定量评价天敌控害功能的生态能学方法

由于昆虫的能量完全来自于寄主,因此昆虫摄入的能量相当于食物的被取食消耗量。生态能量学方法的基本原理就是捕食性天敌完全依靠捕食猎物(害虫)而获取能量。显然,捕食性天敌摄入的能量就相当于为猎物(害虫)的被捕食消耗量,也即是捕食性天敌摄入量等于猎物(害虫)的被捕食消耗量。由此,可通过研究捕食性天敌和害虫种群的能量动态,定量分析捕食性天敌对害虫的控制作用。本文详细论述了生态能量学方法的基本原理、测算方法,并以棉田捕食性瓢虫类捕食作用为例,介绍了该方法的应用,为定量评价天敌的控害作用提供了一种新方法。     

Empirical analysis of the influence of swimming pattern on the net energetic cost of swimming in fishes

We tested the hypothesis that the energetics of swimming in a flume accurately represent the costs of various spontaneous movements using empirical relationships between fish swimming costs, weight, and speed for three swimming patterns: (1) 'forced swimming' corresponded to movements adopted by fish forced to swim against a unidirectional current of constant velocity; (2) 'directed swimming' was defined as quasi-rectilinear movements executed at relatively constant speeds in a stationary body of water and (3) 'routine swimming' was characterized by marked changes in swimming direction and speed. Weight and speed explained between 76% (routine swimming) and 80% (forced swimming) of net swimming cost variability. Net costs associated with different swimming patterns were compared using ratios of model predictions (swimming cost ratio; SCR) for various weight and speed combinations. Routine swimming was the most expensive swimming pattern (SCR for routine and forced swimming =6.4 to 14.0) followed by directed (SCR for directed and forced swimming =0.9 to 2.8), and forced swimming. The magnitude of the difference between the net costs of forced and spontaneous swimming increases with movement complexity and decreases as fish weight increases.     

The energetic cost of various behaviors in the laboratory mouse

The continuous 12-hr observation of a mouse placed in a respiratory chamber has made it possible to record the succession of behaviors of the animal, as well as the associated variations of CO2 concentrations in the chamber. Ten behaviors have been considered; these included rest, locomotion, sniffing, feeding, drinking, nest building and various types of grooming. These data have been used for the estimation, by means of Kalman filtering, of the energetic cost of each behavior. Thus, at 20 degrees C, these costs vary between 1.51 ml CO2/g/hr (rest) and 4.90 ml CO2/g/hr (locomotion). These costs seem independent of any underlying biological rhythm; they yield basal metabolic estimates and average daily metabolic rates similar to those found in the literature. The low energetic cost of each behavioral bout, as compared to the daily energy intake of the mouse, leads one to believe that the behavioral transitions of this animal are not to be ascribed to energetical reasons. These results have been validated with data obtained from two other mice under similar conditions.     

Orangutans use compliant branches to lower the energetic cost of locomotion

Within the forest canopy, the shortest gaps between tree crowns lie between slender terminal branches. While the compliance of these supports has previously been shown to increase the energetic cost of gap crossing in arboreal animals (e.g. Alexander 1991 Z. Morphol. Anthropol. 78, 315-320; Demes et al. 1995 Am. J. Phys. Anthropol. 96, 419-429), field observations suggest that some primates may be able to use support compliance to increase the energetic efficiency of locomotion. Here, we calculate the energetic cost of alternative methods of gap crossing in orangutans (Pongo abelii). Tree sway (in which orangutans oscillate a compliant tree trunk with increasing magnitude to bridge a gap) was found to be less than half as costly as jumping, and an order of magnitude less costly than descending the tree, walking to the vine and climbing it. Observations of wild orangutans suggest that they actually use support compliance in many aspects of their locomotor behaviour. This study seems to be the first to show that elastic compliance in arboreal supports can be used to reduce the energetic cost of gap crossing.     

