International Young Life Scientist Programme

Ａｔｔｈｅ１８ｔｈＩｎｔｅｒｎａｔｉｏｎａｌＣｏｎｇｒｅｓｓｏｆＢｉｏｃｈｅｍｉｓｔｒｙａｎｄＭｏｌｅｃｕｌａｒＢｉｏｌｏｇｙ,Ｂｉｒｍｉｎｇｈａｍ,ＥｎｇｌａｎｄＴｈｅＩｎｔｅｒｎａｔｉｏｎａｌＵｎｉｏｎｏｆＢｉｏｃｈｅｍｉｓｔｒｙａｎｄＭｏｌｅｃｕｌａｒＢｉｏｌｏｇｙ（ＩＵＢＭＢ）,ｔｈｅＦｅｄｅｒａｔｉｏｎｏｆＥｕｒｏｐｅａｎＢｉｏｃｈｅｍｉｃａｌＳｏｃｉｅｔｉｅｓ（ＦＥＢＳ）,ａｎｄｔｈｅＢｉｏｃｈｅｍｉｃａｌＳｏｃｉｅｔｙａｎｎｏｕｎｃｅｔｈｅｓｐｏｎｓｏｒｓｈｉｐｏｆａＳｙｍｐｏｓ…     

Brine Shrimp致死率生物鉴定法对八种民间药活性成分的研究

采用ＴｈｅＢｒｉｎｅＳｈｒｉｍｐＬｃｔａｌｉｔｙＢｉｏａｓｓａｙ法对民间药翼蓼ＰｔｅｒｏｘｙｇｏｎｕｍｇｉｒａｌｄｉｉＤｕｍｍｅｒｅｔＤｉｅｌｓ）,金荞麦（Ｆａｇｏｐｙｒｕｍｄｉｂｏｔｒｙｓ（Ｄ．Ｄｏｎ）Ｈａｒａ）,齿果酸模（ＲｕｍｅｘｄｅｎｔａｔｕｓＬ．）巴天酸模（ＲｕｍｅｘｐａｔｉｅｎｔｉａＬ．）网果酸模（ＲｕｍｅｘｄｉｃｔｙｏｃａｒｐｕｓＢｏｉｓｓｅｔＢｕｈｓｅ）、掌叶大黄（Ｒｈｅｕｍｐａｌ     

壁山县农田生态系统中氮肥利用与平衡的研究

壁山县农田生态系统中氮肥利用与平衡的研究何新华（云南师范大学生物系,昆明６５００９２）ＮＢａｌａｎｃｅｉｎＡｇｒｏｅｃｏｓｙｓｔｅｍｏｆＢｉｓｈａｎＣｏｕｎｔｙａｆｔｅｒＡｐｐｌｙｉｎｇＮｉｔｒｏｇｅｎｏｕｓＦｅｒｔｉｌｉｚｅｒｓ￥ＨｅＸｉｎｈｕａ（Ｄｅｐａｒｔ－ｍｅｎｔｏｆＢｉｏｌｏｇｙＹｕｎｎａｎＮｏｒｍａｌＵｎｉｖｅｒｓｉｔｙ,Ｋｕｎｍｉｎｇ,６５００９２）．ＣｈｉｎｅｓｅＪｏｕｒｎａｌｏｆＥｃｏｌｏｇｙ,１９９３,１２（５）：２９－３５。Ｔｈｅｉｎｐｕｔａｎｄｏｕｔｐｕｔｏｆｎｉｔｒｏｇｅｎａｎｄｇｒａｉｎｙｉｅｌｄｄｕｒｉｎｇ１９４９－１９８０ｉｎＢｉｓｈａｎＣｏｕｎｔｙａｒｅａｎａｌｙｓｅｄ．Ｔｈｅｒｅｓｕｌｔｓｓｈｏｗｔｈａｔｎｉｔｒｏｇｅｎｃｏｎｓｕｍｐｔｉｏｎｉｓｈｉｇｈｅｒｔｈａｎｉｔｓａｃｃｕｍｕｌａｔｉｏｎ（－３１．６％,＋１４．０％）ａｎｄｔｈｅｒａ－ｔｉｏｏｆｏｒｇａｎｉｃ－Ｎｔｏｃｈｅｍｌｃａｌ－Ｎｉｓｏｂｖｉｏｕｓｌｙｉｎｄｉｓｏｒｄｅｒ（２．００：０．６７）．Ｉｔｉｓｓｕｇｇｅｓｔｅｄｔｈａｔｎｉｔｒｏｇｅｎｂａｌ－ａｎｃｅｃａｎｂｅｍａｉｎｔａｉｎｅｄｔｈｒｏｕｇｈｐｌａ     

