Feeding preferences and nutritional niche of wild water buffalo (Bubalus arnee) in Koshi Tappu Wildlife Reserve,Nepal

The nutritional characteristics of food resources play an important role in the foraging behavior of animals and can provide information valuable to their conservation and management. We examined the nutritional ecology of wild water buffalo (Bubalus arnee; hereafter “buffalo”) in the Koshi Tappu Wildlife Reserve of Nepal during autumn using a multidimensional nutritional niche framework. We identified 54 plant species as being foraged by buffalo. We found that buffalo consumed graminoids and forbs 2–3 times more frequently than browse items. Proximate analyses of the 16 most frequently foraged plants indicated that buffalo diets were highest in carbohydrate (40.41% ± 1.82%) followed by crude protein (10.52% ± 0.93%) and crude fat (1.68% ± 0.23%). The estimated macronutrient balance (i.e., realized nutrient niche) of the buffalo diet (20.5% protein: 72.8% carbohydrate: 6.7% lipid) was not significantly different than the average balance of all analyzed food items based on 95% confidence regions. Our study suggests that buffalo are likely macronutrient specialists, yet may be generalists in the sense that they feed on a wide range of food items to achieve a nutrient balance similar to that available in forage items. However, the four most frequently consumed items tended to be higher in protein energy than less frequently consumed foods, suggesting some preference for higher protein forage relative to relatively abundant carbohydrates. Although limited in scope, our study provides important information on the nutritional ecology of buffalo, which may be useful for the conservation and management of this endangered species.     

Diet and macronutrient niche of Asiatic black bear (Ursus thibetanus) in two regions of Nepal during summer and autumn

Relatively little is known about the nutritional ecology of omnivorous Asiatic black bears (Ursus thibetanus) in Nepal. We characterized the diet of black bears in two seasons (June–July, “summer”; and October–November “autumn”) and two study areas (Dhorpatan Hunting Reserve [DHR]; and Kailash Sacred Landscape [KSL]). We then conducted nutritional analysis of species consumed by black bears in each study area, in combination with nutritional estimates from the literature, to estimate the proportions of macronutrients (i.e., protein [P], lipid [L], and carbohydrate [C]) in the seasonal bear foods and diets, as well as their macronutrient niche breadth. We found that bamboo (Arundinaria spp.) had the highest relative frequency in both study areas and seasons. Ants and termites were found in DHR diets, but not KSL diets. One anthropogenic crop was found in DHR summer diets (Zea mays) and two were found in KSL summer diets (Z. mays; and Kodo millet [Paspalum scrobiculatum]). Other than insects, no animal prey was found in either diet. The proportions of macronutrients in diets (i.e., realized macronutrient niches) were relatively high in carbohydrate for both study areas and seasons: DHR_summer 24.1P:8.7L:67.2C; KSL_summer 16.7P:8.2L:75.1C; DHR_autumn 21.1P:10.5L:68.4C; KSH_autumn 19.0P:11.0L:70.0C. Macronutrient niche breadth was 3.1 × greater in the DHR than KSL during summer, and 4.0 × greater in the autumn, primarily due to the higher proportion of lipid in ants and termites relative to plant foods. Within‐study area differences in niche breadth were greater during summer than autumn; in the KSH the macronutrient breadth was 1.4 × greater in summer, while in the DHR it was 1.1 × greater in summer. Similarity in dietary macronutrient proportions despite differences in foods consumed and niche breadth are suggestive of foraging to reach a preferred macronutrient balance.     

Influence of macronutrient imbalance on native ant foraging and interspecific interactions in the field

