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Stream is undoubtedly essential for the river ecosystem. It is the source of water for the river as well as the groundwater. At the same time, it is essential to study the macroinvertebrates to know their role on the food web. But how it is beneficiary to humans or what is the social impact of this kind of study?
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Chemical parameters show the condition at the moment. In running water, it requires frequent measurements or mixed tests to get an overview of time. Macroinvertebrates respond to long-term conditions, and can, for example, be knocked out by an acute discharge, which is not captured by chemical sampling. In addition, biological indices require relatively little equipment and resources.
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What problems will arise if there is either an increase or decrease in the number of any component in a food chain or a food web?
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Imbalance the ecosystem.... causes deleterious effect on survival of every living things.
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I have a dataset composed of aphid and parasitoid abundances captured in Moericke traps on a monthly scale for 10 years. As I do not have data on parasitism, but on the occurrence of aphids and parasitoids, I cannot use common trophic networks. In this way, I think I could explore some community-level relationships through correlation-based networks. However, I would like to know if there is any impediment to using this approach or if anyone has already used it.
Grateful!
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It is mainly studies in microbiology that have applied these methods, and I know of no study that has done this on host-parasitoid or prey-predator networks. I think the general principle is the same though.
You will probably have to think about applying a time-lag in your models, to take into account the development time of parasitoids in aphids. I enclose 4 publications that have studied these questions, with models that are relatively easy to implement in R.
Of course the main issue would be that you cannot directly link parasitoid abundances to the biological control service provided (correlation is not causation).
We can continue to discuss by mail if you want, and see what we can do together on this subject if you are interested.
Kevin
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For example, I want to explore the relationships between soil nematode communities and microbial communities under different treatments, including relationships of functional and taxonomic composition between each other. Nematodes and microbes belongs to different trophic levels, i.e., bacterivore nematodes feed on bacterias; fungivore nematodes feed on fungi; herbivore nematode feed on plant roots; and omnivore nematode prey on bacterivore, fungivore, and herbivore nematodes. In conclusion, which statistical tools are suit for analysis of relationships in complex soil food web?
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you can use the Orthogonal partial least squares discriminant analysis (OPLS-DA) is a supervised multiple regression analysis for identification of discrimination between different datasets, or use some kind of machine learning algorithm, here are some manuscripts:
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Hello All! I am working on a project that uses stable isotope analysis (C and N) to look at the diets of California reef fishes. I am going to be collecting Liver and White muscle tissue. It was suggested to me to use 20ml borosilicate glass scintillation vials (urea caps with polyurethane lined caps/not foil lined) for my tissues. I will be freezing the tissue samples in the vials and drying them in a 65C drying oven in them as well. The issue I am running into is that every brand of vials are back ordered for about 4 months no matter where I look.
So I wanted to see if 1. Anyone in the southern California/greater LA Area had vials I could buy off of them to use. Or 2. If anyone knew of a substitute I could use. It has been suggested that I could hand make aluminum foil packets, pre combust them, and store/dry the tissue in those. However, I would prefer the glass vials for both, organization/storage sake as well as I will eventual be grinding the powder into a powder and vials would be less likely to fail with the powder.
Thank you in advance for any advice!
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Thermo Scientific ™
EPA, COT and scintillation vials and caps
Reference: B7950-B
Related applications: Industrial Chromatography
Choose from one of the 100, 200 (pre-cleaned), or 300 (pre-cleaned and certified) levels of clear glass vials or amber EPA vials containing a total capacity of 20ml and 40ml. Assembled kits contain vials with pre-attached caps and septa..
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So far, most of methods about inferring the trophic or ecological interactions take account of the circumstance of aquatic ecosystem. Many methods have emerged, such as the method based on body size (Gravel and Poisot et al., 2013) and the method based on published data (Gray and Figueroa et al., 2015). However, these methods have many limitations when applied to terrestrial ecosystems. Are there any generic methods to infer the trophic interactions in terrestrial ecosystems?
Any helpful answers would be appreciated!
Best wishes.
Reference
Gray, C. and D. H. Figueroa, et al. (2015). "Joining the dots: An automated method for constructing food webs from compendia of published interactions." Food Webs 5: 11-20.
Gravel, D. and T. Poisot, et al. (2013). "Inferring food web structure from predator-prey body size relationships." Methods in Ecology and Evolution 4 (11): 1083-1090.
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Hi Hao Xiyang , kindly check whether the below link is helpful for you.
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Groups of macro-invertebrates based on a food web exist, simplistically, species A always predates on species B. So, no species B means no species A. With phyto-social communites these interactions are, to my knowledge, not present. So, species co-occurrence is not connected to food web interactions between species. Lets extent this example to the occurrence of macrophytes. Consider a large lowland river with no hard substrate (stones, rocks etc.) We can find E. nuttalli, M. spicatum, N. lutea and S. emersum. We arbitrarily call this a lowland community. Now we throw some rock and stones to stabalize the banks of this river. After some time F. antipyretica starts to grow. Yet, F. antipyretica is not considered to belong to a lowland community, since it is often observed upstreams in mid mountain regions or smaller rivers (with hard substrate due to higher flow velocities and turbulent waters). Thus, F. anitpyretica only started to grow here because it now has hard substrate, not because the other species are present . There, seems to be no existing community structure, since F. antipyretica just starts to grow there because the environment provides the means to do so and it can compete with the other species. The statement 'Everything is everywhere, but, the environment selects' (Baas Becking, 1934; de Wit and Bouvier, 2006), makes sense focusing only on macrophytes (not the interaction with predators or species needing certain macrophytes). For macrophytes, external factors "favor" the occurrence of certain species over others. Species that have similar "preferences" and traits are "selected" over others. From a deterministic standpoint, if we new everything we could predict species occurrence. Yet, we cannot, so we just group them together with species seemingly occurring often together. Certainly, lowland communities can be observed, but a slight change in the environmental factors will change these communities. These communities of species are only observed because of the simultaneous occurrence of often correlated environmental factors under "natural" conditions. Hence, large lowland rivers often have no hard substrate, while upstream rivers do. We, as humans have said, this is a community, since this is the "natural" state of an environment, while these species do not recognize this particular delineation. Does this suggests that delineation of phyt-social communities of macrophytes is just an outdated concept, since macrophyte species do not form communities, but simply occur there because they can? The fact that we can show that these species are often present in groups with ordination methods or cluster analysis, does not make it a community, just a group of species with similar "preferences" and "traits". The first result I get on google searching for a definition of community (definition community biology) results in "Community, also called biological community, in biology, an interacting group of various species in a common location (https://www.britannica.com/science/community-biology)". But, this definitions cause an itch with me regarding macrophytes. The definition does not really fit with my idea of macrophyte communities. I cannot really concretely and shortly explain why, but I hope the example above gives some idea. Either the definition just does not apply to communities of macrophytes, macrophyte communities doe not exist, or I have a wrong idea of macrophyte communities. Someone has any other point of view on this "issue", or can shortly describe what I am struggling to shortly explain and understand.