普通小麦基因组最可能的4个供体的ITS1和ITS2序列及其亲缘关系

对普通小麦（ＴｒｉｔｉｃｕｍａｅｓｔｉｖｕｍＬ．）基因组（ＡＡＢＢＤＤ）最可能的供体－Ｔ．ｕｒａｔｒｔｕＴｈｕｍ．（ＡＡ）、Ｔ．ｍｏｎｏｃｃｕｍｖａｒ．ｂｏｅｏｔｉｃｕｍ（Ｂｏｉｓｓ．）ＭＫ（ＡＡ）、ＡｅｇｉｌｏｐｓｓｐｅｌｔｏｉｄｅｓＴａｕｓｃｈ．和Ａｅ．ｔａｕｓｃｈｉｉ（Ｃｏｓｓ．（ＤＤ）的核糖体ＲＮＡ基因ＩＴＳ区进行了ＰＣＲ扩增和克隆,并测定了ＩＴＳ１和ＩＴＳ２的ＤＮＡ序列,讨论和纠正了前人     

从线粒体细胞色素b探讨长臀？属三个种分类与进化的关系

本研究测定了长臂Ｂａ属（Ｍｙｓｔａｃｏｌｅｕｃｕｓ Ｇｕｅｎｔｈｅｒ）中的３个种：月斑长臂Ｂａ（Ｍ．ｃｈｉｌｏｐｔｅｒｕｓ Ｆｏｗｌｅｒ）、长臂Ｂａ〔Ｍ．ｍａｒｇｉｎａｔｕｓ（Ｃｕｖｒｉｅｒ ｅｔ Ｖａｌｅｎｃｉｅｎｎｓｅ）〕和细尾长臂Ｂａ（Ｍ．ｌｅｐｔｕｒｕｓ Ｈｕａｎｇ）共２２个个体的线粒体细胞色素ｂ部分基因片段,其序列为４０８ｂｐ,并选用Ｐａｎｇ Ｐｉ（Ｒｈｏｄｅｕｓ ｓｉｎｅｎｓｉｓ Ｃｕ     

土壤微生物生物量周转的估算

土壤微生物生物量周转的估算高云超,朱文珊,陈文新（北京农业大学生物学院,１０００９４）ＥｓｔｉｍａｔｉｏｎｆｏｒＢｉｏｍａｓｓａｎｄＴｕｒｎｏｖｅｒｏｆＳｏｉｌＭｉｃｒｏｏｒｇａｎｉｓｍｓ￥ＧａｏＹｕｎｃｈａｏ;ＺｈｕＷｅｎｓｈａｎ;ＣｈｅｎＷｅｎｘｉｎ（ＣｏｌｌｅｇｅｏｆＢｉｏｌｏｇｉｃａｌＳｃｉｅｎｃｅｓ,ＢｅｉｊｉｎｇＡｇｒｉｃｕｌｔｕｒａｌＵｎｉｖｅｒｓｉｔｙ,Ｂｅｉｊｉｎｇ１０００９４）．ＣｈｉｎｅｓｅＪｏｕｒ－ｎａｌｏｆＥｃｏｌｏｇｙ,１９９３,１２（６）：６－１０。Ｔｏｏｂｔａｉｎｓｏｍｅｉｎｆｏｒｍａｔｉｏｎａｂｏｕｔｔｒａｎｓｆｏｒｍａｔｉｏｎｏｆｍｉｎｅｒａｌｎｕｔｒｉｅｎｔｓｂｙｓｏｉｌｍｉｃｒｏｏｒｇａｎｉｓｍｓ,ｗｅｈａｖｅｍｅａｓｕｒｅｄｔｈｅａｍｏｕｎｔａｎｄｔｕｒｎｏｖｅｒｒａｔｅｏｆｓｏｉｌｒｎｉｃｒｏｂｉａｌｂｉｏｍａｓｓｉｎｎｏ－ｔｉｌｌａｇｅ,ｄｉｒｅｃｔｄｒｉｌｌｉｎｇａｎｄｐｌｏｗ－ｉｎｇｓｏｉｌｓ．Ｍｉｃｒｏｂｉａｌｂｉｏｒｎａｓｓｉｎｎｏ－ｔｉｌｌａｇｅｔｏｐｓｏｉｌｉｓ５１．７％ａｎｄ２６．０％ｈｉｇｈｅｒｔｈａｎｔｈｏｓｅｉｎｐｌｏｗｉｎｇａｎｄｄｉｒｅｃ     