1. Ants interact with a diversity of organisms. These interactions, coupled with their abundance, cause ants to have ecologically important effects across multiple trophic levels. 2. Empirical study of ant nutritional ecology has led to the prediction that a macronutrient imbalance will affect ant behaviour and interspecific interactions that underlie these broad‐scale effects. Excess carbohydrate relative to protein is predicted to increase ant aggressiveness, predatory tendency and foraging activity, and to decrease collection of hemipteran honeydew and plant nectar. 3. In field experiments conducted in 2009 and 2010, captive colony fragments of a native ant, Formica podzolica (Hymenoptera: Formicidae), were provided with either simulated prey or carbohydrate solution ad libitum. Foraging behaviours and interactions with flowers, myrmecophilous aphids and aphid natural enemies on wild‐grown plants were documented. 4. Strong effects of macronutrient imbalance on foraging manifested quickly and consistently across colonies; in accordance with predictions, prey‐fed foragers collected both honeydew and floral nectar, whereas carbohydrate‐fed ants ceased collecting these resources. Counter to predictions, carbohydrate‐fed ants dramatically lowered their activity levels and did not prey upon aphids. 5. Ants had no effect on aphid enemies in 2009, when the latter were relatively rare, but decreased their abundance in 2010. Despite this protection, the net effect of ants on aphids was negative (measured only in 2009). Prey‐fed ants demonstrated a strong preference for honeydew over floral nectar, thus demonstrating that a macronutrient imbalance may lead to different interactions with similar resources. 6. This study links ant nutrition and community ecology by demonstrating the rapid, asymmetric and multitrophic consequences of nutritionally mediated behaviour.     

The ‘omnivorous badger dilemma’: towards an integration of nutrition with the dietary niche in wild mammals

相似文献   

Seasonal variation in the phytomass,chemical composition and nutritional value of Azolla filiculoides Lam. along the water courses in the Nile Delta,Egypt

The present study aims to assess phenological behaviour, phytomass production, chemical composition and nutritional value of Azolla filiculoides in the water courses of the Nile Delta, Egypt. The sampling process was carried out seasonally using twenty‐five plots (each of 1 × 1 m) distributed along 15 irrigation canals and 10 drainage canals in the study area. Sprouting of A. filiculoides had its maximum activity during winter, vegetative growth during spring and summer and withering during autumn. Maximum seasonal phytomass (285.2 g DW m^‐2) was found during spring. The annual mean was significantly higher in drainage canals (278.3 g DW m^‐2) than in irrigation canals (144.4 g DW m^‐2). The concentrations of Ca, Mg and Na in A. filiculoides from drainage canals were significantly higher than in those from irrigation canals. Regarding the type of water courses, there were no significant differences in organic contents and nutritive values between the irrigation and drainage canals. The analysis of growth characteristics indicated that A. filiculoides can grow quite well in drainage canals; its macronutrient (N, Ca, Mg, Na and Fe) contents are high enough to allow it to be used as a bio‐fertilizer. On the other hand, A. filiculoides could be considered as a ‘nutrients and heavy metals remover’ especially in drainage canals for wastewater treatment if the plant is harvested during its maximum phytomass. As feed supplement for animals, this plant could be considered as excellent forage because its high levels of carbohydrate, protein, crude fat, total digestible nutrients and the lower crude fiber contents (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Constraints on Sedge Meadow Self‐Restoration in Urban Wetlands

Invasive plants and urban run‐off constrain efforts to restore sedge meadow wetlands. We asked if native graminoids can self‐restore following the removal of Typha × glauca (hybrid cattail), and if not, what limits their recovery? After we harvested Typha and depleted its rhizome starch reserves, Carex spp. expanded vegetatively (approximately 1 m over 2 years) but not by recruiting seedlings. A seedling emergence experiment showed that seed banks were depleted where Typha had eliminated the sedge meadow over a decade ago (based on aerial photo analysis). Carex seedling emergence was 75–90% lower where Carex was absent than where it remained in the plant community, and at least 17 species that were abundant 30 years ago were absent from the seed bank and extant vegetation. By varying hydroperiod, we showed that prolonged flooding prevented emergence of Carex seedlings and that a fluctuating hydroperiod reduced emergence and ultimately killed all Carex seedlings. In contrast, Typha seedlings emerged and survived regardless of hydroperiod. Thus, slow vegetative expansion by Carex, depauperate seed banks, and altered hydroperiods all constrain self‐restoration. To compensate for multiple constraints on self‐restoration, we recommend a long‐term management approach that capitalizes on flooding and the capacity of Carex spp. to regrow vegetatively. We suggest annually harvesting swaths of Typha at the edges of clones, before or during flood events, to allow gradual, vegetative self‐restoration of Carex spp.     