The energetic cost of reproductive conflicts in the ant Pachycondyla obscuricornis

In a variety of social animals, individuals can secure reproductive rights through aggressive dominance. Direct individual benefits of aggression are widely recognized, but underlying costs affecting group productivity, and thus indirect benefits, are less clear. Costs of aggressive regulation of reproduction are especially important in small social insect colonies, where individual workers could potentially dominate male production. We estimated the energetic costs associated with the regulation of worker reproduction in the ponerine ant Pachycondyla obscuricornis, using the total CO2 emission of a colony as a measure. The level of CO2 emission of 12 experimental colonies varied significantly during five periods with varying levels of aggression and egg-laying. Overall, CO2 emission increased with the degree of fighting in a colony, but was not associated with differences in egg-laying. Aggressive regulation of reproduction and the formation of a dominance hierarchy thus pose an energetic cost to the colony. Furthermore, workers reduce their work-activities immediately after experimental orphaning, giving a further cost to the colony. These costs might influence the outcome of conflicts over male production in ants. This paper presents the first quantification of energetic costs of aggressive behavior regulating reproduction in ants.     

The effect of size on the optimal shapes of gliding insects and seeds

Conventional aerodynamic arguments suggest that possession of high aspect ratio wings will always improve the flight performance of glides. Drag and power will be minimized at intermediate flight speeds. It is shown, however, that as the aspect ratio increases, these minimum drag speeds are reduced, and will fall below the stall speed of the glider. This will happen at lower aspect ratios in small gliders, which operate at higher profile drag coefficients. Increasing the aspect ratio further will improve performance less than this analysis suggests.
A detailed analysis is developed to calculate the optimum shape of small gliders. Profile drag increases with aspect ratio, owing to the fall in the Reynolds number, while induced drag falls with increasing aspect ratio. Minimum drag will be encountered and hence the glide angle will be minimized at intermediate values of aspect ratio. Best glide angles are achieved at low speeds (high lift coefficients) and the optimum aspect ratio increases with the mass of the glider.
Small natural gliders possess large, low aspect ratio wings. The aspect ratios are generally somewhat below those which would produce the best glide angle at stall speed, but should give a reasonable performance over a range of speeds.     

Currencies for foraging based on energetic gain

We carry out a theoretical investigation of the behavior of a foraging animal that maximizes either the net amount of energy obtained (self-feeding) or the amount of energy delivered to another animal such as its young or to a store (provisioning). Using an novel graphical approach, we derive general results concerning the effects of constraints on the amount of energy the animal can spend or acquire. In the context of an animal that is provisioning, that is, both feeding itself and delivering energy to a given location, we establish a general relationship between the best foraging option when feeding itself and the best option to use when delivering energy. Our results extend and unify previous results in this area.     

Does the strength of an immune response reflect its energetic cost?

The energetic cost of immune responses has been proposed to be an important basis for trade-offs between life-history traits, such as between survival and reproduction. A critical assumption of this hypothesis is that the magnitude of the energetic cost increases with the strength of an immune response, so that energy can be saved by partly suppressing a response. Here, we test this assumption experimentally. The immune system of great tits Parus major was experimentally activated by injecting different doses of phytohemagglutinin (PHA) in the wing web. We found the resting metabolic rate of immune challenged birds to increase by 5%. However, although great tits injected with a high dose had a stronger immune response, this was not paralleled by a higher metabolic rate. Thus, we found the energetic cost of the immune response to be relatively low and not dose-dependent. This suggests to us that the energetic cost of immune responses cannot form the basis for trade-offs between life-history traits.     

Characterizing the cost of oviposition in insects: a dynamic model

The development of a consensus model of insect oviposition has been impeded by an unresolved controversy regarding the importance of time costs versus egg costs in mediating the trade-off between current and future reproduction. Here I develop a dynamic optimization model that places time and egg costs in a common currency (opportunity costs expressed as decreased lifetime reproductive success) so that their relative magnitudes can be compared directly. The model incorporates stochasticity in host encounter and mortality risk as well as behavioral plasticity in response to changes in the age and egg load of the ovipositing female. The dynamic model's predictions are congruent with those of a simpler, static model: both time- and egg-mediated costs make important contributions to the overall cost of oviposition. Modest quantitative differences between the costs predicted by the static versus dynamic models show that plasticity of oviposition behavior modulates the opportunity costs incurred by reproducing females. The relative importance of egg-mediated costs increases substantially for oviposition events occurring later in life. I propose that the long debate over how to represent the cost of oviposition should be resolved not by advocating the pre-eminence of one sort of cost above all others, but rather by building models that represent the complementary roles of different costs. In particular, both time and egg costs must be recognized to produce a general model of insect oviposition that incorporates a realistic representation of the cost of reproduction. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effects of obesity and sex on the energetic cost and preferred speed of walking.