我国新担子菌类补遗

在研究甘肃、四川、云南的担子菌类时发现如下４新种：云南地红菇（ＭａｃｏｗａｎｉｔｅｓｙｕｎｎａｎｅｎｓｉｓＺａｎｇ）,属红菇科（Ｒｕｓｕｌａｃｅａｅ）,地红菇属（ＭａｃｏｗａｎｉｔｅｓＫａｌｃｈｂｒ．）系我国新记录;松针锈耳（ＣｒｅｐｉｄｏｔｕｓｐｉｎｉｃｏｌａＺａｎｇ）绣耳科（Ｃｒｅｐｉｄｏｔａｃｅａｅ）;蛇盖条孢牛肝菌（ＢｏｌｅｔｅｌｕｓｓｅｒｐｅｎｔｉｐｉｌｅｕｓＺａｎｇｅｔＹｕａｎ）,属松塔牛肝菌［疣孢牛肝菌科］（Ｓｔｒｏｂｉｌｏｍｙｃｏｔａｃｅａｅ）;喜杉绒盖牛肝菌（ＸｅｒｏｃｏｍｕｓｐｉｃｅｉｃｏｌａＺａｎｇｅｔＹｕａｎ）,属牛肝菌科（Ｂｏｌｅｔａｃｅａｅ）;长柄灰包（ＬｙｃｏｐｅｒｄｏｎｌｏｎｇｉｓｔｉｐｕｍＺａｎｇｅｔＹｕａｎ）,属灰包科（Ｌｙｃｏｐｅｒｄａｃｅａｅ）。     

中国兰科植物新资料

本文报道了２个新种（元阳石豆兰ＢｕｌｂｏｐｈｙｌｌｕｍｙｕａｎｙａｎｇｅｎｓｅＴｓｕｉ,长帽隔距兰ＣｌｅｉｓｏｓｔｏｍａｌｏｎｇｉｏｐｅｒｃｕｌａｔｕｍＴｓｉ）、２个新组合（翼萼卷瓣兰ＢｕｌｂｏｐｈｙｌｌｕｍｒｅｔｕｓｉｕｓｃｕｌｕｍＲｃｈｂ．ｆ．ｖａｒ．ｏｒｅｏｇｅｎｅｓ（Ｗ．Ｗ．Ｓｍｉｔｈ）Ｔｓｉ,角萼卷瓣兰Ｂ．ｒｅｔｕｓｉｕｓｃｕｌｕｍＲｃｈｂ．ｆ．ｖａｒ．ｔｉｇｒｉｄｕｍ（Ｈａｎｃｅ）Ｔｓｉ）和１个新命名（细茎毛兰ＥｒｉａｔｅｎｕｉｃａｕｌｉｓＳ．Ｃ．ＣｈｅｎｅｔＴｓｉ）。     

峨眉山自然保护区的虫草及其它昆虫病原真菌I.