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I think what you are grappling with is the old argument between Gleason and Clements and their followers about what constitutes a community. We can define a community as simply a bunch of species growing in the same place at the same time, a Gleasonian approach, without requiring anything more. The idea of a structured "community", in this view, is an illusion; we impose the idea on nature because we tend to see the same species growing together in similar environments. But as your example points out, a small change in conditions can lead to a different "community".
The Clementsian view would be that similar conditions promote similar groups of species, which therefore grow together frequently and have done so for a long time. Inevitably, these species interact with each other, especially through competition, through which some species may be eliminated and others retreat to realized niches where they do not seriously compete with other species. Hence, in time we have a more or less fixed community of species that fit together like pieces of a jigsaw puzzle, each with its place, and different community arise in different physical environments. A sandy lake shore reliably supports one kind of community, a rocky shore another. Species interactions remain pivotal to the structure of the community, even if we cannot see them.
The prevailing view these days, as far as I know, is that the world is more Gleasonian than Clementsian. Species interactions (competition) do structure communities; but disturbance, recolonization and environmental change are so commonplace that most "communities" are mostly random groups of species that happen to favour the same habitat. So, as in your example, adding rocks to the bottom promotes a different set of species. There may be competition among them, but before they get that sorted out, by competitive exclusion or habitat partitioning, the world changes again.
Sorry for the long answer. I hope that sheds some light.
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Hi food web colleagues, diet experts...etc
Our last project started from the crazy idea to build a comprehensive benthic topology food web for the whole North Sea. It quickly seemed impractical for only a few human-beings as we lack data for most non-commercial species. It took almost two years to focus on 152 species, project that got reduced to 50 or so species for practicality.
We still want to go for it but I think we need to find the right people who might have the diet data we need or know where to find them (in situ, lab feeding experiments, published or unpublished data, or inference from other species).
Do you have diet information on species in the North Sea? Know someone who does? We could start from there.
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Hi Pierre!
How it's been since Villefranche?
I do not know if you plan to include zooplankton in there but i've got that paper from the english channel (but i think it is fairly applicable to north sea at least in the great lines):
(i'm sorry for the colors they are ugly but i was begining with R graphics!)
If you want to go further you can look at the references cited in there or you can contact me i should be able to point you to the main references on zooplankton feeding ecology in the north sea
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I'll have 2 days doing practical work with R. What do you think I'll have time to do? I was hoping to spend one day on inverse analysis using LIM-Solve and then one day on ecological network analysis using enaR. But to do so, I need a very simple example: does someone have such a simple case?
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enaR: Ecological Network Analysis with R Matthew K. Lau∗ David E. Hines† Pawandeep Singh‡ Stuart R. Borrett§
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Hi,
I am moving from analyzing food web network to bipartite network and I was wondering if anyone knew where to start? What books/articles I must read?
I am especially interested in the metrics I could use (modularity among others). Have an overview of those metrics...etc
I screened through the 'bipartite' package in R.
Thanks in advance,
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In our recent published book you can find some good chapters related to this topic. Please check it out:
Dáttilo, W. and Rico-Gray, V. (Eds.) (2018). Ecological Networks in the Tropics: An Integrative Overview of Species Interactions from Some of the Most Species-Rich Habitats on Earth. ISBN: 978-3-319-68227-3. Springer. 201p.
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I'm currently working on OM sources fueling fish communities in the North Sea. I have a dataset of C and N isotopic ratios for fish and I would like to include benthic, pelagic and riverine OM end-members in an isotopic mixing models. I have values for benthic and pelagic productions, but I can’t find papers presenting isotopic ratios for main rivers flowing into the North Sea. Is someone aware of such dataset?
Thanks in advance
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Thanks Helena and Moussa for your help !
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With the widespread using of barcoding or metabacording and genomic sequencing, many cryptic species, which morphological similar butgenetic difference largly, were frequently reported in many groups and ecosystems. Especially for Tropical insect.
 It seems cryptic species should be very common, In a recent work, Janzen et al.(2017 PNAS) said maybe 10-20% traditional morphologically single species may turn out to be two or more. If that is ture. It will definitely increase the absolute species diversity. Meanwhile, cryptic species may be a common phase in speciation.
 What other means of cryptic species to speciation process, food web, plant-animal network and ecological serves? Whether crypitic species will changge some parts of  our understanding fundermentaly on above concepts?
 Furthermore, what kind of groups have a relatively higher ratio of cryptic species, whether some different pattern between generalist species or specialist species in ecology network?
 I study the coevolution between fig tree and fig wasp, in which many cryptic fig wasps were reported. That is also the pattern in many other systems. So I interest How cryptic species arose and what it means in ecology and evolution.
Thanks in advance for anyone suggestions and comments!
 Gang
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I think this is a very interesting question. In the interest of clarity, I think that we should consider debating two questions when talking about cryptic species:
1. Are cryptic species 'mere' taxonomic artefacts?
2. What cryptic species mean in ecology, conservation, biogeography and evolution? (the question considered here).
1. Are cryptic species 'mere' taxonomic artefacts?
Not all of them. A problem that we encountered in a literature survey (available here ). Is that many cryptic species complexes are diagnosed with very few evidence. For instance, most papers using DNA provided only mitochondrial data is considered (despite its limitations), and most papers do not focus on morphology. As such, many cryptic species complexes are diagnosed poorly and the term became somehow a 'buzz word'.
The other problem is that the most cited paper in the cryptic species literature ( ) focuses on the "taxonomic history" of the species complex, rather than on biological phenomena. We have analysed this issue providing evidence that focusing on the taxonomic history leads to the diagnosis of cryptic species even when morphological differences occur ... or does not permit the diagnosis of cryptic species even when there are no morphological differences in the complex ( ). In that online book chapter we provide two cases where that occurs.
Considering this, in my opinion, while many cryptic species complexes are not well diagnosed, there is still evidence that "morphologically identical or quasi-identical species" (as suggested by ) occur. A good example is the Stygocapitella species complex ), the Cavercnamella species complex ( ) or the Mastigias species complex ( ).
