subsp. laxiflora, which inhabits the banks of rivers and brooks often disturbed by torrential floods, survived best and had the highest potential for clonal growth and spreading. Most plants of this species produced rhizomes and stolons and spread the furthest of all the three species. Myosotis nemorosa, which lives mostly in meadows, the most stable habitat of the studied congeners, but also a habitat with a strongly competitive matrix of species, was intermediate in terms of survival, and clonal growth, forming mainly short rhizomes. This species exhibited the highest among-population variability in all recorded characteristics, which might be due to its local adaptation to a wide spectrum of habitats. We argue that the details of prevailing disturbance regime, rather than some general disturbance intensity explain the clonal behaviour of the species compared.
Life-history theory predicts trade-offs between resources invested in reproduction and other fitness-related traits. To date, most studies have focused on potential reproductive trade-offs in females. However, it is now generally accepted that reproduction is also costly for males, and thus males too may be subject to trade-offs. We examined the relationship between development time and the production of both fertile and non-fertile sperm in males of the African bush brown butterfly (Bicyclus anynana) selected for short or long pre-adult development time. Fast developing males ejaculated fewer non-fertile sperm on their first mating, suggesting that there could be a trade-off between ejaculate production and development time in this species. Contrary to predictions, slow developing males were smaller, produced fewer fertile sperm and took longer to mate. We discuss why this might be the case, and suggest that there may be a cost to the production of non-fertile sperm in the Lepidoptera.
Typically, the relationship between insect development and temperature is described by two characteristics: the minimum temperature needed for development to occur (Tmin) and the number of day degrees required (DDR) for the completion of development. We investigated these characteristics in three English populations of Thrips major and T. tabaci [Cawood, Yorkshire (N53°49', W1°7'); Boxworth, Cambridgeshire (N52°15', W0°1'); Silwood Park, Berkshire (N51°24', W0°38')], and two populations of Frankliniella occidentalis (Cawood; Silwood Park). While there were no significant differences among populations in either Tmin (mean for T. major = 7.0°C; T. tabaci = 5.9°C; F. occidentalis = 6.7°C) or DDR (mean for T. major = 229.9; T. tabaci = 260.8; F. occidentalis = 233.4), there were significant differences in the relationship between temperature and body size, suggesting the presence of geographic variation in this trait. Using published data, in addition to those newly collected, we found a negative relationship between Tmin and DDR for F. occidentalis and T. tabaci, supporting the hypothesis that a trade-off between Tmin and DDR may constrain adaptation to local climatic conditions.
A short-winged morph, whose occurrence is controlled by a simple recessive Mendelian unit, was recently discovered in Locusta migratoria. The existence of trade-offs between flight capability associated with wing length and other fitness-related traits are often documented for insects. The present study investigated the evolutionary significance of the short-winged and long-winged morphs of this locust using two laboratory strains showing wing dimorphism. The life-history traits examined included nymphal development, adult body weight, percentage adult survival, age at first reproduction, egg production and hatchling body weight. The results indicate that there are no consistent morph-specific differences in any of these traits. Of the several possibilities considered, the most likely is that the short-winged morph of this locust is an aberration or represents an initial stage in the evolution of this species., Yudai Nishide, Seiji Tanaka., and Obsahuje seznam literatury
Insect dormancy responses, in the broad sense of modifications of development, are examined from a general perspective. The range of responses is extraordinarily wide because environments are diverse, different taxa have different evolutionary histories, adaptations are needed for both seasonal timing and resistance to adversity, and not only development but also many other aspects of the life-cycle must be coordinated. Developmental options are illustrated by examining the wide range of ways in which development can be modified, the fact that each individual response consists of several components, and the different potential durations of the life-cycle. The concepts of alternative life-cycle pathways (chosen according to current and likely future environmental conditions) and of active and passive default responses are treated. Also introduced are aspects of variation and trade-offs.
Some general conclusions that help in understanding dormancy responses emerge from such an examination. Many options are available (cf. Table 1). The nature of the habitat, especially its predictability, determines the potential effectiveness of many of the developmental options. Any particular set of responses reflects evolutionary history and hence depends on past as well as current environments. It is not necessarily obvious what kinds of selection, especially requirements for timing versus resistance to adversity, explain a particular life cycle. Life-cycle pathways have multiple components, so that components cannot be analyzed in isolation. A given feature, such as delayed development, can have multiple roles. Default responses can be either active (development continues unless signalled otherwise) or passive (development stops unless signalled otherwise), making necessary a broad approach to understanding the action of environmental cues. Even relatively minor effects that fine-tune dormancy responses enhance survival, but may be difficult to detect or measure. Trade-offs are not inevitable, not only when certain resources are surplus, but also because resources in very short supply (constraints) cannot be traded off. Life-cycle components are widely, but not universally, coordinated. These conclusions confirm that the range of dormancy responses is wider, more complex and more integrated than has often been recognized.