采自四川省峨眉山自然保护区的虫草及其相关昆虫病原真菌,其中除有常见的蛹虫草Ｃｏｒｄｙｃｅｐｓｍｉｌｉｔａｒｉｓ（Ｖｕｉｌｌ）,Ｆｒ粉被虫草（ＣｏｒｄｙｃｅｐｓｐｒｕｉｎｏｓａＰｅｔｃｈ）蝉拟青霉Ｐａｅｃｉｌｏｍｙｃｅｓｃｉｃａｄａｅ（Ｍｉｑｕｅｌ）Ｓａｍｓｏｎ,球孢白僵菌Ｂｅａｕｖｅｒｉａｂａｓｓｉａｎａ（Ｂａｌｓ．）Ｖｕｉｌｌ等昆虫病原真菌外,将主要描述峨眉虫草新种（Ｃｏｒｄｙｃｅｐｓｅｍｅｉｅ     

柞蚕林生物生产力和干物质转化研究

柞蚕林生物生产力和干物质转化研究温达志,杨思河（中国科学院华南植物研究所,广州５１０６５０）（中国科学院沈阳应用生态研究所,１１００１５）姜波（辽宁省蚕业科学研究所,凤城１１８１０１）ＢｉｏｐｒｏｄｕｃｔｉｖｉｔｙａｎｄＤｒｙＭａｔｔｅｒＴｒａｎｓｆｅｒｏｆＴｕｓｓａｈ－ＦｅｅｄｉｎｇＯａｋＦｏｒｅｓｔ￥ＷｅｎＤａｚｈｉ（ＳｏｕｔｈＣｈｉｎａＩｎｓｔｉ－ｔｕｔｅｏｆＢｏｔａｎｙ,ＡｃａｄｅｍｉａＳｉｎｉｃａ,Ｇｕａｎｇｚｈｏｕ５１０６５０）,ＹａｎｇＳｉｈｅ（ＩｎｓｔｉｔｕｔｅｏｆＡｐｐｌｉｅｄＥｃｏｌｏｇｙ,Ａ－ｃａｄｅｍｉａＳｉｎｉｃａ,Ｓｈｅｎｙａｎｇ１１００１５）,ＪｉａｎｇＢｏ（ＩｎｓｔｉｔｕｔｅｏｆＳｅｒｉｃｕｌｔｕｒａｌＳｃｉｅｎｃｅ,Ｆｅｎｇｃｈｅｎｇ,ＬｉａｏｎｉｎｇＰｒｏｖｉｎｃｅ１１３１００）．ＣｈｉｎｅｓｅＪｏｕｒｎａｌｏｆＥｃｏｌｏｇｙ,１９９３,１２（１）：５－１０．ＴｈｅｐｒｅｓｅｎｔｓｔｕｄｙｄｅａｌｓｗｉｔｈｔｈｅｂｉｏｐｒｏｄｕｃｔｉｖｉｔｙａｎｄｄｒｙｍａｔｔｅｒｔｒａｎｓｆｅｒｏｆＣｈｉｎｅｓｅＴｕｓｓａｈ－ｆｅｅｄｉｎｇｏａｋｆｏｒｅｓｔｉｎｈｉｌｌｙａｒｅａｏｆｅ     

Predator and Prey Models with Flexible Individual Behavior and Imperfect Information

To begin identifying what behavioral details might be needed to characterize community dynamics and stability, we examined the effect of prey behavioral responses to predation risk on community dynamics and stability. We considered the case of prey altering their foraging effort to trade off energy gain and predation risk. We used state-dependent dynamic optimization to calculate the optimal trade-off for four models of prey behaviorally responding to predation risk. We consider a fixed behavior model in which prey use constant levels of foraging effort and three flexible behavior models in which prey change their foraging effort according to their physiological state and their perceived level of predation risk. Flexible behavior was destabilizing at the community level as evidenced by higher predator-prey oscillations and lower community persistence times. The mechanisms by which prey estimated predation risk also affected community stability. We found that community dynamics resulting from prey with flexible behavior and fixed perception of risk approximated community dynamics resulting from prey with flexible behavior and perfect information about predation risk, however neither approximated the community dynamics resulting from prey with flexible behavior and flexible perception of risk. Thus, whether it might be possible to abstract complex behavior with simpler rules when modeling community dynamics depends on the prey's behavioral mechanisms, which are empirically poorly known.     

