Food Webs最新文献

Spore dispersal by insects (entomochory) is a crucial relationship for phalloid fungi, as mycophagous insects carry large amounts of spores and assist stinkhorns in the colonization of new sites. Phallus indusiatus s.l. is a widely distributed fungal species (Basidiomycota), which recruits generalist mycophagous insects as dispersal agents for their spores. Given the lack of knowledge about the natural history of this relationship, it is assumed that its spores are mostly dispersed by insect feces. This study was conducted in a fragment of Amazon forest in Pará, Brazil, and we (i) identified the insects that visited P. indusiatus s.l., (ii) observed the behavior of the insects during this interaction, and (iii) counted the spores carried both on the body surface and in the stomach of the visiting insects. A total of 333 insects associated with six P. indusiatus s.l. basidiomes were recorded. Stingless bees devoted the most time to foraging and were the insects that carried the largest amount of spores, >83 million spores on the body surface and >60 million in the stomach. Wasps presented low abundance, with five minutes dedicated to foraging, carrying just over 7 million spores on the body surface and >2 million in the stomach. The beetles, although possibly sheltering in the basidiomes before the total maturation of P. indusiatus s.l., were the insects with less carried spores, 189,000 spores on the body surface and about 39,000 spores in the stomach. However, they were the most abundant insects among visitors, surpassing the 100 individuals in a single basidiome. Stinkhorns are very valuable resources for forest insects and these fungi take advantage of this interaction to disperse their spores via feces, but mainly by the body surface of visitors.

Salmoniformes are valuable commercial fish that are high in physiologically important omega-3 long-chain polyunsaturated fatty acids (LC-PUFAs), namely eicosapentaenoic (EPA; 20:5n-3) and docosahexaenoic (DHA; 22:6n-3) ones. The content of EPA and DHA and, as a result, the quality of fish for consumers depend on the fish diet. We studied the fatty acid (FA) content and composition of grayling, Thymallus baicalensis, inhabiting six rivers, which differed in food supply for fish. The diet of fish was studied using fatty acid markers in adipose tissue and stomach content. In two rivers, grayling's diet was of aquatic origin, while in four rivers, terrestrial invertebrates constituted a high proportion of the fish diet. The study was conducted to test the following question: How do diets with varying amounts of terrestrial-based food influence the content of EPA and DHA, as well as the fatty acid composition, in various tissues of grayling? Grayling inhabiting shaded rivers had lower nutritional value as a source of LC-PUFAs for consumers compared to those in unshaded rivers. This was reflected in the diets of grayling in shaded rivers, which included more prey relying on terrestrial sources of FAs compared to unshaded rivers, where dietary items relied on autochthonous production. Furthermore, these different diets greatly affected the content of EPA and DHA in muscle and adipose tissue but demonstrated a less significant impact on PUFA content in the brain. These findings are of interest because they suggest that the nutritional value of grayling tissues, consumed by predators, including humans, depends on source material within a river and adjacent terrestrial habitat.

Functional diversity is the heterogeneity in the functional roles of organisms in an ecosystem. Because the morphological traits of species dictate their functional roles, morphological trait diversity has traditionally been used as a proxy for functional diversity. However, species are embedded in a food web and their functional roles also depend on their network positions therein, therefore we argue that functional diversity can also be viewed from a network perspective. We therefore analysed food webs derived from 92 aquatic ecosystems. For every species in a food web, we measured its network position using several indices. Each of the indices emphasize a specific network characteristic, and we consequently call them “species network traits”. We then subjected these network traits to conventional functional diversity analysis to quantify the network-based functional diversity of an ecosystem. We show that high network-based functional diversity is typical of food webs with large network size, sparse in their organization, highly modular structure, or low network cohesion. We further show that our network-based functional diversity correlates weakly with its conventional morphological trait-based counterpart, and thus it provides an additional view on ecological functioning.

This study presents a rare observation of a predator-prey interaction between a tayra (Eira barbara), a semi-arboreal predator, and a group of spider monkeys (Ateles chamek) in Madre de Dios, Peru. The observed pursuit of an A. chamek mother and infant by the E. barbara for an extended time period highlights the evasive tactics and aggressive responses displayed by the spider monkeys. This study reports the first instance of A. chamek as potential prey for the predator. Previous interactions between E. barbara and other primate species are reviewed, revealing varied behavioral responses, including evasion, mobbing, and intimidation. The findings suggest that predator avoidance measures typical of A. chamek, such as habitat avoidance and vigilance, may be less effective against a predator capable of pursuing them through the canopy. Notably, the observed aggression displayed by the spider monkeys towards E. barbara appears distinct compared to their known responses to other predators. Overall, this observation contributes to our understanding of predator-prey dynamics and the adaptive behavior of primates in the face of predation risks.

Butterfly species are regarded as one of the most important members of the plant-pollinator guild. They mainly feed on nectar, and occasionally they rely on pollen. It was reported that butterfly species collect nectar from a greater array of plants. Emperical studies demonstrate that morphological variables of the butterfly species play an important role in foraging. Four morphological variables and two indices, viz., proboscis length, wing span, body length, and weight, and proboscis index and the wing load index of the butterfly species, were used to check their effect on foraging behavior on two plants, viz., Lantana camara (LCA) and Tridax procumbens (TPR), for the current study. Wing load index emerged as the most sensitive factor for foraging on these two plants. Both plants have the highest rate of visits by the butterfly species, with Lantana camara being more frequently visited than Tridax procumbens (TPR). We can conclude that the information gained from this study may help to conserve and sustain the butterfly community in the wild, and this, in turn, may also help to facilitate conservation strategies for the naturally growing nectaring plant species.