2. What cryptic species mean in ecology, conservation, biogeography and evolution? (the question considered here).
Considering that cryptic species complexes are biological entities, the decceleration of morphological evolution is an interesting phenomena. Bickford et al, and Bernardo make a very interesting case for conservation biology suggesting we're overlooking much diversity and potentially need to conserve different areas ( ; ). For biogeography, we found that the discovery of cryptic species leads to the diminuishing of species-distributions. This is important for, for instance, marine organisms which distribution is largely unknown or paradoxical ( ). Also, as part of my thesis, I have been arguing that cryptic species can impact ecology (niche partitioning theory), evolution (deceleration/acceleration of morphological evolution) and paleontology (is there a link between cryptic species stasis?) . I personally think that understanding the underlying factors leading to the deceleration of morphological divergence (as seen in cryptic species complexes) is a very pertinent and interesting question.
PS: I provide many links to my research as this has been the main topic of my dissertation. Apologies for the shameless self promotion, but I wanted to contribute meaningfully to this debate
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I have data of an antagonistic network (predator-prey) and also have data about prey availability in the environment. I would like to incorporate this data (prey availability) in network analysis. Is it possible?
Thanks!
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Hello Dr. Davis,
I know that networks are related only to realized connections among species, however, in some trophic networks, the prey availability may influence some interactions. For example, a prey type I can be abundant in a network, favoring the major number of interactions, and another prey type II can be rare, so presenting a few numbers of interactions. Not necessary the predator prefer the prey type I, the high number of interactions is related to the bigger abundance of this prey in the environment than prey II. Thus, if we consider the abundance of preys, the prey type II is preferable than prey I, but in networks metrics, this can be occulted. I would like to add in networks this information or maybe ponder networks metrics by prey availability.
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What are the effects of transgenic DNA in the soil food web? What consequences, if any will these have on soil health?
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Risks are associated with the impact on non-target organisms of the technologies. Studies related to this topic have shown that there is no adverse effect due to the implementation of GMOs on soil arthropod populations. To analyze the possible effects of the release of GMOs in our agricultural systems, we must put them in context in relation to the impact that are generating the technologies that can be substituted by the implementation of GMOs.
The implementation of any technology involves the assessment of risks and the implementation of tactics to mitigate the possible risk.
 
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Ever increasing population, urbanization and modernization are posing problems of sewage disposal and contamination of surface waters like lakes. Species and habitat dynamics in the face of climate change are complex and have many aspects. Increased temperatures and CO2 concentrations will have an effect on different processes such as photosynthesis, respiration and decomposition and generally speed up these processes. Climate-induced changes in ice cover period, thermal stratification and nutrient availability and longer growing seasons affect species composition and food web structures.
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"What methods of analysis can I use for water quality assessments?"
Basically there are Biological, Physical and Chemical parameters to asses water quality.
Best thing to new starter is to refer USEPA or your county effluent discharge standards.
In case you want to analyze the impacts due to polluted water etc., there are impact assessment methods such as ISO.
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Who is interested in discussing the interrelationship between biodiversity and vector-borne diseases. Global Change, Biodiversity Loss and Human Health are obviously linked in many ways, but there is no clear proof about the specific processes. Insect vectors for pathogens such as arboviruses would be a nice field for investigation because they are ectothermal and they are part of the food web and thus influenced by biodiversity.
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Alterations in biodiversity can affect disease transmission either through their influence on vectors of disease, or more directly on their influence on the disease causing organisms themselves. Changes in landscape diversity, due to agriculture, have resulted in the spread of human diseases. For instance, the introduction of Jhum cultivation (slash-and-burn agriculture) into wet tropical Africa resulted in an increase in malaria which in turn increased the occurrence of 'sickle-cell anaemia'. Physically damaged reefs are often invaded by the dinoflagllate Gambierdiscus toxicus, which causes 'ciguatera' in human beings. 
Please also have a look at these useful RG links.
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I'm researching New England cottontail diet selection at the population level and am looking for an efficient way to run Manly's G-test. Any help would be greatly appreciated!
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Wendy, I would like to ask you a question: Do you have a copy of the book ‘Resource selection by animals’ (Chapman, 1993), by B F J Manly et al.?
By the way, Manly had (or has) an active page here at RG.
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Do you know any published paper focusing on feeding interactions (predation, competition, niche partitioning) between alien/invasive top predators originating from different areas when they co-occurr in a new area?
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Is this the kind of thing you're looking for ?
Mesopredator Management: Effects of Red Fox Control on the Abundance, Diet and Use of Space by Feral Cats. Robyn Molsher, Alan E. Newsome, Thomas M. Newsome, Christopher R. Dickman. 2017. https://doi.org/10.1371/journal.pone.016846
There's quite a lot of literature on this combination (cats and foxes in Australia) and also foxes and dingo. This paper will get you into that literature.
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I want to analyse the diets of infaunal invertebrates from a deep-sea methane hydrates site. The organisms had been preserved in 10 % formalin and then transferred to 70 % ethanol for about 4 years now. I know this preservation method affects the carbon stable isotopic signature and, depending on the organisms, the nitrogen stable isotopic signature too. But I'm having some trouble finding information on the literature about the effects of preservation on sulfur stable isotopes.
Thanks!
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Thank you all for your answers!
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My project attempts to explicitly include humans as driver nodes within complex food webs, as opposed to simply being considered external factors. I do not know if such a specific model exists, but I am hoping to find something that links market price, labour, equipment, regulations, ect. with the amount of fish caught.
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Hi Alexandra,
you might wish to look into the approaches of Rashid Sumaila and his group at UBC, Vancouver, mostly using game theory to interpret findings. Reg Watson, back in Australia is developing a global price database for fish and marine products. These groups give very useful leads.
The criticism of "the tragedy of the commons" that underlies much of modern policy, whether it's ITQs or other allocation proposals, is that it's too narrow a definition - see work by Ostrom and others. See also
Beyond the Tragedy in Global Fisheries. By D. G. Webster. Cambridge, MA: The MIT Press, 2015, 468 pp., hardcover. ISBN 978-0-262-02955-1. and a recent review of the book by J.K. Abbott
Hope that helps as a starting point. Greetings, Cornelia
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I think the actual question here is "how do you identify keystone species from a food web"? Do you always need the biomass data or knowing the whole food web is enough?
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What's changed in our understanding of the keystone species concept? Of course top level predators can be keystone species! Paine's original example was the sea star, Pisaster ochraceus, and sea otters, wolves and jaguars have all, also, been described as keystone species. The latter two are clearly apex predators. I won't comment on jaguars, but the evidence for wolves as keystone predators seems quite strong. So, I'd argue that high level or apex predators CAN be but are not always keystone species.
