Predation of the sea urchin Heliocidaris erythrogramma by rock lobsters (Jasus edwardsii) in no-take marine reserves

The formation of sea urchin ‘barrens’ on shallow temperate rocky reefs is well documented. However there has been much conjecture about the underlying mechanisms leading to sea urchin barrens, and relatively little experimentation to test these ideas critically. We conducted a series of manipulative experiments to determine whether predation mortality is an important mechanism structuring populations of the sea urchin Heliocidaris erythrogramma in Tasmania. Tethered juvenile and adult sea urchins experienced much higher rates of mortality inside no-take marine reserves where sea urchin predators were abundant compared to adjacent fished areas where predators were fewer. Mortality of tagged (but not tethered) sea urchins was also notably higher in marine reserves than in adjacent areas open to fishing. When a range of sizes of sea urchins was exposed to three sizes of rock lobsters in a caging experiment, juvenile sea urchins were eaten more frequently than larger sea urchins by all sizes of rock lobster, but only the largest rock lobsters (> 120 mm CL) were able to consume large adult sea urchins. Tagging (but not tethering) juvenile and adult sea urchins in two separate marine reserves indicated that adult sea urchins experience higher predation mortality than juveniles, probably because juveniles can shelter in cryptic microhabitat more effectively. In a field experiment in which exposure of sea urchins to rock lobster (Jasus edwardsii) and demersal reef fish predators was manipulated, rock lobsters were shown to be more important than fish as predators of adult sea urchins in a marine reserve. We conclude that predators, and particularly rock lobsters, exert significant predation mortality on H. erythrogramma in Tasmanian marine reserves, and that adult sea urchins are more vulnerable than smaller cryptic individuals. Fishing of rock lobsters is likely to reduce an important component of mortality in H. erythrogramma populations.     

The effects of starvation on development and reproductive potential of apterous virginoparae of vetch aphid, Megoura viciae

Apterous virginoparae of Megoura viciae Buckton starved during the fourth instar lost weight but nevertheless completed their development, showing that growth and development could proceed independently. Their weight at the end of starvation was a function of initial weight. Aphids used considerable amounts of lipid during starvation, and if allowed to feed on becoming adult showed a delayed onset to reproduction. Starvation in the fourth instar arrested embryogenesis, and in small aphids resulted in degeneration of gonadal and somatic tissues.

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Résumé Des virginipares de M. viciae Buckton, privées de nourriture à partir de la mue au quatrième stade, achèvent leur développement et muent en adulte en perdant du poids; elles montrent que croissance et développement peuvent être indépendants. Le jeûne pendant le quatrième stade provoque en moyenne la perte de 84% des réserves lipidiques. Le poids à la mue imaginale dépend significativement du poids lors de la mue du quatrième stade: de petits pucerons achèvent leur développement plus lentement que les gros. Le jeûne pendant le 4ème stade interrompt l'ovulation et le développement des gonades; lorsque les adultes peuvent se réalimenter après ce jeûne, la période précédant la ponte est plus longue. L'examen histologique montre que les pucerons les plus petits subissent une régression somatique et gonadale plus importante que les plus lourds: la dégenérescence des gonades apparaît chez les petits pucerons après le jeûne au 4ème stade, tandis que les plus gros voient leur potentiel reproductif réduit par un arrêt de l'embryogenèse.

     

Management of fat reserves and food caches in tufted titmice (Parus bicolor) in relation to unpredictable food supply

