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141.
Cycling index is an important ecological indicator used in ecosystem analysis. The higher the cycling in an ecosystem, the higher the utilization of mass and energy within the system before it is lost due to respiration and other factors. For a stock-flow type ecosystem model at steady state, Finn’s cycling index (FCI) can be computed using simple matrix algebra. However, it is difficult to measure how well this index represents the actual cycling occurring in the system. In this paper, we study cycling in ecological networks using an individual based approach (particle tracking algorithm). This new simulation method provides access to the pathway data of individual particles that flow in the system, therefore one can quantify cycling using this pathway data quite literally. We used particle tracking simulations (PTS) to compute a cycling index using Finn’s idea of flux based cycling. Our simulation based results (using no matrix algebra) agree with Finn’s cycling index, verifying the accuracy of both the PTS, and the original linear algebraic formulation of FCI. 相似文献
142.
Authors of socioecological models propose that food distribution affects female social relationships in that clumped food
resources, such as fruit, result in strong dominance hierarchies and favor coalition formation with female relatives. A number
of Old World monkey species have been used to test predictions of the socioecological models. However, arboreal forest-living
Old World monkeys have been understudied in this regard, and it is legitimate to ask whether predominantly arboreal primates
living in tropical forests exhibit similar or different patterns of behavior. Therefore, the goal of our study was to investigate
female dominance relationships in relation to food in gray-cheeked mangabeys (Lophocebus albigena). Since gray-cheeked mangabeys are largely frugivorous, we predicted that females would have linear dominance hierarchies
and form coalitions. In addition, recent studies suggest that long food site residence time is another important factor in
eliciting competitive interactions. Therefore, we also predicted that when foods had long site residence times, higher-ranking
females would be able to spend longer at the resource than lower-ranking females. Analyses showed that coalitions were rare
relative to some other Old World primate species, but females had linear dominance hierarchies. We found that, contrary to
expectation, fruit was not associated with more agonism and did not involve long site residence times. However, bark, a food
with a long site residence time and potentially high resource value, was associated with more agonism, and higher-ranking
females were able to spend more time feeding on it than lower-ranking females. These results suggest that higher-ranking females
may benefit from higher food and energy intake rates when food site residence times are long. These findings also add to accumulating
evidence that food site residence time is a behavioral contributor to female dominance hierarchies in group-living species. 相似文献
143.
When eggs hatch asynchronously, offspring arising from last-hatched eggs often exhibit a competitive disadvantage compared
with their older, larger nestmates. Strong sibling competition might result in a pattern of resource allocation favoring larger
nestlings, but active food allocation towards smaller offspring may compensate for the negative effects of asynchronous hatching.
We examined patterns of resource allocation by green-rumped parrotlet parents to small and large broods under control and
food-supplemented conditions. There was no difference between parents and among brood sizes in visit rate or number of feeds
delivered, although females spent marginally more time in the nest than males. Both male and female parents preferentially
fed offspring that had a higher begging effort than the remainder of the brood. Mean begging levels did not differ between
small and large broods, but smaller offspring begged more than their older nestmates in large broods. Male parents fed small
offspring less often in both brood sizes. Female parents fed offspring evenly in small broods, while in large broods they
fed smaller offspring more frequently, with the exception of the very last hatched individual. These data suggest male parrotlets
exhibit a feeding preference for larger offspring—possibly arising from the outcome of sibling competition—but that females
practice active food allocation, particularly in larger brood sizes. These differential patterns of resource allocation between
the sexes are consistent with other studies of parrots and may reflect some level of female compensation for the limitations
imposed on smaller offspring by hatching asynchrony. 相似文献
144.
Ting Chen Yingying Zhao Xiaopeng Qiu Xiaoyan Zhu Xiaojie Liu Jun Yin Dongsheng Shen Huajun Feng 《Frontiers of Environmental Science & Engineering》2021,15(2):33
145.
A mathematical model of the individual budget of a spawning female of the copepod Acartia grani (Sars) has been used to simulate the time-scale of egg production over various external forcings (or inputs) of food fluctuation conditions. The budget matter in the body of the copepod females is distributed through four compartments: the whole digestive tract (globally named as gut), the hemolymph (which include the body fluid with available nutriments for the organs), the structural body weight, and the gonad. This small calanoid species does not carry lipid reserves but cumulate some labile reserves in its body, according to food availability. The model results show how the continuous spawning varies with food fluctuations, and suggest the mechanisms inducing the delay of response to starvation by using the metabolic reserves. Three different patterns in egg production response are observed: food fluctuations with frequencies below 12 h have no effect on egg production; food fluctuations of 12 h to 5 days induce synchronous egg production fluctuations; beyond 5 days the strong physiological changes induced by long starvation durations create delays in the responses to food replenishment. The available data of cultivated cohorts under laboratory conditions are used to validate the model. The properties underlined by the model, in particular its weak capacity to respond to starvation, allow explaining A. grani distribution in specific habitats. Different experimental protocols for complementary experiments are proposed to complete the model validation in other forcing conditions. 相似文献
146.