I wonder if interaction strength could be used as a (partial) measure or indictor of a keystone species. See for example
Ripple et al. Status and Ecological Effects of the World’s Largest Carnivores. 2014 Science 343 (6167): 1241484 DOI: 10.1126/science.1241484
Sala, E. & PKD Dayton. 2011. Predicting strong community impacts using experimental estimates of per capita interaction strength: benthic herbivores and giant kelp recruitment. Marine Ecology 32: 300-312 DOI: 10.1111/j.1439-0485.2011.00471.x
Sala, E. and M.H. Graham. 2002. Community-wide distribution of predator-prey interaction strength in kelp forests. Proceedings of the National Academy of Sciences 99: 3678-3683.
Estes, J.A.; Tinker, M.T.; Williams, T.M.; Doak, D.F. (1998-10-16). "Killer whale predation on sea otters linking oceanic and nearshore ecosystems". Science. 282(5388): 473–476. doi:10.1126/science.282.5388.473.
I'm also intrigued by the possibility that the "interaction" need not be a direct, trophic interaction:
Gómez, José M.; González-Megías, Adela (2002). "Asymmetrical interactions between ungulates and phytophagous insects: Being different matters". Ecology. 83(1): 203–11. doi:10.1890/0012-9658(2002)083[0203:AIBUAP]2.0.CO;2.
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Micro-nutrients play an important role in determining which species of phytoplankton grow. If micro-nutrients are abundant, Diatom Algae grow and this strengthens the food web. So studying micro-nutrients is very important.
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i recommend to study about micro and macro nutrients .
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Dear friends,
The question as I said in the title, I'm not sure about what problems we will get in troubles, If we use the stable isotope approach.
I hava already read some papers about the fish stocking migration between the different habitats.
I think the most problem is that the different tissues hava the different rate of metabolism, for example, the liver and blood cell have very fast rate, just few days, and the white muscle, fin, or bone of fish can present a long period of feeding habit, and the stable isotope values can present previous habitat information. Moreover, the size of fish we collect may be also can influence the result of the stable isotope values, but I'm not sure about it.
you guys can give me some suggetions or advices about the question as much as you konw, if so, thank you very much.
Regards,
Xie Bin
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Hello, your question is very general, the problems in the use of isotopes will depend on the type of isotope you are using. I recommend that you read this book that will help you answer all your questions.
Hobson, K. A., & Wassenaar, L. I. (2008). Tracking animal migration with stable isotopes (Vol. 2). Academic Press.
Viljoen, G. J., Luckins, A. G., & Naletoski, I. (2016). Stable Isotopes to Trace Migratory Birds and to Identify Harmful Diseases: An Introductory Guide. Springer.
I send it to you in attached
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In aquatic ecology research, the relationships between different trophic level are important. Stable carbon and nitrogen isotopes analysis(SIA) are widely used to ravel the interactions between linkages in food web.
The biomass and quantity of top level organisms in food web are always low, and the collection metod requires dead individuals, and which could collect tissue samples easily.
Currently, a large proportion of top predators are rare or threatened. Few articles use the non-lethal methodologies which collect the blood or fins.
Why the non-lethal method is not widely used?
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Such methodologies are widely used, but the resolution is poor. I spent several years doing a master's using fatty acid analysis to differentiate between food sources in Atlantic Tarpon in the early 2000's. It worked...sort of. Here's the thing, fatty acids in tissue are not just diet-related, they're biosynthesized and utilized at different rates based on physiological changes & stresses to the organism. The best paper at the time was produced by a lab in the far white north, and there was so much mathematical black magic used in the paper that few people who were doing the work at the time believed them.
Isotope work is even more vague than fatty acid analysis. Okay, as Sharon pointed out, sharks may feed in marine and freshwater biomes...but what does that really tell you? Not much! A gut-content study (they can be done non-lethally) can tell you what species are consumed specifically, rather than...over the last year or two the shark fed on saltwater and freshwater organisms. For example, gut content studies in Florida in the 1970's (I believe 1977) found that alligators were feeding on a variety of native fish, turtles, and mammals. The lab I worked in did a preliminary study in the mid-2000's on alligator diet using gut-content analysis and discovered that their diet had switched to 95% exotic fish species. Would an isotope study been able to catch the change? I'm not sure, but I know it's much cheaper and more accurate to have students sort through the stomach contents of an alligator to see what it ate compared to using fatty acids or isotopes to calculate a ratio. What are tiger sharks eating in SW Florida estuaries? Probably saltwater and freshwater organisms when they can get them. But the 8'1" tiger shark I examined had eaten saltwater catfish and batfish. That's more interesting than a vague trophic-level analysis.
Isotope and fatty acid analysis can be good tools IF you are only examining higher-level trophic interactions. If you want fine details, stick to the old, dirty, stinky, disgusting methods that work.
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I am aware of some work on the affects of anthelmintics on the fauna feeding on dung but was keen to find if wider work has been done on their effects on wider range of pasture insects and the consequence effects on species that feed on them in particular birds. Changes in land use are and to some extent predation are cited as causes of decline of some species of farmland bird, however for some the impact of veterinary medicines on food chains is also a possible contributor and I am keen to find out who and where such wok may have been carried out. Any thoughts welcome.
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Herbal remedies are the current focus of most livestock researches. indigenous knowledge on plants are being backed up with scientific evidences to provide ideal solutions for safe animal production
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In order for a plant to grow and thrive, it requires Carbon, hydrogen, oxygen, nitrogen, phosphorus and potassium. The former three are easily available from air, water and other sources, while the latter three are hard to come by. These nutrients are often found decay of plants or living organisms, while nitrogen is only available by recycling nitrogen from dead to living plants. That’s where fertilizers come into the picture, these provide the necessary nutrients in order to make the plants strong and thrive better.
In my opinion, the simplest way to distinguish between compost and fertilizer is to remember this: Compost feeds the soil and fertilizer feeds the plants. Fertilizer adds to the soil's nutrient supply, but instead of feeding the soil food web, the ingredients in fertilizers are intended to meet the needs of fast-growing plants.
What do you think about the differences between compost and fertilizers? Which one is better?
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 Dear Adel Oueslati
Thank you for your contribution.
I hope that this discussion could be helpful for all the researchers who are involved in the field of solid waste management.
Regards,
Ata
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I am working on food web stoichiometry and I'm looking for a literature on constrains that may be posed on the bees' development because of N and P scarcity in pollen. Herbivores in general are N and P limited. Is this also true for pollen eaters (pollen is a concentrated sustenance, rich in nutrients)?