Trophic interactions can be both ephemeral and difficult to document, rendering their sampling often incomplete and context-dependent, which makes construction, analysis, and comparison of food webs challenging. Biological traits are central in determining co-occurrence of species (through dispersal, environmental, and interaction filters), as well as the potential for species interactions (through trait matching). Thereby, supplementing empirical, taxonomy-based information on trophic links with trait-based inference may help us build more realistic and adaptable food webs. Here, we go beyond taxonomy to document (i) how traits (e.g., body size, metabolic category and feeding strategy) contribute to local food web structure, and (ii) how associations of consumer-resource traits are structured. We built a trophic-link based trait-interaction network—or trait web—by combining multivariate approaches and network analysis. We found that consumer-resource associations organize into trait profiles that reflect the general vertical structure of the food web, as well as identify groups of limited sets of highly interacting traits. Finally, we discuss the implications of the findings for generating comprehensive and adaptive food webs.

The Hungarian meadow viper (Vipera ursinii rakosiensis) is an endangered subspecies of Vipera ursinii, which faces high predation pressure, partially due to avian species. To create a systematic method for estimating the measure of predation pressure, we developed a geometric morphometric approach to identify both undamaged and damaged vertebrae of snake species found in Hungarian meadow viper habitats from raptor feeding remains. We used linear discriminant analysis with a reference material of vertebrae from identified snake species as training data. We also tested its efficiency by predicting the identification results of different simulation levels based on vertebra completeness. We practiced this method on vertebrae of unknown species of snakes obtained from nests and pellets of short-toed snake eagles (Circaetus gallicus, n = 9), common buzzards (Buteo buteo, n = 14) and Montagu's harriers (Circus pygargus, n = 3). The identification approach showed high accuracy, even in the case of missing landmarks to some extent. We identified vertebrae remnants of Natrix natrix (n = 172, 83.9%), Coronella austriaca (n = 10, 4.9%) and V. u. rakosiensis (n = 23, 11.2%). Both, the reptile specialist C. gallicus and the generalist B. buteo proved to be preying on V. u. rakosiensis, while samples of C. pygargus did not contain any snake remains despite of previous observations of V. ursinii predations. Our approach is applicable for other studies and taxa as well, therefore can be a practical tool for classification of incomplete vertebrae, which is otherwise hardly identifiable. Furthermore, it could be applied to help estimate predation pressure on endangered snake species.

As the importance of both the high seas and gelatinous zooplankton is continuously revealed, it is important to document basic interactions. Physalia are venomous siphonophores, commonly called ‘Man of War’ or ‘Bluebottles’, that use a gas filled float to sail the high seas. Despite being the most conspicuous member of the neustonic ecosystem (the ecosystem at the open ocean's surface), little is known about its life history nor its ecosystem contributions. Herein, two ant species, Solenopsis cf. geminata and Iridomyrmex cf. anceps, were observed foraging on beached colonies of Physalia cf. utriculus in Guam, Micronesia. Ants explored fresh colonies with untriggered stinging cells, yet only disassembled and transported partially dry or degraded colonies. Observations like this improve the understanding of cross-ecosystem dynamics between the coastal and neustonic ecosystem, island trophic structures, and the contribution of gelatinous zooplankton.

Physiological regulation of internal body composition is critical for the fitness of many organisms. Arthropods are abundant around the world and exhibit incredible diversity, yet little is known about how these groups differ in body composition or the mechanisms behind internal changes in chemistry over time. The goal of this study was to examine the lipid and protein content of several common terrestrial arthropod orders, and to determine if this macronutrient composition changes across the season. Additionally, we describe relationships between arthropod body measurements and lipid, protein, and overall dry mass. Arthropod total length and width strongly correlated with macronutrient masses, while other body measurement relationships varied considerably. As expected, arthropod orders varied significantly in both lipid and protein content. Within-order lipid and protein content also varied significantly across the season. These results demonstrate that the nutritional content of invertebrates may fluctuate over time, likely due to shifts in size, ontogeny, and environmental conditions. Understanding the mechanisms behind these changes will be important for unraveling the evolutionary history of these groups as well as the roles they play in surrounding food web structure.

Kleptoparasitism, the theft of food from another individual, is an important interspecific interaction that can have consequences for animal fitness, predation rates, and species' abundance. Similarly, loss of food to fear effects and interspecific interactions can influence energetic costs and consumption rates. Due to their smaller body size and predominantly solitary nature, cheetahs (Acinonyx jubatus) are particularly prone to negative, direct interactions with competing carnivores, and they frequently lose kills to apex predators. However, trophic interactions with other species may have been underreported in the literature. Here, we document anecdotal interactions between cheetah and baboon (Papio spp.) species, across multiple sites in Africa, where baboon troops chased cheetahs off their kills and, in some cases, fed on the remaining carcasses. Given the widespread distribution, and relatively high densities of baboon species across sub-Saharan Africa, we hypothesise that these interactions are likely to be underrepresented in the literature. Since cheetah already experience high levels of competition with apex predators, particularly in South African fenced reserves where competing carnivores are often stocked at densities approaching, or in some cases exceeding, carrying capacity, additional competition and the loss of prey to baboons could further increase predation rates and have implications for reserve management. Baboons are often defensive around large carnivores. As such, interactions with cheetahs are likely to be motivated primarily as a defensive strategy. We encourage further research into food loss, kleptoparasitic behaviour and other competitive interactions between cheetah and Papio species.