In the temperate zone, permanent-resident birds and mammalsthat do not hibernate must survive harsh winter conditions oflow ambient temperature, long nights, and reduced food levels.To understand the energy management strategy of food-hoardingbirds, it has been hypothesized that such birds respond to increasedstarvation risk by increasing the number of their hoards ratherthan by increasing their fat reserves and that they cache earlyin the day and retrieve their caches later to achieve fat reservesnecessary to survive the night We tested these hypotheses byobserving the responses in captivity of a caching bird, thetufted titmouse (Parus bicolor), to the combined influencesof reduced predictability of food and naturally occurring ambienttemperature and photoperiod. When the food supply was unpredictable,birds significantly increased both internal fat reserves atdusk and external food caches. Initially leaner birds tendedto increase their fat reserves to a greater extent and initiallyfatter birds tended to cache more food and to fly significantlyless. Half the birds also increased their dawn and mean dailybody mass. All birds tended to forage, gain body mass, and cachefood at significantly lower rates in the morning and at significantlyhigher rates in the evening. Cache retrieval showed the oppositetrend, with birds retrieving most of their caches in the morning.Our results do not support the hypothesis that caching birdsincrease caching rate but not body mass under an unpredictablefood regime. Instead fat reserves and food caches are both importantcomplementary sources of energy in food-hoarding birds. Energymanagement by wintering birds occurs in response to a numberof biotic and abiotic factors acting simultaneously; thus futuremodels must incorporate independent variables in addition tothe state of the food supply and time of day     

The effect of a day at low irradiance of a maize crop. II. Photosynthesis, transpiration and respiration

The kinetics of daily photosynthesis, transpiration and dark respiration of shoots of maize plants ( Zea mays L.) were studied in a growth chamber. After one or two days of reduced light intensity, the photosynthesis and the transpiration returned immediately to a level higher than expected. Respiration, which was reduced by at least 50%, returned slowly for over 2 days towards the initial level. These results suggest the existence of reserves of assimilation products which are used up while maintaining the growth of the aerial part in spite of the lack of assimilation. The prolonged reduction of the respiration shows that it is not strongly correlated to photosyntheis or to growth but rather to the amount of available reserves of assimilate.     

Impact of game hunting by the Kayapó of south-eastern Amazonia: implications for wildlife conservation in tropical forest indigenous reserves

Indigenous forest reserves represent approximately one fifth of Brazilian Amazonia and pose enormous challenges for sustainable natural resource management by native Amazonians. In collaboration with the Kayapó Indians of A’Ukre of southeastern Amazonia, we obtained a game harvest profile of over 1360 forest vertebrates consumed at this village over a 20-month period, including 743 mammals, 361 forest tortoises and 256 birds from a minimum of 42 game species. This amounted to a total of 13,775 kg of game animals harvested over the entire study (mean = 26.2 kg d⁻¹). We also obtained some 450 km of line transect census data of midsized to large-bodied vertebrates within the core hunting catchment of this village and in an unhunted but otherwise comparable site upriver of A’Ukre. Population density estimates of 16 of the 18 species censused were significantly depressed by hunting by central place foragers within the village catchment, and a number of harvest-sensitive prey species showed clear evidence of local depletion. For the time being, however, we can conclude that hunting was sustainable at the landscape scale largely because source-sink dynamics in the context of low village catchment density is made possible by large surrounding tracts of primary forest that remain unharvested or underharvested.     

Physiological and biological patterns of a highland and a coastal population of the European cherry fruit fly during diapause

Adult emergence of univoltine temperate insect species and its synchronization with specific host phenological stages is mainly regulated by obligatory pupal diapause. Although a few studies have investigated the factors affecting diapause intensity, little attention has been paid to the physiological alterations and metabolic regulation that take place during diapause. Here, we describe differences in diapause between a highland and a coastal Greek population of the European cherry fruit fly Rhagoletis cerasi, a major pest of sweet and sour cherries in many European countries. Pupae of both populations were exposed to the environmental conditions prevailing in the two areas and diapause termination was observed under laboratory conditions. The regulation of energetic metabolites during the long pupae stage was examined under both field and laboratory conditions. Differences in diapause intensity revealed that the two populations have adapted to the local geographical and climatic conditions and have different requirements for low temperatures to terminate diapause. The coastal population undergoes a shorter diapause and adults emerge more rapidly, especially in the highland area. The highland population failed to terminate diapause (<40% adult emergence) in the coastal area. Both populations draw on their major energetic reserves (lipids and protein) similarly during diapause. Nevertheless, regulation of carbohydrate and glycogen reserves seems to vary between the populations: major peaks of these stored nutrients occur on different dates in the two populations, suggesting a differential regulation. Differences in diapause intensity imply a genetic differentiation between the two populations. The importance of our findings in understanding the physiological patterns during obligatory diapause of a univoltine insect species, as well as the practical implications for the development of specific phenological models for the European cherry fruit fly are discussed.     