Under pressure: Short- and long-term response to predation varies in two populations of a live-bearing fish

The non-lethal effects of predation can significantly influence animal behavior and population composition. Research has often centered around prey response to predator exposure in the short term, but fewer studies have highlighted the effects of long-term predator exposures. In addition, studies of responses to predation risk are not always calibrated against the ecological history of predation risk in specific populations. We address these gaps by examining the effects of both long- and short-term predator exposure on the behavior of individuals from populations that have different ecological histories of predation risk. We exposed individuals from high-predation and low-predation populations of the live-bearing freshwater poeciliid, Heterandria formosa, to predators to assess changes in male reproductive behavior toward females. We also assessed longer-term reproductive responses by exposing male and female H. formosa to predators at a random time of day, every day, for 30 days. In the presence of a predator, in the short term, males changed the frequency of their behaviors and females varied in their concentration of cortisol, demonstrating immediate responses to the perceived risk. The magnitude of these changes was larger in the population without a long history of predator exposure. However, we found that males and females did not change their reproductive output when exposed to predators over longer periods of time, suggesting that individuals acclimatize to the level of predation risk they experience. These results also suggest that short-term variation in behavior or stress hormone responses should not be used as proxies for long-term responses or fitness effects. Future work should assess both short-term behavior and long-term responses while simultaneously considering the ecological history of populations.     

The Use and Transfer of Information About Predation Risk in Flocks of Wintering Finches

Several studies in behavior have focused in some way on how groups of prey gather and use information about predation risk. Although asymmetries in information about risk exist among members of real groups, we know little about how such uneven information might affect individual or group antipredator decisions. Hence, we studied the use and transfer of information about the risk of predation in small flocks of wintering birds. House finches (Carpodacus mexicanus; 28 groups of three) were held in large enclosures divided into safe and risky patches. We controlled the information about risk available to each individual by conducting attacks with a model hawk that was visible to only a single (informed) bird. Repeated attacks on a single individual did not reduce the amount of feeding by other birds in that patch, although the time to resume feeding after observing a response to an attack event was somewhat longer than after a no attack event. These results suggest that informed individuals impart some information to naïve (uninformed) birds, but this effect was not strong. In fact, the frequent return of informed individuals to feeders after observing uninformed individuals feed suggests that finches relied more on public information regarding safety than their own personal information in deciding when to feed. Group patch choice appeared to be based on a majority‐rules decision, although an effect of dominance status was apparent. Our results suggest that subordinate flock members may exert a large influence over group decision‐making by acting as spatial ‘anchors’.     

The influence of the circadian rhythm of green frog (Rana clamitans) tadpoles on their antipredator behavior and the strength of the nonlethal effects of predators

Prey trade off predation risk and foraging gain in their activity level. Their response to this trade-off mediates direct and indirect interactions between predators and the community (i.e., nonlethal effects). A prey's activity level may also vary independently because of circadian rhythms. I tested how the antipredator behavior of green frog (Rana clamitans) tadpoles can be influenced by their circadian rhythm (primarily nocturnal feeding) and how the strengths of nonlethal effects vary in turn. Tadpoles exhibited stronger activity reductions when under predation risk during the day (which may result in stronger resource depression). However, when predation risk was high and persistent, tadpoles remained inactive during both day and night. Consequently, the nonlethal effect on tadpoles (growth rate reduction) was more negative at night. Predicting prey behavior and its effects requires identifying how their perceived risk interacts with and is limited by all factors that can influence their response.     