The effects of nutritional imbalance on compensatory feeding for cellulose-mediated dietary dilution in a generalist caterpillar

Abstract. The interactive effects of macronutrient balance [protein (P) : carbohydrate (C) ratio] and dietary dilution by cellulose on nutritional regulation and performance were investigated in the generalist caterpillar Spodoptera littoralis (Boisduval). Caterpillars were reared through the final stadium on one of 20 foods varying factorially in macronutrient content (P + C%: 42, 33.6. 25.2 or 16.8%) and P : C ratio (5 : 1, 2 : 1, 1 : 1, 1 : 2 or 1 : 5). The animals compensate by eating more of diluted foods, but suffer reduced nutrient intake in proportion to the degree of dilution. Increase in food intake with dilution is greater on balanced than imbalanced foods and this is reflected in greater reduction of dry pupal mass with dilution in the latter. Whereas dilution results in a reduction in the amount of whichever macronutrient is in excess in the food, by contrast, the ability to compensate for the deficient macronutrient in the food is unaffected by nutrient imbalance. Excess protein intake due to nutritional imbalance (diets with high P : C ratios) results in a regulatory decrease in the efficiency of retention of ingested nitrogen relative to restricted protein intake on oppositely imbalanced foods (low P : C ratios). By contrast, decreased protein intake due to dietary dilution is associated with a non‐regulatory reduction in the efficiency of retention, irrespective of P : C ratio. Dilution is similarly associated with reduced utilization efficiency of ingested carbohydrate. The ecological implications of these results are discussed.     

Effects of diet quality on performance and nutrient regulation in an omnivorous katydid

1. Omnivores by definition eat both plants and animals. However, little is known about how diet macronutrient content affects omnivore performance, or the extent to which they can regulate macronutrient intake. We assessed these questions using the salt marsh katydid, Conocephalus spartinae Fox (Tettigoniidae). 2. In our first experiment we used artificial diets with different protein–carbohydrate ratios to assess the effects of diet quality on survival, growth, and lipid accumulation. We found that diets with a high protein–carbohydrate ratio negatively affected Conocephalus survival. Among surviving individuals growth was not significantly different across the treatments, but lipid content decreased significantly as the protein–carbohydrate ratio of diets increased. 3. In a second experiment we explored the ability of Conocephalus to regulate their protein–carbohydrate intake. Results revealed that Conocephalus did not feed randomly when presented with two nutritionally complementary foods. A detailed analysis of their protein–carbohydrate intake revealed selection for a protein‐biased diet, but a lack of tight regulate of protein–carbohydrate intake. 4. We discuss how key macronutrients can limit omnivores, and how nutritional flexibility may enable omnivores to persist in nutritionally heterogeneous environments.     

Temperature dependency of predation: Increased killing rates and prey mass consumption by predators with warming

Temperature dependency of consumer–resource interactions is fundamentally important for understanding and predicting the responses of food webs to climate change. Previous studies have shown temperature‐driven shifts in herbivore consumption rates and resource preference, but these effects remain poorly understood for predatory arthropods. Here, we investigate how predator killing rates, prey mass consumption, and macronutrient intake respond to increased temperatures using a laboratory and a field reciprocal transplant experiment. Ectothermic predators, wolf spiders (Pardosa sp.), in the lab experiment, were exposed to increased temperatures and different prey macronutrient content (high lipid/low protein and low lipid/high protein) to assess changes in their killing rates and nutritional demands. Additionally, we investigate prey mass and lipid consumption by spiders under contrasting temperatures, along an elevation gradient. We used a field reciprocal transplant experiment between low (420 masl; 26°C) and high (2,100 masl; 15°C) elevations in the Ecuadorian Andes, using wild populations of two common orb‐weaver spider species (Leucauge sp. and Cyclosa sp.) present along the elevation gradient. We found that killing rates of wolf spiders increased with warmer temperatures but were not significantly affected by prey macronutrient content, although spiders consumed significantly more lipids from lipid‐rich prey. The field reciprocal transplant experiment showed no consistent predator responses to changes in temperature along the elevational gradient. Transplanting Cyclosa sp. spiders to low‐ or high‐elevation sites did not affect their prey mass or lipid consumption rate, whereas Leucauge sp. individuals increased prey mass consumption when transplanted from the high to the low warm elevation. Our findings show that increases in temperature intensify predator killing rates, prey consumption, and lipid intake, but the responses to temperature vary between species, which may be a result of species‐specific differences in their hunting behavior and sensitivity to temperature.     