Thanks in advance!
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Quite often in environmental-economic literature (e.g. The Economics of Ecosystems and Biodiversity) welfare theory is used to calculate the supply of "ecosystem services" in "natural capital accounting" (NCA)? 
I am interested in literature which views ecosystems in different ways, especially from a "network" perspective. For example, a food web or food chain seem to me to have network structures. Do you have any suggestions about the most important references in this field? 
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A recent review of ecological networks (Tylianakis and Morris 2017) may provide some information and references. It is focused more on network structure but it does bring up food webs and how structure and ecosystem functioning are related.
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 I just completed the shannon Wiener diversity index and calculated a score of (H)=2.154890613. The values range from 0 to 5, with common ranges usually between 1.5 to 3.5. Can I really say that the population is diverse? What other index should I use when getting a score like this? Thanks
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Hi, Ms. Kayla Tennant!
There are different indices that may be used to measure biodiversity. Based on information-theory, the Shannon-Wiener Diversity Index measures uncertainty in order to determine if a community is diverse. A high degree of uncertainty (H') would indicate high diversity since it would determine how harder it will be to predict the species of a randomly picked individual from a population. It is easy to calculate, however, it does not reflect the dominance or evenness of a population.
Other diversity indices that you may also utilize are the Simpson's Index, Berger-Parker Index, and Brillouin Index. 
The Simpson's Index works on the idea that high dominance would indicate low diversity. It measures the probability of dissimilarity of the population, thus, a highly similar population would indicate lower diversity. the index is evenness-sensitive, however, less sensitive to species richness or abundance.
The Berger-Parker Index quantifies the numerical importance of most dominant species, while the Brillouin Index are used in questionable sample randomness.
Biodiversity indices observe changes to richness and evenness between datasets. The type of index to use may vary, depending on the site discrimination, sample size, diversity component in question, and the overall use of the index. 
I attached a link that may help you on species diversity measures. I hope this helps! 
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I would like to calculate the isotopic food-web baseline for a group of zooplankton that I collected in the Indian Ocean. In the original survey I collected POM samples, but the isotopic signatures of these are all over the place and in some cases with values more enriched than the zooplankton itself. I would like to be able to determine the isotopic signature of the food-web base supporting the zooplankton at each site – there were clear differences in zooplankton d13C signatures between some of the stations.
I am therefore looking for an equation with which I could calculate the baseline of the food-web supporting the zooplankton that I collected.
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Thank you! I actually not even sure where the samples are, I have even moved countries since... I'll try and think of a different way to approach the data sets. Thanks!
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In the paper linked below a case study of a mason bee (Osmia bicornis) feeding on pollen is presented. We concluded that the growth and development and thus the fitness of the bee might be co-limited by the scarcity of N, K and Na in pollen. Cocoon production may be limited by a greater number of micronutrients. Since O. bicornis may experience limitations to the growth and development of its body and cocoon production because of the availability of certain elements in its food, the amounts of potentially limiting elements should be maximized during pollen collection by the adult female bee for its progeny.
Food nutritional quality is known to regulate populations of wild bees and may be a factor contributing to bee decline. In addition, specific micronutrients, especially Na and K, may be lacking in bee diets, thereby forcing bees to search for a balanced diet. The quality of the pollen diet has a known influence on the survival, physiology and life history traits of bees (of various taxa). These traits are all connected to fitness; therefore, pollen quality may influence bee foraging choices. Is it possible that the nutritional quality of pollen influences foraging behaviour and life-history traits of pollen-eaters? What do you think? 
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Indeed the variability of pollen nutritional value is related to environmental conditions only for euribionte - organism biologically versatile, adaptable to different environmental and nutritional conditions such as to permit the colonization of different habitats (contrary: stenobionte) - species. In particular conditions these forming so-called eco forms.
I am sorry, unfortunately I do not know a study to verify the hypothesis
Iuliana
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I'm working on source partitioning for two lake food webs. While working on quantifying the sources using SIAR, I have come across some difficulties.
Here are my problems:
First, zoobenthos are the consumers for my systems, and I'm trying to calculate the source portions as detailed as possible; therefore, the "consumers" is sorted into groups based on genus, and most of the time, there is only one sample for each group. When I tried to calculate them in SIAR, it turned out a warning as"
=============== READ THIS ===============
There may be some problems with this data.
Some of the standard deviations seem especially large.
Please check to see whether the target data lie outside
the convex hull implied by the sources.
SIAR rates the problem with this data set as:
Severe - possibly severely affecting results
========================================
" . I don't know which part of my data leads to the problem, the consumers or the sources? How should I do with it ?
Second, the convergence diagnostics shows results like follows:"
Worst parameters are ...
detritus-LG5 SD1G2 detritus-LG2 detritus-DG5 detritus-DG2 SD1G1
0.0007164114 0.0033956284 0.0034963043 0.0092774801 0.0251035281 0.0334041570
SD2G3 SD1G4 detritus-HG4 detritus-DG3
0.0372546252 0.0495544969 0.0624383672 0.1138505731
If lots of the p-values are very small, try a longer run of the MCMC. "
I don't quite get the meaning of those numbers, what do the p-values measures?
Third, when estimating the source portion, should I use mode or mean in the results?
Thank you very much! 
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I don't know which part of my data leads to the problem, the consumers or the sources? How should I do with it ?
I suggest you to apply the method proposed by Smith et al., (2013) (http://onlinelibrary.wiley.com/doi/10.1111/2041-210X.12048/abstract) to check if your model assumptions (TEFs, and the set of sources) are correct. Maybe you missed a source for certain consumers. Besides, you can check the TEF for 15N. The widely used 3.4 is generally wrong regarding benthic invertebrates (specially detritivorous) look at Vanderklift and Ponsard (2003). If you use the wrong factor then your consumers will probably be outside the polygon..
Additionally, whereas you often have n=1 why don´t you try to group species into guilds or Functional feeding groups? This could help you get some clear results. 
 
I don't quite get the meaning of those numbers, what do the p-values measures?
Andrew answered it.
when estimating the source portion, should I use mode or mean in the results?
I am not sure if you mean the output of model or your input data. If it is the output of the SIAR, I think that you should report the mean and the confidence interval. Your input is generally the mean. 
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It is widely accepted that the major factor affecting the evolutionary optimization of animal life histories is energy balance, therefore studies focus on the energy costs and benefits of adaptations, the efficiency of energy acquisition and investment, and limits to energy budgets. However, at the very least in heterotrophs, equally important seems to be the problem of maintaining stoichiometric balance.