The metabolic energy cost of walking is determined, to a large degree, by body mass, but it is not clear how body composition and mass distribution influence this cost. We tested the hypothesis that walking would be most expensive for obese women compared with obese men and normal-weight women and men. Furthermore, we hypothesized that for all groups, preferred walking speed would correspond to the speed that minimized the gross energy cost per distance. We measured body composition, maximal oxygen consumption, and preferred walking speed of 39 (19 class II obese, 20 normal weight) women and men. We also measured oxygen consumption and carbon dioxide production while the subjects walked on a level treadmill at six speeds (0.50-1.75 m/s). Both obesity and sex affected the net metabolic rate (W/kg) of walking. Net metabolic rates of obese subjects were only approximately 10% greater (per kg) than for normal-weight subjects, and net metabolic rates for women were approximately 10% greater than for men. The increase in net metabolic rate at faster walking speeds was greatest in obese women compared with the other groups. Preferred walking speed was not different across groups (1.42 m/s) and was near the speed that minimized gross energy cost per distance. Surprisingly, mass distribution (thigh mass/body mass) was not related to net metabolic rate, but body composition (% fat) was (r2= 0.43). Detailed biomechanical studies of walking are needed to investigate whether obese individuals adopt novel energy saving mechanisms during walking.     

Oviposition pattern of phytophagous insects: on the importance of host population heterogeneity

Frequency distributions of insect immatures per host are often fitted to contagious distributions, such as the negative binomial, to deduce oviposition pattern. However, different mechanisms can be involved for each theoretical distribution and additional biological information is needed to correctly interpret the fits. We chose the chestnut weevil Curculio elephas, a pest of the European chestnut Castanea sativa, as a model to illustrate the difficulties of inferring oviposition pattern from fits to theoretical distributions and from the variance/mean ratio. From field studies over 13–16 years, we show that 20 out of the 31 yearly distributions available fit a negative binomial and 25 a zero-inflated Poisson (ZIP). No distribution fits a Poisson distribution. The ZIP distribution assumes heterogeneity within the fruit population. There are two categories of host: the first comprises chestnuts unsuitable for weevil oviposition or in excess relative to the number of weevil females, and the second comprises suitable fruits in which oviposition behavior is random. Our results confirm this host heterogeneity. According to the ZIP distribution, the first category of hosts includes on average 74% of the chestnuts. A negative binomial distribution may be generated by either true or false contagion. We show that neither interference between weevil females, nor spatial variation in the infestation rate exist. Consequently, the observed distributions of immatures are not the result of false contagion. Nevertheless, we cannot totally exlude true contagion of immatures. In this paper we discuss the difficulty of testing true contagion in natural conditions. These results show that we cannot systematically conclude in favour of contagion when fitting a distribution such as the negative binomial or when a variance/mean ratio is higher than unity. Received: 22 September 1997 / Accepted: 15 December 1997     

Evidence for the entrainment of breathing by locomotor pattern in human

In human, it has been shown that interactions between locomotor and respiratory patterns may lead to locomotor-respiratory couplings termed entrainment. In order to prove that this coupling is really an entrainment, we tried to show that it obeys one of the expected rules, i.e. that it evolves and is not present for all imposed locomotor frequencies. For that purpose, seventeen healthy volunteers were asked to run on a treadmill at 14 different locomotor rates (instead of 2 or 3 in previous works) for 40 s. All the subjects did not exhibit the same coupling and different relationships could be obtained: the most commonly observed was 2:1 (2 locomotor activities for a respiratory one) but other forms could appear (4:1 and even 5:2 or 3:2). When the coupling evolution was followed in the same subject, it did not appear for all locomotor frequencies but only for locomotor periods close to harmonics of respiratory ones (absolute coordination). On both sides of these values, it progressively evolved to relative coordination and to the lack of coordination. When two forms of absolute coordination were observed in a same subject, the phase relationships followed the rules of the entrainment. Compared to data obtained in quadrupeds, these results suggest that the entrainment of breathing frequency by the locomotor activity is due to central interactions between the respiratory and locomotor pattern generators and does not depend on a chemical regulation avoided here by short locomotor sequences.     