Dietary generalists and nutritional specialists: Feeding strategies of adult female blue monkeys (Cercopithecus mitis) in the Kakamega Forest,Kenya

Generalist primates eat many food types and shift their diet with changes in food availability. Variation in foods eaten may not, however, match variation in nutrient intake. We examined dietary variation in a generalist‐feeder, the blue monkey (Cercopithecus mitis), to see how dietary food intake related to variation in available food and nutrient intake. We used 371 all‐day focal follows from 24 adult females (three groups) in a wild rainforest population to quantify daily diet over 9 months. We measured food availability using vegetation surveys and phenology monitoring. We analyzed >700 food and fecal samples for macronutrient content. Subjects included 445 food items (species‐specific plant parts and insect morphotypes) in their diet. Variation in fruit consumption (percentage of diet and total kcal) tracked variation in availability, suggesting fruit was a preferred food type. Fruits also constituted the majority of the diet (by calories) and some fruit species were eaten more than expected based on relative availability. In contrast, few species of young leaves were eaten more than expected. Also, subjects ate fewer young leaves (based on calories consumed) when fruit or young leaves were more available, suggesting that young leaves served as fallback foods. Despite the broad range of foods in the diet, group differences in fiber digestibility, and variation that reflected food availability, subjects and groups converged on similar nutrient intakes (grand mean ± SD: 637.1 ± 104.7 kcal overall energy intake, 293.3 ± 46.9 kcal nonstructural carbohydrate, 147.8 ± 72.4 kcal lipid, 107.8 ± 12.9 kcal available protein, and 88.1 ± 17.5 kcal structural carbohydrate; N = 24 subjects). Thus, blue monkeys appear to be food composition generalists and nutrient intake specialists, using flexible feeding strategies to regulate nutrient intake. Findings highlight the importance of simultaneously examining dietary composition at both levels of foods and nutrients to understand primate feeding ecology.     

Macronutrient balancing in free‐ranging populations of moose

At northern latitudes, large spatial and temporal variation in the nutritional composition of available foods poses challenges to wild herbivores trying to satisfy their nutrient requirements. Studies conducted in mostly captive settings have shown that animals from a variety of taxonomic groups deal with this challenge by adjusting the amounts and proportions of available food combinations to achieve a target nutrient balance. In this study, we used proportions‐based nutritional geometry to analyze the nutritional composition of rumen samples collected in winter from 481 moose (Alces alces) in southern Sweden and examine whether free‐ranging moose show comparable patterns of nutrient balancing. Our main hypothesis was that wild moose actively regulate their rumen nutrient composition to offset ecologically imposed variation in the nutritional composition of available foods. To test this, we assessed the macronutritional composition (protein, carbohydrates, and lipids) of rumen contents and commonly eaten foods, including supplementary feed, across populations with contrasting winter diets, spanning an area of approximately 10,000 km². Our results suggest that moose balanced the macronutrient composition of their rumen, with the rumen contents having consistently similar proportional relationship between protein and nonstructural carbohydrates, despite differences in available (and eaten) foods. Furthermore, we found that rumen macronutrient balance was tightly related to ingested levels of dietary fiber (cellulose and hemicellulose), such that the greater the fiber content, the less protein was present in the rumen compared with nonstructural carbohydrates. Our results also suggest that moose benefit from access to a greater variety of trees, shrubs, herbs, and grasses, which provides them with a larger nutritional space to maneuver within. Our findings provide novel theoretical insights into a model species for ungulate nutritional ecology, while also generating data of direct relevance to wildlife and forest management, such as silvicultural or supplementary feeding practices.     