Predation Risk Perception,Food Density and Conspecific Cues Shape Foraging Decisions in a Tropical Lizard

When foraging, animals can maximize their fitness if they are able to tailor their foraging decisions to current environmental conditions. When making foraging decisions, individuals need to assess the benefits of foraging while accounting for the potential risks of being captured by a predator. However, whether and how different factors interact to shape these decisions is not yet well understood, especially in individual foragers. Here we present a standardized set of manipulative field experiments in the form of foraging assays in the tropical lizard Anolis cristatellus in Puerto Rico. We presented male lizards with foraging opportunities to test how the presence of conspecifics, predation-risk perception, the abundance of food, and interactions among these factors determines the outcome of foraging decisions. In Experiment 1, anoles foraged faster when food was scarce and other conspecifics were present near the feeding tray, while they took longer to feed when food was abundant and when no conspecifics were present. These results suggest that foraging decisions in anoles are the result of a complex process in which individuals assess predation risk by using information from conspecific individuals while taking into account food abundance. In Experiment 2, a simulated increase in predation risk (i.e., distance to the feeding tray) confirmed the relevance of risk perception by showing that the use of available perches is strongly correlated with the latency to feed. We found Puerto Rican crested anoles integrate instantaneous ecological information about food abundance, conspecific activity and predation risk, and adjust their foraging behavior accordingly.     

Influence of ultraviolet-B radiation on growth,prevalence of deformities,and susceptibility to predation in Cascades frog (<Emphasis Type="Italic">Rana cascadae</Emphasis>) larvae

Ambient levels of ultraviolet-B radiation (UVB) have a variety of detrimental effects on aquatic organisms. These include death and effects on growth, development, physiology, and behavior. Amphibians show all of these effects. However, the effects vary with species, life history stage, and ecological context. Little is known about the implications of the detrimental effects of UVB on ecological dynamics. Our study was designed to test how UVB may affect predator–prey interactions, an important ecological dynamic. Specifically, we tested the effect of UVB on the susceptibility of Cascades frog (Rana cascadae) larvae to predation by rough-skinned newts (Taricha granulosa). We also further examined the sublethal effects of UVB on growth and development in Cascades frog larvae. We found no direct effect of UVB exposure on survival. However, UVB-exposed frog larvae displayed decreased growth and increased prevalence of deformities. UVB also caused increased susceptibility to predation, but there was a significant treatment–block interaction. UVB increased susceptibility to predation in two out of five blocks of Cascades frogs. The other three blocks did not show an effect of UVB on susceptibility to predation. Our study suggests that UVB can alter susceptibility to predation in at least one amphibian species. UVB-induced alteration of predator–prey interactions could potentially lead to changes at the population, community, and ecosystem levels. Handling editor: K. Martens     

Experimental determination of predation intensity in an intertidal predator guild: dominant versus subordinate prey

Theoretical and empirical ecologists have long acknowledged that information about the intensity or strength of the interaction between species is crucial for an understanding of community dynamics. In communities in which predation is an important structuring process, and some predator species are commercially exploited, quantitative estimates of predation by different predator species within a guild are necessary to make even the simplest recommendations about conservation and resource management. Here, we evaluated per capita and population level components of predation intensity of three intertidal predators that feed on monospecific stands of barnacles and mussels at wave exposed sites in the rocky intertidal zone of central Chile. These prey species represent the two most distinctive stages of the mid-intertidal seascape, with mussels being competitively dominant. Our results showed that the commercially exploited gastropod Concholepas concholepas and the sea star Heliaster helianthus have similarly large per capita and population effects on the competitively dominant mussel Perumytilus purpuratus . Their per capita (by average size individual) and population effects on mussels were more than two orders of magnitude larger than those of Acanthocyclus gayi crabs and likely even larger than the effect of other predator species in this system (other crabs, whelks, birds, fish). The overall pattern of predation on barnacles was similar to that on mussels, but some differences occurred in the way different components of predation intensity were distributed across predator species. Despite the roughly similar pattern of population predation intensity between prey species, the expected consequences for the prey population, and hence the rest of the community, were acutely different for mussels and barnacles.     

