Resource Partitioning

The distribution and abundance of thirteen species of regular
sea urchin were assessed on Sosoikula and Nukubuco reefs, Fiji. Their
morphology and behavior were contrasted relative to wave activity,
water depth, substratum composition, food, and predation through all the
reefs zones. Densities and relative densities of species in each zone were
determined and their significance tested relative to the species distribution.
Results indicated species associations with different reef areas, thus
habitat preferences, which reflected species’ competitive abilities and
resource partitioning. Echinometra mathaei was the most prolific and
adaptable species, having the greatest densities in all zones. Peak mean
densities occurred in the mid back reef area on the echinoderm flat (2.64
ind. m–2), comprising 93.6% of all echinoids found. Diadema savignyi
and Diadema setosum were found at maximum densities in the boulder
zone, utilizing the narrow elevated crevice space. Both these species of
Diadema showed an increase in test diameters and spine lengths from
the reef crest to the hard coral bommies, proportional to the increase in
observed crevice size. Echinothrix diadema and Echinothrix calamaris
(brown color morph) demonstrated a similar trend, but with continued
growth-related migration to the Porites and soft coral zone. The white
color morph of E. calamaris showed no apparent association between
size distribution and crevice space. This was due to behavioral adaptations,
where both juveniles and adults aggregated together in the few
very large crevices found. Algal and seagrass species distributions
appeared to have only a moderate influence on echinoid species distributions,
as most species diets appeared broad within habitat. Predation
pressure was assessed to be relatively low, with greatest predator densities
on the fore reef (0.24 ind. m–2). Refuge quality and availability,
moderated by predation, combined with different echinoid morphologies
and behaviors, determined species distributions through the reefs varied
habitats.

This thesis is a result of fieldwork on foraging ecology of Afrotropical stingless bees in Uganda. This is because most studies on stingless bee ecology are largely based in South America and South-east Asia and have ignored the aspects of Afrotropical stingless bees. The central question is how the Afrotropical bees co-exist by partitioning their resources. Aspects of nesting behaviour of the stingless bees are presented in chapter 3. In BINP there are at least five stingless bee species belonging to two genera: Meliponula (four species) and Hypotrigona (one). The bee species nest in tree cavities, mud house wall crevices and underground. The relative importance of predation, food supply, nesting site and elevation affecting abundance of stingless bees were studied for meliponines in chapter 4. Predators were treated more comprehensively compared to previous field studies. Our figures for nest density for both the honey bee and the combined stingless bee species may agree with esti...

Mechanisms that favour the co-occurrence of morphologically and ecologically similar species in South America are potentially relevant, because two or more species often occur in sympatry. In the present study, we investigated possible mechanisms of resource partitioning between two sympatric species of foxes, the crab-eating fox Cerdocyon thous and the pampas fox Pseudalopex gymnocercus, in the National Park of Aparados da Serra in southern Brazil (29°10′S, 50°05′W). We considered three main niche dimensions – habitat, diet and time – and evaluated the overlap between the two species in these dimensions. We conducted the study from June 2000 to October 2001 in an area composed of open grasslands and Araucaria forests. We studied the foxes by using a combination of scat analysis and direct observation. A comparison of their diet indicated that it was very similar for both species in all seasons (Pianka's indexes ranging from 0.920 to 0.957). The most common food item for both species of foxes was rodents, followed by coleopterans, birds and plant remains (seeds and fruits). As expected by the niche-complementarity hypothesis, we detected differences along other niche axes. Pseudalopex gymnocercus seemed to occur only in open areas, including grasslands and dirt roads, whereas C. thous was more generalist in habitat use, occurring both inside and at the edge of forests. However, both fox species were common in grassland habitats, where they might compete for resources. The differences were more marked for activity time, with the crab-eating fox being significantly more nocturnal (circular mean of time of sighting=23:39 h, se=56 min) than the pampas fox (circular mean=19:56 h, se=64 min; Watson's F=6.06, P=0.02). We suggest that the larger C. thous could be limiting the activity of P. gymnocercus by interference competition.