Carbohydrate scarcity increases foraging activities and aggressiveness in the ant Prolasius advenus (Hymenoptera: Formicidae)

1. Behavioural responses to varying macronutrient availability are increasingly studied in highly invasive ant species to better understand their ecological success. However, such work is lacking in relation to native ant species confronted with biological invaders. 2. Here the link between diet and behaviour was examined in Prolasius advenus, a native ant from New Zealand facing intense competition for food with invasive insects, including social wasps. A long‐term laboratory experiment was conducted to assess the impact of protein and carbohydrate restriction on several behavioural parameters. 3. Ants shifted their food‐collecting activity towards the least available macronutrient in both protein‐limited and carbohydrate‐limited colonies. But when lacking carbohydrate, they also strongly increased their efforts to discover resources. After 10 weeks, the proportion of the colony patrolling outside of the nest was eight times higher than at the initiation of the experiment. This high patrolling activity was then maintained for several weeks and resulted in a higher efficiency to explore a novel territory. Moreover, ants fed a carbohydrate‐limited diet engaged in longer aggressive acts towards conspecifics. 4. These behavioural responses to carbohydrate scarcity may, in part, enhance the ability of P. advenus to resist a competing invader under natural conditions. While much of the previous research has linked diet and behavioural dominance in invasive ants, the present study shows that conducting similar investigations in the native species to which they are confronted may shed light on the mechanisms behind biotic resistance and the ability of some native species to coexist with highly abundant invaders.     

Phylogeny and Evolution in Cariceae (Cyperaceae): Current Knowledge and Future Directions

The goal of this study was to review the impact of DNA sequence analyses on our understanding of Cariceae phylogeny, classification and evolution. To explore character evolution, 105 taxa from four different studies were included in an nrDNA ITS + ETS 1f analysis of all recognized genera (Carex, Cymophyllus, Kobresia, Schoenoxiphium, Uncinia) and Carex subgenera (Carex, Psyllophora, Vignea, Vigneastra). As in previous analyses, four major Cariceae clades were recovered: (1) a “Core Carex Clade” (subg. Carex, Vigneastra, Psyllophora p.p); (2) A “Vignea Clade” (subg. Vignea, Psyllophora p.p.); (3) a “Schoenoxiphium Clade” (Schoenoxiphium, subg. Psyllophora p.p.), and (4) a “Core Unispicate Clade” (Uncinia, Kobresia, subg. Psyllophora p.p.). All studies provide strong support (86–100% BS) for the Core Carex and Vignea Clades, but only weak to moderate support (<50%–78% BS) for the Core Unispicate and Schoenoxiphium Clades. The relationships of these groups are unresolved. Studies suggest that Carex is either paraphyletic with respect to all Cariceae genera or to all genera except Schoenoxiphium. Kobresia is a grade, but Uncinia and possibly Schoenoxiphium are monophyletic. The monotypic Cymophyllus is indistinct from Carex subg. Psyllophora species. Character analyses indicate that inflorescence proliferation and reduction have occurred in all major clades, and that the Cariceae’s unisexual flowers have evolved from perfect flowers. The ancestor to Cariceae possessed a multispicate inflorescence with cladoprophylls and female spikelets with tristigmatic gynoecia and closed utricles. This morphology is most similar to extant Carex subg. Carex species, which contradicts the nearly unanimous assumption that the highly compound inflorescences of Schoenoxiphium are primitive. Since taxonomic sampling and statistical support for phylogenies have generally been poor, we advocate the temporary maintenance of the four traditional Carex subgenera with androgynous unispicate species placed within subg. Psyllophora and dioecious and gynaecandrous unispicate species distributed amongst subgenera Carex and Vignea. A collective effort focused on developing new nuclear markers, on increasing taxonomic and geographic sampling, and on studying development within the context of phylogeny, is needed to develop a phylogenetic classification of Cariceae.     

Three hundred and fifty generations of extreme food specialisation: testing predictions of nutritional ecology

We used a strain of diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae), that had been reared for approximately 350 generations in a precisely characterised environment to test hypotheses regarding the influence of nutritional heterogeneity on the evolution of nutrient regulatory responses. Caterpillars were maintained with ad libitum access to a diet that emulated that of an extreme nutritional specialist, comprising a homogeneous food of fixed nutrient composition. We measured performance (survival, development rate, and pupal mass), as well as the protein and carbohydrate intake of individual caterpillars confined to one of a range of single foods differing in their protein, carbohydrate, and water content. In a separate experiment, we measured the amount and balance of protein and carbohydrate self-selected by caterpillars presented with nutritionally complementary foods. Results showed a close fit with three of four predictions about the nutritional responses of 'nutrient specialist' feeders: (1) survival, development rate, and pupal mass were highest for animals given diets with the protein:carbohydrate composition of the ancestral culture diet, and dropped off sharply with higher and lower protein:carbohydrate balance, (2) caterpillars coped poorly with dietary dilution by water, irrespective of the macronutrient balance, and (3) the self-selected intake point corresponded with the macronutrient balance that gave peak performance (i.e., that of the ancestral culture diet). The fourth prediction, that caterpillars would be disinclined to over-ingest nutrients on imbalanced diets, was at best weakly met. We hypothesise that the evolution and maintenance of the specialist strategy might, paradoxically, require some degree of environmental heterogeneity.     