Resource levels and prey state influence antipredator behavior and the strength of nonconsumptive predator effects

The risk of predation can drive trophic cascades by causing prey to engage in antipredator behavior (e.g. reduced feeding), but these behaviors can be energetically costly for prey. The effects of predation risk on prey (nonconsumptive effects, NCEs) and emergent indirect effects on basal resources should therefore depend on the ecological context (e.g. resource abundance, prey state) in which prey manage growth/predation risk tradeoffs. Despite an abundance of behavioral research and theory examining state‐dependent responses to risk, there is a lack of empirical data on state‐dependent NCEs and their impact on community‐level processes. We used a rocky intertidal food chain to test model predictions for how resources levels and prey state (age/size) shape the magnitude of NCEs. Risk cues from predatory crabs Carcinus maenas caused juvenile and sub‐adult snails Nucella lapillus to increase their use of refuge habitats and decrease their growth and per capita foraging rates on barnacles Semibalanus balanoides. Increasing resource levels (high barnacle density) and prey state (sub‐adults) enhanced the strength of NCEs. Our results support predictions that NCEs will be stronger in resource‐rich systems that enhance prey state and suggest that the demographic composition of prey populations will influence the role of NCEs in trophic cascades. Contrary to theory, however, we found that resources and prey state had little to no effect on snails in the presence of predation risk. Rather, increases in NCE strength arose because of the strong positive effects of resources and prey state on prey foraging rates in the absence of risk. Hence, a common approach to estimating NCE strength – integrating measurements of prey traits with and without predation risk into a single metric – may mask the underlying mechanisms driving variation in the strength and relative importance of NCEs in ecological communities.     

Indirect measures of reproductive effort in a resource-defense polygynous ungulate: territorial defense by male guanacos

Trade-offs between reproductive effort and activities that are likely to enhance survival have been studied extensively in harem defense ungulates. However, among resource defense systems, ecological determinants of the variation in male reproductive effort are less understood. The aim of this study was to assess the extent of the effort devoted to territorial defense by male guanacos and how this is affected by predation risk. Time allocation to different activities and displays of aggressive behavior were compared between territorial and bachelor male guanacos within two populations with contrasting levels of predation risk. Territorial males devoted almost twice the time than bachelors to vigilance and moving, at the expense of foraging time. Aggressive interactions were more frequent and severe for territorial males than for bachelors, based on observation. These differences were larger during the reproductive season but remained statistically significant after this period, highlighting the extended effort towards territorial defense beyond the peak of reproductive activity. In contrast to previous observations on females of the same populations, there was no effect of predation risk level or group size on male time allocation, suggesting that under the ecological conditions of the study, intra-sexual competition entails a stronger influence on male individual behavior than predation risk level.     

Relative significance of direct and indirect effects of predation by planktivorous fish on zooplankton

One of the most obvious features of tropical lakes and reservoirs is the small body size of their zooplankton taxa. It is believed that this is the result of high and persistent predation by abundant planktivorous fish, which select large-bodied zooplankton prey thus making them more vulnerable to extinction in tropical as compared to temperate habitats. Do these extinctions result directly from fish predation? Could the high predation-induced mortality alone be responsible for an extermination of the population from a habitat? Or could indirect effects of predation be responsible? Some important indirect effects can be seen at the demographic level; these include reduced reproduction in the population resulting from higher vulnerability of ovigerous females to predation by visually oriented planktivores. Other important indirect effects can be observed at the individual level; these include shifts in behavior (from foraging to predator avoidance) and adjustments in physiology (from high to low feeding rate) in those planktonic animals which detect danger from their predators by sensing either the ‘predator odor’ or an ‘alarm substance’ originating from injured conspecific prey. Although a zooplankton species density may mostly result from the brutal force of direct predator impact on the population (mortality), it is more likely that its distribution in time and space could be attributed to a combination of indirect effects of predation on individual behavior and physiology. An example of periodicity in density and depth distribution patterns of Cahora Bassa zooplankton species and their periodic exterminations seems to confirm the role of indirect effects of predation by planktivorous fish.