miércoles, mayo 28, 2008

Parental Care Usurpation as a model for thinking about Developmental Systems

Parental Care usurpators exploit the social behavior of their hosts, this “modo de vida,” it is present in numerous taxa and involve the partial sequestration of the ontogenetic niche of the host species. In this commentary I will mention two cases of parental care usurpation: the avian brood parasites (e.g. cuckoos) and the ant nest usurpations (often called slave-maker ants or pirate ants).
Due to the very emergent properties involved in the evolution of these life styles; these cases are interesting models for thinking about the value of Developmental System Theory or Evolution by Means of Natural Drift as explanatory backgrounds.

Previously in this blog, we have seen comments about the relevance of the “incomplete isolation” of the multicellulars systems processes as a way to understand certain kinds of dynamic changes in the ontogenetic niche. This “epigenetic permeability”, could be suggested as a property that may help to understand why it is not always necessarily an “Internalization” (i.e incorporation of adaptative traits in the genome of the evolving species) for the development of new life styles or lineage changes in order to get an idea of the points when this “epigenetic permeability” may help to explain the establishment and conservation of these life styles, lets compare the steps of the parasite-host interactions.

In avian brood parasites, the female lays the egg in the host nest, which has been recognized by some authors as the only interaction between the parasite and host species. I would suggest to add a second step that is performed by the parasite chick: the expulsion from the nest of the host offspring (this does not always happen though). For the realization of step one of the interaction, the parasite mother had to find the appropriate host nest and the host parents have to be fooled to keep believing that the extra egg belongs to them. Some parasites species present similar egg pigmentation with their main host, but it is not clear, as far as I´ve read, that this is genetically determined and that this trait can vary inter and intraspecies. The second step is very similar to other kind of parasitic interaction where the allocation of resources is diverted to feed the growing parasite (See Sacculina barnacles post in this blog as an example).
In ant nest usurpation species, the first step involves the usurpation of the queen host throne by the parasite ant. The female searching for nest, sneaking in the nest without being detected as alien by the colony, and (as similar as the avian parasite chick) the diversion towards the reproducing parasite.
In the second step, the parasite queen offspring will search for new host colonies, raid them and kidnap host worker’s larvae. Experiments have demonstrated that when two alternative host are available for the queen and she picks one of them in the first step, the parasite sons will also choose that one for collecting more workers.

This two examples suggest to me that the Developmental System is more than the niche variables and the inheritable organism material, and cannot be reduced to the somatic and germinal part as a satisfactory explanatory background but also the construction of these parasitic life styles due to epigenetic permeability are possible thanks to crucial behavioral operations (“conducta” in Maturana’s approach) that allow the emergence of these very externalized and dependent systems.



Cristian Villagra

10 comentarios:

Sanders dijo...

"Experiments have demonstrated that when two alternative host are available for the queen and she picks one of them in the first step, the parasite sons will also choose that one for collecting more workers"

Esto es interesante porque muestra aspectos de aprendizaje y conductuales que combinados repiten una asociación particular (que podría haber sido otra). Es una forma de "internalización" sin siquiera físicamnete internalizar la reproducción del simbionte.

Esto puede ser un ejemplo de herencia "distribuida" o cíclica mediada por aprendizaje en el "ciclo de vida" de un hormiguero esclavista, no tan distinto a lo que ocurre con el "legado químico" en parasitoides o el salmón que siempre vuelve a su río de nacimiento

en efecto todo el fenómeno de la hormiga esclavista no sería posible si la reina esclavista no fuera capaz de hacerse pasar por la reina usurpada, y en efecto creo que leí por ahí que la reina invasora lleva incialmente una impronta química de la especie invadida...pero no recuerdo cómo...

Sanders dijo...
Este comentario ha sido eliminado por el autor.
Sanders dijo...

"The new queen mimics the old queen by consuming pheromones from her body and releasing them to the attending ants"

He ahí la afortunada coincidencia.

(Un "overlap"!)

Cristian dijo...

Es interesenta pensar en el valor que tienen los procesos conductuales en interacciones de dependencia que se mantienen evolutivamente,

Por ejemplo, otro caso interesante es el de la Yucca y l a polilla de la yucca, en algunas especies para que ocurre polinizacion es ESTRICTAMENTE necesario que la polilla trasporte activamente el polen de la flor al estigma, junto con transportar el polen la polilla oviposita en el fruto fecundado. Como consecuencia las larvas de la polilla consumen PARTE de las semillas
en su crecimiento, mientras el resto de las semillas
puede constituir la siguiente generacion de Yuccas..
o sea si el comportamiento de traslado de polen de la polilla no ocurre tanto el sistema planta como el parasito-polinizador no pueden construirse nuevamente...

Nucleo Decenio dijo...

Bueno, y respecto al valor de los procesos conductuales como propiedades emergentes en los cambios ontofilogeneticos....

Speciation by perception

Anders Brodin and Fredrik Haas

During sympatric and parapatric speciation the diverging populations maintain geographical contact throughout the speciation process. In theoretical models an isolating mechanism, such as assortative mating, is usually needed to obtain genetic separation of populations in contact. We simplified the visual appearance of the crows that occur in the crow hybrid zone in Europe, the carrion crow, Corvus corone, hooded crow, C. cornix, and hybrid crows. We then mimicked the sexual imprinting process by training artificial neural networks to separate their own type from the other two. The network learned pure phenotypes faster and better than the hybrid patterns showing that already at the receptor level there may be signal reception properties that will make speciation under sympatric and parapatric conditions possible. Thus, mate choice preference can be a self-emerging nervous system property not requiring evolutionary selection.

Animal Behaviour
Volume 72, Issue 1, July 2006, Pages 139-146

Sanders dijo...
Este comentario ha sido eliminado por el autor.
Sanders dijo...

Está demosstrado experimentalmente que los polluelos luego prefieren parejas con rasgos y canto parecido a los papás. Una deriva cultural del canto o un polimorfimso de las plumas pueden terminar en especiación.

El experimento de la red neural me parece que tiene que ver con cómo a mayor "distancia morfológica", es más fácil diferenciar dos objectos

Cristian dijo...

Seria interesante hacer un metanalisis para cachar n cuantos de los casos de asociaciones estrechas (parasitos usurpadores de nichos, parasitoide, eusociedades, etc) la relación presenta al menos un paso significativo que involucre un proceso conductual...

cristian G. dijo...

interesante tema, en un paper que encontre el ano pasado sobre evolucion de parasitismo en pajaros, el autor revisa las "pre-adaptaciones" presentes en casa clado que permiten el parasitismo. un punto en comun a todas las especies parasitas es venir de especies donde la hembra no construye un nido . las historias que llevan a esto son partuculares de cada clado , pero tienen en comun una conducta que permite ser parasito.
aqui les mando el paper, la parte de las preadaptaciones es interesante el resto se pone medio latero con las ventajas adaptativas de ser parasito.

http://www.zshare.net/download/13007714cdf060ea/


chinaksy

Anónimo dijo...

Vale friend, gracias por el paper!

que gueno el dato de la perdida del nido!,

Cuando te tinque tirate con un post pal Decenio

Saluti!


Diablete