A regional approach to plant DNA barcoding provides high species resolution of sedges (Carex and Kobresia, Cyperaceae) in the Canadian Arctic Archipelago

Previous research on barcoding sedges (Carex) suggested that basic searches within a global barcoding database would probably not resolve more than 60% of the world’s some 2000 species. In this study, we take an alternative approach and explore the performance of plant DNA barcoding in the Carex lineage from an explicitly regional perspective. We characterize the utility of a subset of the proposed protein-coding and noncoding plastid barcoding regions (matK, rpoB, rpoC1, rbcL, atpF-atpH, psbK-psbI) for distinguishing species of Carex and Kobresia in the Canadian Arctic Archipelago, a clearly defined eco-geographical region representing 1% of the Earth’s landmass. Our results show that matK resolves the greatest number of species of any single-locus (95%), and when combined in a two-locus barcode, it provides 100% species resolution in all but one combination (matK + atpFH) during unweighted pair-group method with arithmetic mean averages (UPGMA) analyses. Noncoding regions were equally or more variable than matK, but as single markers they resolve substantially fewer taxa than matK alone. When difficulties with sequencing and alignment due to microstructural variation in noncoding regions are also considered, our results support other studies in suggesting that protein-coding regions are more practical as barcoding markers. Plastid DNA barcodes are an effective identification tool for species of Carex and Kobresia in the Canadian Arctic Archipelago, a region where the number of co-existing closely related species is limited. We suggest that if a regional approach to plant DNA barcoding was applied on a global scale, it could provide a solution to the generally poor species resolution seen in previous barcoding studies.     

Dietary selection and nutritional regulation in a common mixed‐feeding insect herbivore

The geometric framework provides a way for understanding the multi‐dimensional nutritional relationships between consumers and their food. We use this approach to further our understanding of the feeding and nutritional ecology of a ubiquitous mixed‐feeding insect herbivore that consumes a variety of host plants spanning a wide range of nutritional composition. Our overall objective was to examine feeding decisions, resulting performance, and post‐ingestive consequences in a common mixed‐feeding insect herbivore, Melanoplus bivittatus (Say) (Orthoptera: Acrididae), when presented with paired diets differing in protein:carbohydrate (p:c) ratio. Intake p:c of M. bivittatus differed among all but two treatments and in many cases was farther than expected from the previously identified p:c intake target for this species. Despite this variability in intake of protein and carbohydrate, we found few effects of the diet treatments on performance or post‐ingestive processing. However, our results suggest that when feeding on high‐quality diets, nutrients consumed in excess may be stored rather than excreted.     

鄱阳湖越冬雁类食源植被适宜取食时间窗口

雁类是长江中下游越冬水鸟的优势种群,以苔草(Carex spp)等湿生植被为主要食物来源。作为长江中下游仅存的通江湖泊之一,鄱阳湖显著受到水文波动的影响,湿地植被的生长发育与洲滩淹没和出露时间密切相关。雁类对食物资源具有高度的选择性,建立雁类取食植被的特征和苔草生长过程之间的关系,是刻画适宜栖息地时空分布范围,开展雁类及其食物资源保育的关键。选择鄱阳湖典型子湖泊常湖池作为研究区,对苔草春季生长期开展了原位观测试验,对4个高程梯度的苔草株高和生物量等关键生长因子进行了12次野外监测和采样。同时,结合遥感影像、气温数据及实地观测记录,确定了4个高程梯度洲滩的出露时间和苔草有效生长时间。在此基础上,建立了基于Logistic方程的苔草株高和生物量的生长过程曲线。并根据实地观测的雁类觅食苔草的特征,反推得到雁类适宜取食苔草的时间窗口。结果表明:苔草株高与地上生物量显著正相关,水文条件和气温是影响苔草生长的关键因素,而退水时间的推迟,会导致生长期缩短和低温限制下的有效生长时间减少,影响雁类食物资源的分布。苔草在秋季生长期出露达到12—28 d,而在春季生长期出露达到83—182 d时适宜雁类取食。研究提出了确定越冬雁类苔草适宜取食时间窗口的方法,证实洲滩退水时间推迟超过20 d,苔草生长节律将难以匹配雁类数量峰值期觅食的需要。本研究对鄱阳湖湿地水文调控和湿地资源管理具有重要意义。     