Harmaline ingestion effect on development,metabolites and midgut of the red flour beetle,Tribolium castaneum

Alkaloids constitute an interesting family of molecules synthesized and accumulated by certain plants and it suggested that they participate in plant defences. In this study, we determined the ingestion effect of the alkaloid, harmaline, on the insect pest Tribolium castaneum Herbst (Coleoptera: Tenebrionidae). When incorporated into the diet at 400, 1000, and 2000 ppm, harmaline provoked larval weight loss, larval mortality and adult emergence inhibition. Spectrophotometric analyses showed that harmaline ingestion caused a significant diminution in the rate of protein, glycogen and lipid. Besides, the activity of the enzyme α-amylase was also significantly reduced in treated larvae. In addition, by using the optical and electron microscopy, we have showed that harmaline ingestion induced a marked cytotoxic effect on the midgut epithelial cells. They exhibited rare microvilli and an extensive disorganization and vacuolisation of the cytoplasm and the nucleus. In conclusion, the results obtained from this study prove and show potent insecticidal effect of Alkaloids such as harmaline on Tribolium castaneum.     

Life histories predict coral community disassembly under multiple stressors

Climate change is reshaping biological communities against a background of existing human pressure. Evaluating the impacts of multiple stressors on community dynamics can be particularly challenging in species‐rich ecosystems, such as coral reefs. Here, we investigate whether life‐history strategies and cotolerance to different stressors can predict community responses to fishing and temperature‐driven bleaching using a 20‐year time series of coral assemblages in Kenya. We found that the initial life‐history composition of coral taxa largely determined the impacts of bleaching and coral loss. Prior to the 1998 bleaching event, coral assemblages within no‐take marine reserves were composed of three distinct life histories – competitive, stress‐tolerant and weedy– and exhibited strong declines following bleaching with limited subsequent recovery. In contrast, fished reefs had lower coral cover, fewer genera and were composed of stress‐tolerant and weedy corals that were less affected by bleaching over the long term. Despite these general patterns, we found limited evidence for cotolerance as coral genera and life histories were variable in their sensitivities to fishing and bleaching. Overall, fishing and bleaching have reduced coral diversity and led to altered coral communities of ‘survivor’ species with stress‐tolerant and weedy life histories. Our findings are consistent with expectations that climate change interacting with existing human pressure will result in the loss of coral diversity and critical reef habitat.     

贵州道地苗药对对参立地环境研究

对贵州道地苗药对对参生长立地环境、气候状况、土壤理化特性及蕴藏量进行研究,研究结果表明：对对参生长在中缓坡地带或较陡山坡上的小块平洼地;岩石较多,岩土比达1：1以上;对对参生长地区气候温和、降雨充沛、阳光充足、热量资源丰富;土壤有机质含量高,有良好的团粒结构;土壤水分含量高;土壤呈弱碱性;土壤养分中氮元素的含量丰富,而速效磷、钾的含量则较少;表明对对参是一种喜阳、喜热、喜湿及喜氮的植物;对对参资源蕴藏量少.     

Designing nature reserves in the face of uncertainty

Conservation reserves are a fundamental tool for managing biodiversity. The so-called SLOSS debate--should we have a Single Large Or Several Small reserves - is central to conservation theory. Population dynamic models suggest that the design that minimizes the risk of extinction of a species is case-specific, with the optimal number of reserves ranging between one and very many. Uncertainty is pervasive in ecology, but, the previous analyses of the SLOSS debate have not considered how uncertainty in the model of extinction risk might influence the optimal design. Herein, we show that when uncertainty is considered, the SLOSS problem is simplified and driven more by the aspirations of the manager than the population dynamics of the species. In this case, the optimal solution is to have in the order of twenty or fewer reserves for any species. This result shows counter-intuitively that considering uncertainty actually simplifies rather than complicates decisions about designing nature reserves.