Distribution pattern and competition of insects breeding on Camellia japonica flower

The distribution pattern and competition of insects exploiting Camellia japonica flowers were studied in Tokyo, central Japan, to understand how their distributions are determined. Dasiops sp. of Lonchaeidae (Diptera) exploited flower buds and showed random distribution, whereas Drosophila unipectinata, D. oshimai and D. lutescens of Drosophilidae (Diptera) and Epuraea commutata of Nitidulidae (Coleoptera) exploited fully opened, late and fallen flowers and showed aggregated distribution. From the distribution pattern, it is assumed that Dasiops sp. has clutches of single egg whereas drosophilid and nitidulid species have clutches of more than one egg. In resource supplementary experiments, body size of drosophilid flies increased if resources were supplemented, although their survival is assumed to be unaffected. However, their body size did not decrease with increase of larval density in resource patches. It is therefore unclear whether resource competition occurs among drosophilid flies in Camellia flowers in nature. From the present and previous studies, it is assumed that aggregation (or production of clutches of more than one egg) is related to the use of fermenting or decayed resources; aggregation might increase larval survival and/or performance under the presence of molds or microorganisms.     

StructureSelector: A web‐based software to select and visualize the optimal number of clusters using multiple methods

Inferences of population genetic structure are of great importance to the fields of ecology and evolutionary biology. The program structure has been widely used to infer population genetic structure. However, previous studies demonstrated that uneven sampling often leads to wrong inferences on hierarchical structure. The most widely used ΔK method tends to identify the uppermost hierarchy of population structure. Recently, four alternative statistics (medmedk , medmeak , maxmedk and maxmeak ) were proposed, which appear to be more accurate than the previously used methods for both even and uneven sampling data. However, the lack of easy‐to‐use software limits the use of these appealing new estimators. Here, we developed a web‐based user‐friendly software structureselector to calculate the four appealing alternative statistics together with the commonly used Ln Pr(X|K) and ΔK statistics. structureselector accepts the result files of structure , admixture or faststructure as input files. It reports the “best” K for each estimator, and the results are available as HTML or tab separated tables. The program can also generate graphical representations for specific K, which can be easily downloaded from the server. The software is freely available at http://lmme.qdio.ac.cn/StructureSelector/ .     

Reproductive success and the energetic cost of parental care in male smallmouth bass

Direct field measurements of the energetic expenditure on parental care and within-nest reproductive success of individual male smallmouth bass Micropterus dolomieui were determined by measuring the change in total body mass as well as by total body electroconductivity analysis (TOBEC™). With TOBEC, the change in total body lean mass of the same live individual was measured non-destructively at the beginning and end of the parental care period. Lean mass was the primary source of energy utilized during parental care indicating starvation and potential loss of future reproduction. Individual loss in lean mass was related positively to reproductive success suggesting that the energy expended during parental care does affect individual fitness.     

The energetic cost of the fever response in three species of ectothermic vertebrates

Three species of ectothermic vertebrates: goldfish (Carassius auratus), green tree frogs (Hyla cinerea), and desert iguanas (Dipsosaurus dorsalis) were used in this study. Metabolic rates for each species were determined at the normal afebrile preferred body temperature and at the febrile preferred body temperature or other higher body temperatures. The febrile metabolic rate (or higher rate) was significantly greater than the afebrile metabolic rate (or lower rate) in each species. The average increase in energetic cost for goldfish and desert iguana was 64.5% while the increase for the green tree frog was between 24 and 70%.     

The energetic cost of calling in the variable field cricket, Gryllus lineaticeps

Abstract. Female preferences for conspicuous male calls have been documented in many groups. However, relatively few studies have examined the metabolic costs associated with the production of call types preferred by females. We measured the oxygen consumption of calling male Gryllus lineaticeps Stål crickets using closed chamber respirometry. Calling song was recorded concurrently. The average increase in mass-specific oxygen consumption during calling was 2.7 times basal rates of oxygen consumption, and calling males consumed approximately 1.2ml O₂g^-lh^-1. Oxygen consumption increased with increasing chirp rate and pulse duration, but not with increasing chirp duration. Females of this species prefer higher chirp rates, thus some call types that increase the male's attractiveness to females require more metabolic energy to produce.