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quarta-feira, 9 de julho de 2014

Using feline behavior to test a method to reconstruct phylogeny (or how to be paid for spending endless time observing wild felids)

Since very early in my childhood I am absolutely fascinated by felids, from the domestic cat to the lion, from the tiger to the black footed cat. And as my father asked, even in those early days, what I would choose for a job, I always wondered how I could get paid for just being around cats, the wild and the domestic ones. Well, I succeed. As a Professor at Unesp, one of my most important “duties” is to watch feline behavior. I already enjoyed different kinds of scientific work with these wonderful animals. I searched for their foot prints and other vestiges while tried to see them in the wild. I observed them in zoos throughout my country and abroad, while videotaping them in order to see it later again and again and so being able to understand what I was seeing. I chased domestic ones in the nights of my small town to figure out what would they do when outside our homes. I analyzed color, shape and size of their hairs to build a key to tell between the Brazilian species when only small pieces of fur or individual hairs are available. I even looked for DNA in those hairs.
In one of those works observing felids in zoos, I came to the idea to use behavior as character to reconstruct phylogeny. Studying phylogeny is to try to understand how species are related to each other. As an example among rodents, it could be said that the mouse is more close related to the rat than to the shrew. To reach such a conclusion, one might compare bones, mostly the ones in the skull, or the DNA of the in-group, the group of species one is interested in reconstruct its genealogic tree, its phylogeny. Characters based in skull bones or DNA are the most common ones. But proteins, ecology, soft parts morphology and other can be used as well. Behavior is not so a common source of characters because of out of date opinions shared by ancient scientists. But this is turning and the use of behavior as character source for phylogeny is becoming more and more usual.
In that particular research, I observed adult domestic cats (Felis catus), that lived in colonies of, at least, four individuals. I used data collected mainly in two colonies. The cats didn't belong to any particular race, being just avoided the black cats, or very dark ones, because of difficulties to visualize behavior. There was not gender distinction when choosing the individuals.
The other feline species included in that work were the Bengal cat (Felis bengalensis), the Caracal lynx (Linx caracal), the Serval (F. serval), the Asian Golden Cat (F. temmincki) the Geoffroy's cat (F. geoffroyi) and the Onsila (F. tigrina). The nomenclature of felids followed in that work is the one indicated by Gittleman’s Carnivore Bahaviour, Ecology and Evolution, from 1989. The data were collected in videotapes done, mainly, in four institutions: Fundação Parque Zoológico de São Paulo, Brazil; Zoologischer Garten Berlin and Tierpark Berlin-Friedrichsfelde, both placed in Berlin and Zoologischer Garten der Stadt Wuppertal, in Wuppertal, Nordrein-Westfallen, Germany. I also have done some filming in the Zoos of Sorocaba, Brazil, and the one of Copenhagen, Denmark.
I choose to use facial grooming as the source of behavior suited to phylogenetic analysis. Considering both sides of the face, felids display no less then forty five different grooming behavioral units, including parts of the anatomy like the face itself, the tongue and the forearm (for the feline grooms its face with the front paw after it have been licked by the tongue). These are some examples of these behavioral units:

PLB - Protraction of the tongue, down. 
The animal opens the mouth, protracts the tongue up to about 1/3 of its maximum extension and, then, curves it down. 

ZAB - Forearm.  
After PLB, with the paw lifted up, with the palm turned to the internal side, the cat moves the head in direction to the chest, touches the tongue in the base of the forearm, moves the head frontward and the paw backwards, licking the forearm along and, than, retracts the tongue

            ZPH - Paw to eyes 
Departing from ZAB, without touching in the face with the paw, with movements of the head and the arm, the paw goes by the superior lip, by the vibrissae and by the eye until landing in the forehead area.

ZHV - Eye to vibrissae 
Departing from ZPH, the paw touches the face and goes down, with movements of the arm and of the head until the forearm reaches the superior position of insertion of the vibrissae.

PLB, ZAB, ZPV and ZHV are part of the mnemonic codes I used in that work.  I got 29 ones, for I didn’t discriminate between left and right sides of the face. All observed felid species display them. And as all species showed the same grooming movements, it wasn’t possible to use them to compare species. To do so, I studied in what sequence each species used the different behaviors to clean its face. It’s important to say that it’s not usual at all to use sequences in behavioral studies. Most scientists use the frequency that the animal displays each behavioral unit. This means that most scientists count how many times each behavior is showed by the animal subject in a given amount of time. But to use sequences is preferable because they are much less altered by the environment then frequencies do. And different species showed different sequences in the facial grooming while sticking to the same pattern among the different individuals of the same species. So, using sequences is a kind of a little breakthrough of my work. To extract sequences from the raw data, the behaviors observed in the videotapes taken in zoos, is not so straightforward and thus, me and my collaborators build a software based in a mathematic algorithm created by one of us, the MrDiTree algorithm.
So, as the characters used to reconstruct the phylogeny of the species studied being the sequences of grooming behavioral units, I had the way compare them. And each species had more sequences in common to another one then to the others. I summed up all the sequences each one species shared with every one other and so, using a dedicated computer program, I could tell the distance of relatedness, the phylogeny, of the studied species. The result is the figure below:

It is a cladogram, a graphic outline used to show a reconstructed phylogeny. What the cladogram tells is that, among the observed species, the Caracal is closer related to Geoffroy’s cat than to any other species in that work. They are sister species. The same can be said from the domestic cat and the Bengal Cat. In this phylogenetic tree, the Asian Golden Cat is closer to the clade that bonds Bengal and Domestic Cats. And the Serval is closer to the former group. Onsila is isolated from any other species or group of species, meaning that it is farther linked to the others.
Comparing these results to Felid phylogenies proposed by other authors it can be seen that part of this cladogram is not so diverse whereas other part is so. The worst part is that Geoffroy and Tigrina are not together, since they are South and Central American species and it is hard to believe that they do not share the same evolutional step that lead to creation of the South and Central American spotted cats group. One possible explanation for that result is that the Onsila individuals I used in that work were from very different origins and I think that at least some of them were hybrids between Onsilas and other felid species. If I’m right in this, of course all grooming behavior sequences certainly wouldn’t be that of pure Onsilas.
Well, this only a brief summary of that work of mine. The whole story can be read at Japyassú HF, Alberts CC, Izar P, and Sato T (2006) EthoSeq: a tool for phylogenetic analysis and data mining in behavioral sequences.  Behavioral Research Methods 38:549-556.
I am now interested in the evolution of social behavior among the Felidae. Like others, I believe that the cat is not the only species of that Family that is apt for domestication. I think that many other feline species would be domesticated if the same circumstances that lead to the domestication of the cat had arisen to them too.
So I am proposing a questionnaire to the members of zoos in Brazil as well around the World. In this survey I am asking about some particular behaviors felids maintained by members may or may not display towards its owner or handler. Some other information is also asked for. I will then be able to compare the results with those of other similar surveys, done in a bit different research design were the closer human/feline bond showed by zoo keepers members and their wild cats wasn’t taken in account. 

Responsável pelo texto:  
Dr. Carlos Camargo Alberts
 (Professor Assistente Doutor do Departamento de Ciências Biológicas da FCL, Assis – UNESP