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I am currently studying the interaction of Twitter memes (two or many), such as competition and cooperation. Is there any model or method in biology that can identify the types of the relationship, such as competition or cooperation?

I have heard the Lotka–Volterra equations, but when I begin to dig deep, I found that it is still not suitable.

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  • $\begingroup$ Welcome to Biology.SE. By identify, are you referring to methodologies of identification of to definition. In other words, are you asking for comonly accepted definitions or for methodologies to detect a concept that you have already defined (in which case, can you please your definitions). $\endgroup$ – Remi.b Nov 5 '15 at 2:39
  • $\begingroup$ @Remi.b Yes. I want to know the commonly accepted/acknowledged methods to define competition and cooperation between specifies. $\endgroup$ – Shuai Zhang Nov 5 '15 at 2:43
  • $\begingroup$ I am not sure what you mean by "methods to define". Either just "definition" or "methods to detect"would make more sense to me. I wrote an answer to provide some info about the definitions of the different biological interactions (and not about the methods to detect them). $\endgroup$ – Remi.b Nov 5 '15 at 2:55
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Species interactions

Generalities

Species interact. Species actually interact a lot. One can classify species interactions into categories based on the effect that the interaction has on their fitness (≈ reproductive success). Here is a table of possible biological interactions (comes from [wiki][1]), where a + indicates "beneficial", a - indicates "detrimental" and a 0 indicates it has no effect on fitness.

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Different terms exist for a given relationship. Typically, antagonism is often called parasitism.

Note about symbiosis

Different authors use the word symbiosis differently. From wikipedia:

The definition of symbiosis is controversial among scientists. Some believe symbiosis should only refer to persistent mutualisms, while others believe it should apply to any type of persistent biological interaction (i.e. mutualistic, commensalistic, or parasitic).[6] After 130+ years of debate,[7] current biology and ecology textbooks now use the latter "de Bary" definition or an even broader definition (i.e. symbiosis = all species interactions), with the restrictive definition no longer used (i.e. symbiosis = mutualism)

Blurry limits

Generalities

It may seem pretty obvious that two species should have either one type or another type of interaction. However, the reality is often more complicated than that. An interaction might fall in one category under one set of environmental conditions and fall under another category under another set of environmental conditions. In addition to that, it is not uncommon that due to selection on the host genes due to the presence of a parasite, the host evolve so to tolerate the presence of the parasite up to the point of actually having a lower fitness in the absence of the parasite.

Example of environment-dependent interaction type

Consider an animal that is host to an algea. The host is providing shelter to the algea while the algea is providing sugar (produced through photosynthesis). If there is no light or if the enviroment is loaded with sugar, then the host has no gain of hosting the algea. In such case, the algea may even be parasitic. If, however, there plenty of light and there is few nutrients in the environment, then the algea and the host have a mutualist relationship.

Example of the evolution of a parasitic interaction

Consider for example a snail which is infected by a parasite. Let's assume (I think it is a real world example but I am too lazy to find out a reference) that the parasite need the snail to be eaten in order to reproduce in the body of the predator. In order to improve the chance of its host to be eaten the parasite is selected so to diminish the thickness of the snail's shell. In response to that, there is selection (which intensity depend also on the proportion of infected snails in the population) for having thicker shells. But now, snails that are not infected have shells that are so thick that the can't move as fast as they'd need to forage. So, by the end infected snails may have a higher fitness than non-infected snails. And therefore the interaction between the snail and its parasite is not a parasitic interaction anymore but a mutualistic interaction.

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  • $\begingroup$ Is there a mathematical model or analysis that can determine the types of interaction based on the specifies' population growth curve? $\endgroup$ – Shuai Zhang Nov 5 '15 at 3:04
  • $\begingroup$ Not that I am aware of. You might want to ask further questions on CrossValidated.SE and eventually use dummy data and ask how can one investigate this question knowing that there is a delay between the change in size of one population and its affect on the other population. $\endgroup$ – Remi.b Nov 5 '15 at 22:10

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