There are two approaches in eco-evo studies that consider the matter balance as complementary to the energy balance: ecological stoichiometry and nutritional geometry. However, in my opinion, such studies are limited and after 30 years after Tilman's and Reiners' works (below), still "energocentric" point of view dominates in ecology and evolution, that carelessly underrates the need to balance the diet also in terms of the matter (including the Law of Conservation of Mass).
This is only my point of view, possibly the wrong one. I would like to ask all of you: what is your opinion?
My question was introduced as briefly as possible, don't hesitate to dig deeper and extend it!
Below I present four important studies related to the topic, just to start with.
Kind regards,
Michał Filipiak
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Hi,
The question is how to integrate the stoichiometric concepts into the field data recalculations calculation ? Now field hydrobiologist can use coefficients of tempreture dependend functional indices like respiration or production, and amadements on oxygen concentrtation. But how to calculate disbalance or lack???
Andrey
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Recent studies (below) showed that predators may need to optimize their diets concerning not only energy but also quality of matter eaten. However, according to common assumption, this is not intuitive (see papers below). What are your thoughts? Is it possible that predators are limited because of macro- or micro- nutrients concentrations in matter eaten? What about elements? Is it possible that for predators important are ratios other than traditional C:N:P, studied using the framework of ecological stoichiometry? What about K and Na? What about Zn:Fe ratio (these two elements compete for absorption sites)?
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Dear Uwe & Michal,
for my opinion you both are right, but important is scale and direct surroundings. Look, for ins. the famous Gause experiments. If you have to do with protists it can be very important what say Michal. Both compounds - I mean behavioral (meanwhile, experience) and physiological "compatibility" of prey present in some proportion for the every predator or semi-predator, but for cheetah experience orientate it when it has choice of victims, but if hungry will no possibility to select.
I saw ciliated infusoria from Dileptus (absolute predators!) genera that eat diatoms algae that should be absolutely inappropriate for it? So, may be as well important is the stage of attack on prey and physiological state of both?
If take into consideration hunting plants - like Nepenthes Rajah (e.g.) from Borneo, the pharmacy of an object is of dominated importance!
The very good explanation of how it works in compact manner gives Wolfgang Meyerhof & Sigrun Korsching in preface of perfect book
Chemosensory Systems in Mammals, Fishes, and Insects. © Springer-Verlag Berlin Heidelberg 2009.
And you can read their opinion of the main scientists in the field (12 person)..
Look attached file.
Andrey
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Dear All,
I'm looking for available literature data on concentrations of elements (in dry mass) in fresh and decomposed pine (P. sylvestris) litter, other litters, pine pollen (P. sylvestris), pollen of other anemophilous plants and organisms inhabiting forests floors (fungi, insects, molluscs, isopods, worms, millipedes, detritivores, various litter- and soil- dwellers, protozoans etc.). C concentration is of greatest importance for me, since it was rarely reported as % of C in dry matter (surprisingly, concentrations of other elements are easier to find). Also N and P are of great importance. Data on any other element would also be great. I've already found some literature but it is surprisingly scarce, so I will appreciate any additional data. If you know any paper related to the topic, please put a link below. Thank you in advance for your time and help!
Kind regards,
Michał Filipiak
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Hi,
I have data on Phragmites australis leave litter (green leaves and after litter fall). I am not sure if this could be of any help. The data are published in Flury and Gessner 2014 (Effects of experimental warming and nitrogen enrichment onleaf and litter chemistry of a wetland grass, Phragmitesaustralis). If they are of any help I could send you the raw data.
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As pointed by Greenfield (1999) and Roulston & Cane (2000), pollen is easily digestible: special adaptations are not needed since pollen grains may be simply destroyed mechanically or through osmotic shock. However there exist a belief that pollen is hardly digestible (mostly because of chemical protection by extracellular wall). Lots of invertebrates belonging to various groups are known to supplement their diets with pollen (even predators). So is pollen easily or hardly digestible? Do you know any papers related to this issue? 
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Dear all,
I would like to mention toxicity of pollen which plays a major role for oligolectic bees; see for example: Praz C.J., Müller A., Dorn S. (2008) Specialized bees fail to develop on non-host pollen: Do plants chemically protect their pollen? Ecology 89, 795–
804.
Klaus
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Past studies have resorted to the removal of a certain species to identify its effects on the food web. Is there a way to identify which predatory relationships are strong enough to cause the destruction of the food web without the haphazard removal of species? 
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Litter/soil dwellers (arthropods: detritivores and omnivores) feed on unbalanced food (mainly dead plant matter) that is scarce in some physiologically important nutrients. This food alone is insufficient as a source of needed biomass. It is known that fungi may supplement such a diet with nutrient needed by these animals. However it is very hard to find any specific data on how exactly this mechanisms works.
If an arthropod feeds on dead plant matter, what exact substances are scarce in its food? And how much of these substances may be given by fungi? Is it enough?
Do you know of any papers that give information on exact nutrients that are scarce in litter/soil and are given to the litter/soil dwellers by fungi in considerable amounts? 
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Thank you for your answer, Shilpa.
Energy (carbon-rich compounds are only source of energy, not biomass needed to grow tissues) is not the problem here, since it is relatively easily available for considered arthropods. The problem is matter needed for growth, development, body-building and maintenance (biomolecules rich in elements other than COH).
Excretion of specific substances by fungi is not the mechanism of diet supplementation. I meant that fungi themselves are diet supplements. They are eaten by arthropods and ‛give’ to the arthropods molecules composing fungal mycelia. They are so called ‛butter’ that covers ‛bread’ of carbon-rich, hardly digestible dead plant matter.
This is how it looks in theory. But how exactly this mechanisms works? What specific nutrients play main role here and what amounts of these nutrients must be eaten by the arthropods to make this mechanisms reasonable?
Kind regards! 
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I sampled plant-pollinator networks along a gradient. Using the R package 'bipartite' I calculated a set of network metrics. The 'niche overlap' of the pollinator level as well as the 'functional diversity' (measure of niche complementarity) of both plant and pollinator level show a decrease with the gradient. At first glance, this seems contradicting to me. Is this possible, and what could be the explanation?
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You say you sampled along a gradient, but along a gradient of what? Landscape complexity? Habitat size? This will influence the expected results in functional complementarity and niche overlap.
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My colleagues are working on feeding preferences of macro symbionts of feather stars. They gathered data on stable isotopes from both sea lilies and its symbionts(shrimps, crabs, ,polychaetes, myzostomida etc). The results are quite surprising and not easy to interpret, so we want to have some reference points. Some people (who work with stable isotopes) advise us, that it might be more useful to collect data on primary consumers (not primary producents) from our area to have such a reference point.