Digestion and metabolism of a natural foliar diet (Eucalyptus punctata) by an arboreal marsupial, the koala (Phascolarctos cinereus)

Summary Digestion and energy metabolism in an arboreal marsupial, the koalaPhascolarctos cinereus, fed mature foliage from a common food tree, the grey gumEucalyptus punctata, were investigated. Six feeding (balance) experiments, at various times of year, and one slaughter experiment were performed and average daily oxygen consumption was measured.The average apparent digestibilities of dietary constituents were: dry matter 54%; total cell-contents 69%; available carbohydrate 92%; crude lipid 43%; total nitrogen 45%; total phenolics 91%; total cell walls 25%; hemicellulose 24%; acid-detergent fibre 25%; cellulose 31%; lignin 19%.Average digestible and metabolizable energy intakes were 0.50 and 0.43 MJ kg^–0.75 d^–1 respectively of which only 0.28 MJ kg^–0.75 d^–1 was expended in oxidative metabolism. The digestible energy intake required for maintenance was estimated to be 0.33 MJ kg^–0.75 d^–1, which is lower than that of eutherian and of other marsupial herbivores. The principal sources of metabolizable energy were non-structural carbohydrate and lipid.It is postulated that the ability of koalas to utilizeEucalyptus foliage as a sole source of nutrients is facilitated by their low requirement for energy and their ability to maximize intake of non cell-wall constituents.E. punctata foliage has a high digestible energy content compared with the foliage of many other trees and this may be a factor in its selection by koalas.Abbreviations DMI dry matter intake - DMD dry matter digestibility - DE digestible energy - ME metabolizable energy     

Acclimation of the photosynthetic apparatus and alterations in sugar metabolism in response to inoculation with endophytic fungi

The role of an endophytic Zygomycete Mucor sp. in growth promotion and adaptation of the photosynthetic apparatus to increased energy demands of its hosts Arabidopsis arenosa and Arabidopsis thaliana was evaluated. Inoculation with the fungus improved the water use efficiency of the plants and allowed for them to utilize incident light for photochemistry more effectively by upregulating the expression of several photosystem I‐ and II‐related genes and their respective proteins, proteins involved in light harvesting in PSII and PSI and carbon assimilation. This effect was independent of the ability of the plants to acquire nutrients from the soil. We hypothesize that the accelerated growth of the symbiotic plants resulted from an increase in their demand for carbohydrates and carbohydrate turnover (sink strength) that triggered a simultaneous upregulation of carbon assimilation. Arabidopsis plants inoculated with Mucor sp. exhibited upregulated expression in several genes encoding proteins involved in carbohydrate catabolism, sugar transport, and smaller starch grains that indicate a significant upregulation of carbohydrate metabolism.     

Early changes in species composition of upland sown grassland under extensive grazing management

Abstract. Due to economic pressures and policy changes Lolium perenne‐Trifolium repens sown swards in upland UK sheep systems are likely to become less intensively managed. We present results from the first 5 yr of a long‐term experiment studying vegetation change under more extensive grazing management at three sites. One treatment was representative of current, intensive management and 5 were unfertilized with different intensities of seasonal grazing. The species composition of unfertilized, ungrazed swards changed dramatically within 2 yr and the sown species had virtually disappeared by year 5. Ranunculus repens, Poa trivialis, Agrostis gigantea, Juncus spp. and Carex spp. became dominant at the wettest site. Grasses were dominant at the other sites. In contrast, the sown species were retained in the unfertilized, grazed treatments; there were small shifts in abundance of the species present initially and few additions or losses of species. Some colonizing species were present in the seed bank whereas others with a transient seed bank appeared to have invaded from neighbouring vegetation. Implications of these results for compensation schemes to reduce animal output and increase biodiversity are discussed.