Jason S. Link 《Ecological modelling》2010,221(12):1580-1591
The widespread use of ecological network models (e.g., Ecopath, Econetwrk, and related energy budget models) has been laudable for several reasons, chief of which is providing an easy-to-use set of modeling tools that can present an ecosystem context for improved understanding and management of living marine resources (LMR). Yet the ease-of-use of these models has led to two challenges. First, the veritable explosion of the use and application of these network models has resulted in recognition that the content and use of such models has spanned a range of quality. Second, as these models and their application have become more widespread, they are increasingly being used in a LMR management context. Thus review panels and other evaluators of these models would benefit from a set of rigorous and standard criteria from which the basis for all network models and related applications for any given system (i.e., the initial, static energy budget) can be evaluated. To this end, as one suggestion for improving network models in general, here I propose a series of pre-balance (PREBAL) diagnostics. These PREBAL diagnostics can be done, now, in simple spreadsheets before any balancing or tuning is executed. Examples of these PREBAL diagnostics include biomasses, biomass ratios, vital rates, vital rate ratios, total production, and total removals (and slopes thereof) across the taxa and trophic levels in any given energy budget. I assert that there are some general ecological and fishery principles that can be used in conjunction with PREBAL diagnostics to identify issues of model structure and data quality before balancing and dynamic applications are executed. I humbly present this PREBAL information as a simple yet general approach that could be easily implemented, could be considered for further incorporation into these model packages, and as such would ultimately result in a straightforward way to evaluate (and perhaps identify areas for improving) initial conditions in food web modeling efforts. 相似文献
147.
148.
We built a trophic network based on a matrix of interspecific trophic relationships to assess the role of elasmobranch fishes in shaping community structure of the Gulf of Tortugas in the Colombian Pacific Ocean. We analyzed diet similarities to define trophic components (nodes) - rather than taxonomical groups - in the network. We evaluated the ecological function of species or trophic entities through topological analysis of their structural importance in trophic networks by applying one local and several mesoscale network indices. We found that top predatory elasmobranchs play an important ecological role in top-down control and in propagating indirect effects through the system owing to high values of the node degree, centrality and topological importance indices. However, invertebrates and teleost fishes had higher connectivity and topological importance than other elasmobranchs in the network before and after removal of top predators from the system. Results from our study thus suggest that elasmobranchs at intermediate trophic levels - commonly referred to as “mesopredators” - are not so important in all complex coastal ecosystems as previously reported. 相似文献
149.
Steven L. Lima Patrick A. Zollner Peter A. Bednekoff 《Behavioral ecology and sociobiology》1999,46(2):110-116
In socially feeding birds and mammals, as group size increases, individuals devote less time to scanning their environment
and more time to feeding. This vigilance “group size effect” has long been attributed to the anti-predatory benefits of group
living, but many investigators have suggested that this effect may be driven by scramble competition for limited food. We
addressed this issue of causation by focusing on the way in which the scan durations of free-living dark-eyed juncos (Junco hyemalis) decrease with group size. We were particularly interested in vigilance scanning concomitant with the handling of food items,
since a decrease in food handling times (i.e. scan durations) with increasing group size could theoretically be driven by
scramble competition for limited food resources. However, we showed that food-handling scan durations decrease with group
size in an environment with an effectively unlimited food supply. Furthermore, this food-handling effect was qualitatively
similar to that observed in the duration of standard vigilance scans (scanning exclusive of food ingestion), and both responded
to changes in the risk of predation (proximity of a refuge) as one might expect based upon anti-predator considerations. The
group size effects in both food-handling and standard scan durations may reflect a lesser need for personal information about
risk as group size increases. Scramble competition may influence vigilance in some circumstances, but demonstrating an effect
of competition beyond that of predation may prove challenging.
Received: 22 September 1998 / Received in revised form: 1 February 1999 / Accepted: 14 February 1999 相似文献
150.
Food security is a global concern affecting even highly developed countries. Ongoing globalisation of food systems, characterised by trading interdependencies, means that agricultural production can be disrupted by climate change, affecting food availability. This study investigated Sweden’s food security by identifying major food import categories and associated trade partners (using the World Integrated Trade System database) and vulnerability to frictions in trade deriving from climate change. Vulnerability was assessed through three indicators: exposure based on diversity of sources, dominance and direct trade from supplying countries; sensitivity, assessed using the Climate Risk Index, and adaptive capacity, assessed using the Fragile State Index. The results revealed that Sweden’s grain imports may be most vulnerable, and animal products least vulnerable, to climate change. Management strategies based on this preliminary assessment can be developed by integrating climate vulnerability deriving from food trading into the ‘Gravity’ model, to improve prediction of trade flows.Supplementary InformationThe online version contains supplementary material available at 10.1007/s13280-021-01623-w. 相似文献