But than we realized, that it is not an easy task to find really specialized primary consumer on the coral reef, as there is little known about food spectrum of most coral reefs inhabitant and many of them are mixotrophic.
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Hi Yury,
first of all, it would be important to match the stable isotopes data with gut content info. The primary consumers you are studying are filterfeeders, so they won't we strictly primary consumers. They are filtering POM, and Bacteria too. Therefore, as you indicated, they are all mixotrophic and probably, when you plot C vs N, you get a cloud of all species mixed with the chrinoids. So, this cloud is your base of "primary consumers" perhaps you could try to go upper from there. Like crabs and snails feeding on them and fishes. But, again, only stable isotopes is a weak info. You can match not only with gut content but also diving observations.
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I am trying citations related to the idea that "diversity begets diversity." In particular, I am interested in finding examples of experiments where diversity has been manipulated at one trophic level, and then diversity of lower or higher trophic levels was measured as a response variable. I am not interested in experiments that have only manipulated diversity as presence-absence. I am more interested in experiments that have multiple levels of diversity. I'm looking for experiments like these: 
Haddad, N.M., Tilman, D., Haarstad, J., Ritchie, M., Knops, J.M., 2001. Contrasting effects of plant richness and composition on insect communities: a field experiment. Am. Nat. 158, 17–35. doi:10.1086/320866
De Deyn, G.B., Raaijmakers, C.E., van Ruijven, J., Berendse, F., van der Putten, W.H., 2004. Plant species identity and diversity effects on different trophic levels of nematodes in the soil food web. Oikos 106, 576–586.
Ogada, D., M.E. Gadd, R.S. Ostfeld, T.P. Young and F. Keesing. 2008. Impacts of large herbivores on bird diversity and abundance in an African savanna. Oecologia 156:387-397.
Thanks for any leads!
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Hi Grace,
I know of the study by Scherber et al. looking at the diversity of different species groups in response to a plant diversity treatment. This may be of interest for you.
Scherber, C. et al. (2010) Bottom-up effects of plant diversity on multitrophic interactions in a biodiversity experiment. Nature 468, 553-556.
All the best,
Christian
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I have a sizeable data base with mollusca and other specific fauna remains encountered in cold water coral communities. I have no direct evidence for relationships of carnivore to its food source (e.g. a photograph of a mollusk having dinner or mollusk stomach content analyses) but I have some circumstantial data that may prove it. An example:
I have 100 location samples analysed in detail on occurence of mollusks with a high confidence and of other fauna with less confidence. Molluscan carnivore A has been found in 10 stations, the likely food source sponge B has been identified in 15 stations. In 9 stations A and B are found together. The probability that A has been identified in a station is high say p(A)=90%. The probability that B has been observed is lower say p(B)=30%. Is there a statistical measure to prove or disprove a relationship? 
Thanks for your thoughts, Leon Hoffman
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Leon:
I recomend the next 3 papers about a proved method:  EcoPath with Ecosim
 Christensen, V., Walters, C., 2004. Ecopath with Ecosim: methods, capabilities and limitations. Ecological Modelling 172, 109–139.
Christensen, V., Pauly, D., 1992. ECOPATH II A. Software for balancing steady state ecosystem models and calculating network characteristics. Ecological
Modelling 61, 169–185.
Christensen, V., Walters, C.J., Pauly, D., 2005. ECOPATH with ECOSIM: a User’s Guide. Fisheries Centre, University of British Columbia, Vancouver (November 2005  ed., 154 pp).
They are cited by Neira et al in : Mechanisms affecting recovery in an upwelling food web: The case of the southern Humboldt, published by Neira et al in Progress in Oceanography 83 (2009) 404–416.  Thanks to Francisco Fernandez from Sernapesca to help answer.
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I am currently working with both SIAR and MixSIR to analyze food web data using three food sources and dual stable isotopes (C/N). Does anyone know about the restrictions of each of the two mixing models when the isotope data of the food sources are quite close to each other? I would like to hear some opinions about the differences in the models' function. And generally, would the restrictions of the number of food sources and the range of data be the same for both mixing models?
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SIAR has on additional residual error term per isotope axis used in the model. If you have consumer (mixture) data that is highly variable compared to your source (prey) data, you should use this added residual error term (SIAR). If your consumer data is relatively invariant compared to your sources, you should not. MixSIAR allows you to choose. Note, however, that we are in the process of publishing a new error structure (and will incorporate into MixSIAR) that can be used in both instances, and is thus to be used in nearly all cases.
Regarding the "erroneous" behavior of MixSIR ... it was actually the simulation code used in the critique, not the model, that was erroneous. See http://www.ncbi.nlm.nih.gov/pubmed/19245585.
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Concentrations of PCDD/F, DL-PCB and NDL-PCB are lower in zooplankton (primary consumers and lower-trophic-level invertebrates) than in phytoplankton (primary producers).
I’m interested in levels of these substances in zooplankton (e.g. copepods), especially from Mediterranean area. I found a few publications, some a bit dated.
In particular which concentrations can be considered of concern at this marine food web level?
many thanks
stefania
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Hello Stefania, you can take also a look at these two studies  performed in the MED, one focusing on biocumulation of PAHs in Zooplankton and the other on non-DL PCBs and OCPs in plankton. Maybe interesting for you. Regards.Javier
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Does anyone have experience turning large trophic webs into figures for publication? Smaller webs seem decently easy to do in something like photoshop, but for upwards of 100 interacting species, are there any good R packages (or other software packages) to accomplish this? 
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Cheddar is an excellent R package for food webs-for both visualisation and analyses.
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In spite of the classical notion that interspecific competition constrains niche width it is possible to envision circumstances under which it could cause niche width to increase.
For example, reducing the availability of a valuable resource forces an animal to compensate in some fashion: through increased exploitation of the other resources it currently consumes (as classical theory would dictate), or potentially, through exploiting new resources which can mitigate the loss. If more than one alternative resource is incorporated, an animal will have widened their niche as a direct result of interspecific competition.
Does anyone know of any studies which have shown such effects? Or any papers in which this or other possible ways interspecific competition could widen niche are discussed?
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Hi Amanda,
Have a look at the attached paper - should be useful to you.
Aleks
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Niger Delta is highly susceptible to pollution due to oil exploration and the nonchalant attitude of oil companies operating in the area towards Nigerian Environmental laws.