Notice of Violation of IEEE Publication Principles"A Dynamic Distributed Diagnosis Algorithm for an Arbitrary Network Topology with Unreliable Nodes and Links,"by Pabitra Mohan Khilar and Sudipta Mahapatra,in the Proceedings of the International Conference on Advanced Computing and Communications, 2007. ADCOM, Dec. 2007, pp. 125-130After careful and considered review of the content and authorship of this paper by a duly constituted expert committee, this paper has been found to be in violation of IEEE's Publication Principles.This paper contains significant portions of original text from the paper cited below. The original text was copied without attribution (including appropriate references to the original author(s) and/or paper title) and without permission.Due to the nature of this violation, reasonable effort should be made to remove all past references to this paper, and future references should be made to the following article:"A Distributed Network Connectivity Algorithm,"By E. Procopio Duarte Jr. and A.Weber,The Sixth International Symposium on Autonomous Decentralized Systems, 2003. ISADS 2003 April 2003, pp. 285-292This paper presents a distributed network diagnosis (DND) algorithm for an arbitrary network topology where every node needs to record the status of every other nodes and links assuming the nodes and links are subjected to crash and value faults in a dynamic fault environment (the node's or link's status may change during execution of algorithm). The algorithm operates correctly in each connected component if the network is partitioned due to a set of faulty links or faulty nodes. The worst-case bounds for diagnostic latency is at most O(td) rounds where t is the number of dissemination trees and d is the diameter of the network. The proposed approach uses non-broadcasting method of message dissemination that has similar diagnostic latency with flooding [4] and similar message co- mplexity with Chinese Agent [14] method of message dissemination respectively.

The stable isotope ratio and seasonal changes in diet of two indigenous (Oreochromis mossambicus, Tilapia rendalli) and one exotic (Oreochromis niloticus) tilapiine cichlids in the subtropical Limpopo River, South Africa were investigated to determine patterns of resource partitioning. Stomach contents of O. niloticus and O. mossambicus indicated high dietary overlap across size class, habitat and season, with both species primarily feeding on vegetative detritus. However, stable isotope analysis revealed that the two Oreochromis species had different stable isotope ratios derived from different food sources. The relatively δ13C-depleted O. niloticus indicates a phytoplankton-based diet, while the δ13C-enriched O. mossambicus indicates a macrophagous diet dominated by vegetative detritus and periphyton. The high similarity in stomach contents and the interspecific differences in isotopic composition reveal fine-scale patterns of food resource partitioning that could be achieved through selective feeding. Tilapia rendalli was largely macrophagous and fed mainly on aquatic macrophytes and had a low dietary overlap with both O. niloticus and O. mossambicus. In the Limpopo River, detritus and algae are probably the most abundant food resources and the causal factors responsible for the observed patterns of resource partitioning among the tilapiines are usually difficult to ascertain. Fish may be able to perceive food resources in terms of the dynamics that determine their availability. Detailed studies of variation in food resource availability and fish habitat use within the system are needed to evaluate this hypothesis.

Timing side-channels represent an insidious security challenge for cloud computing, because: (a) massive parallelism in the cloud makes timing channels pervasive and hard to control; (b) timing channels enable one customer to steal information from another without leaving a trail or raising alarms; (c) only the cloud provider can feasibly detect and report such attacks, but the provider's incentives are not to; and (d) resource partitioning schemes for timing channel control undermine statistical sharing efficiency, and, with it, the cloud computing business model. We propose a new approach to timing channel control, using provider-enforced deterministic execution instead of resource partitioning to eliminate timing channels within a shared cloud domain. Provider-enforced determinism prevents execution timing from affecting the results of a compute task, however large or parallel, ensuring that a task's outputs leak no timing information apart from explicit timing inputs and total compute duration. Experiments with a prototype OS for deterministic cloud computing suggest that such an approach may be practical and efficient. The OS supports deterministic versions of familiar APIs such as processes, threads, shared memory, and file systems, and runs coarse-grained parallel tasks as efficiently and scalably as current timing channel-ridden systems.