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I suggest that you consult the publications of the National Centre for Marine Geosciences. The centre is situated within Niger Delta University, Wilberforce Island, Bayelsa State. I know they have done quite alot on pollution along the coast from Lagos to Calabar. You can google them and link up.
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Can anybody help me to find toxicity and food web level toxicity of cyclopoid copepods on Copper?
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Hi, 
You may find some articles on toxicity of copper on copepods from Dr. Maria Moraitou - Apostolopoulou, like this one: "Acute toxicity of copper to a copepod", Marine Pollution Bulletin, Volume 9, Issue 10, October 1978, Pages 278–280, DOI: 10.1016/0025-326X(78)90612-4. http://www.sciencedirect.com/science/article/pii/0025326X78906124.
She is Professor of Zoology - Marine Biology at the University of Athens.
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I believe that the autochthonous primary production plays an important role in the transfer of energy through food webs in tropical streams.
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Both energy inputs are important for streams, but autochthonous energy should be especially prominent in midsized, open-canopied streams according to the River Continuum Concept. This is consistent with my past work on Goose Creek, VA (Vadas 1990). Besides this spatial pattern, there is a temporal trend. Allochthonous production is most important in the cold (fall/winter) season via leaf fall (for aquatic invertebrates) and terrestrial invertebrates (for drift-feeding fishes like salmonids, as emergence of aquatic insects is limited then).
-Bob Vadas, Jr.
Vadas, R.L. Jr. 1990. The importance of omnivory and predator regulation of prey in freshwater fish assemblages of North America. Environmental Biology of Fishes 27: 285-302 (cf. http://springerlink.com/content/r532l217v0816611).
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I'm working on a study looking at scale-dependent properties and drivers of food web stability in well-resolved food webs and am assembling a large compilation of food webs. I already have many webs, open databases of previous webs, as well as webs I've assembled, however more is better in this case. Does anyone have any webs (in any form) that they wouldn't mind sharing to be a part of the study? If used, your webs will be fully cited.
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Yes, are you interested in simple connectance data, or do you require additional information, or functional webs? Here is a link to a set of high resolution coral reef webs which we compiled for the Greater Antilles.
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Energy transfer between trophic levels is generally considered as equal to 10% of the net production at the preceding trophic level (the Ten percent law) => this law is used in numerous models, and I thought its origin was from Lindeman 1942, but is it not the case. Do you know what is the origin of this law ?
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Dont know its origin. And I dont think anyone should consider it a "law". It is a reasonable average for free=living consumers. Christensen and Pauly 1992 summarize many studies with a fairly wide range of valuesfrom a few % to the 20s %. BTW, the few studies on parasites/parasitoids indicate much higher values, up to 70%.
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It is generally accepted that plant-pollinator webs are nested and that nestedness promotes species richness in those networks. I've just read a study of Kondoh et al. ("Food webs are built up with nested subwebs", 2010, Ecology) stating that trophic interaction networks are nested as well, but with the inverse consequences, that is nestedness prevents species coexistence. I am studying host-parasitoid networks and I am wondering if in those networks nestedness would promote or impair species richness. I would be very interested to have your opinions.
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Yes. Maybe there has been a problem of formulation too. Some studies advocate that netedness promotes species coexistence. But it is certainly as you say other factors that govern the presence of species within networks and nested structure arises as a consequence, not as a cause. Maybe then there is also no sense to try relating nestedness to network robustness.
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A debated question in food-web research is whether omnivory stabilizes or destabilizes species interaction networks. Parasitoids often "consume" species from different trophic levels and their position in food webs is ill-defined. Therefore I would be interested to know whether you think that parasitoids could be considered omnivorous.
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Dear all,
Thank you very much! No problem with off-topics, it is really interesting and highlight the complexity of considering the place of parasitoids in the ecological communities. What I find really exciting is that through its different stages and host range, a single parasitoid can couple many different trophic levels. Instead of having energy flowing from one trophic level to the other (classical food chain), we have energy from several trophic levels flowing to a single parasitoid species. However, this is not restricted to parasitoids. For example, predatory wasps also need nectar as an adult and hunt prey for their larvae. Anyway, it is a real challenge to assess every possible interactions and processes that might influence the diversity and structure of an ecological community!
Best,
Valerie
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I am studying host-parasitoid interaction networks and I computed different indices that are common in food web studies such as linkage density, connectance, generality, orinteraction diversity. It is however well known that those indices are sensitive to the dimension of the network and that we should control for any effect of food-web size before making interpetation of the indices. My problem is what to consider as a measure of network dimension. I find different approaches in the papers I read. Some consider the addition of predator+prey species; some take a multiplicative measure: predator*prey species and still others enter the number of predator and prey species separately. What is your opinion on the most supported approach?
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I just read Dormann et al. (The Open Ecology Journal, 2009, 2, 7-24) and they report that 78 % of the variance in bipartite network indices was due to the number of higher trophic level species, which therefore represent the fundamental factor of influence on network properties. My point of view is that the influence of network size on the comparison between different networks depends on the magnitude of the difference in the dimension of the networks being compared. I would be happy to have your opinion about this.
Best,
Valérie
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I'm not very experienced with looking for information on R packages. If someone could help it would be great.
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If I understand correctly, a Lindeman spine is just a series of flow networks, so I'd start with the "enaR" (tools for ecological network analysis) or maybe go as primitive as the "networks" (relational data) package. Either of these should allow you to design and implement flow networks. Maybe even try the "foodwebs" package.. but I have no experience with it so maybe someone else can chime in...
Just suggestions. Hope they help!
Package links:
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I would like to improve some old ecopath models that have no bacteria compartments in estuaries where we lack information about bacterial production. I would be interested in your advise about using other data related to microbial activity like enzymatic activity or metabolic rates in order to seek for good data sets.
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If you are interested we have a set of data on microbial metabolic rates, see Puddu et al. Hydrobiologia 1997 , Zoppini et al Sc Tot Environ 2005, Pettine et al Est. Coast.Shelf Sc, 2001) and more recent data still unpublished on the Adriatic Sea and Cilician basin (Turkey)
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I have data on quantitative food webs from different sites over three years and three different isolation levels (10 sites for each isolation level). The idea was to look at spatial-temporal changes in the food-web structure; however, the food webs from each site considered individually in each year are very small and do not give reliable results.
I have two alternatives: either pool the data from the three years together for each site and look for the spatial pattern only, or pool the data over the different isolation levels for each year. Both methods are critical as they do not take into account variability either in time or in space. I am be very interested to have your opinion about which approach could be more appropriate. Thank you very much
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Yes, but sorry, I did it in Indonesian language.