resources on species selection

April 4, 2011 12:26 PM

What traits can a group of organisms possess that an individual cannot possess (e.g. a ratio of males to females)? To put it more generally: in reference to units of selection, can you cite any examples of a whole being greater than the sum of its parts (particularly the sum of its genes)?

I am researching species selection. I would appreciate any good essays, books, articles, etc on this topic. I'm currently reading a relevant chapter from Gould's Structure of Evolutionary Theory, but Gould is incredibly long-winded and I have a deadline to meet.

posted by Vic Morrow's Personal Vietnam to science & nature (8 answers total)

Well, kin selection makes no sense except within the context of a group. And lots has been written on it.

Division of tasks within an ant colony is a group trait, for example, and driven by kin selection.
posted by vacapinta at 12:30 PM on April 4, 2011

Bacteria work together! For instance, they can do things like sense how many are in their population and then when they have enough numbers to do Action-X they will all work in unison.

Here's an article about how we're hoping to use that to better treat diseases.

And we think that multicelled organisms came from a colonies of single-celled organisms working together.
posted by Wink Ricketts at 1:04 PM on April 4, 2011

altruism?
posted by yeahyeahyeahwhoo at 1:17 PM on April 4, 2011

Insect that have colonies? like ants and bees. As individuals this organism can't really survive for long, but as a member of a colony they are quite robust. I think what you are asking for is emergent behavior. That a large enough group of things will display a behaviour that no single isolated individual will display. Humans display it with cities and economies (although probably outside the scope of what you want to tackle on this).
posted by bartonlong at 1:26 PM on April 4, 2011 [1 favorite]

You may want to look up endosymbiotic theory if you're doing this based on the 'sum of it's genes' and want to address the issue on a fundamental level. I'm thinking like when chloroplasts and mitochondria became a part of the community inside a plant and animal cell. Bacteria inheriting plasmids is another example.
posted by surfgator at 2:00 PM on April 4, 2011

E. O. Wilson (of all people!) and a couple of colleagues have recently mounted a strong challenge to the kin selection model of the evolution of eusocial insects (such as ants that form colonies) and perhaps other animals such as naked mole-rats:

says Wilson, the Pellegrino University Professor, Emeritus, at Harvard. "We hope our new theory for the evolution of eusociality will open up sociobiology to new avenues of research by liberating the study of social evolution from mandatory adherence to kin selection theory. After four decades ruling the roost, it is time to recognize this theory's very limited prowess."
posted by jamjam at 3:08 PM on April 4, 2011 [1 favorite]

Versatility/Individual adaptability and Mobility:

Consider General Sheep, which can survive both in arctic and tropical climates without diverging into separate species, and populates both. Contrast this with Arctic Sheep and Tropical Sheep, which cannot inter-breed and populate only their respective territories. When an ice age strikes the arctic, both General Sheep and Arctic Sheep will be severely weakened or extinguished. As conditions improve after the disaster, General Sheep can re-supply its population from the tropics, whereas Tropical Sheep stays where it is and Arctic Sheep remains extinct or weak. Similarly, a draught may take its toll on all sheep in the tropics, but only General Sheep has a strong polulation to derive new members from.

The speices of General Sheep is the winner here, since it maintains a redundance when any one geographical zone becomes uninhabitable. This depends on population dynamics and geological/climate events on a time scale shorter than species adaptation, so it cannot be reduced to the individual level.

I'm not a biologist or anything, this is just what I thought up while some updates were installing. It seems to have worked well for us humans though.
posted by springload at 3:11 PM on April 4, 2011

Biofilms probably fit your description. When a bacterial colony reaches a certain size, governed by the quorum sensing mechanism of the colony, it begins to develop a complex community including multi-cellular structures, waste elimination and defensive measures. Makes for a nasty problem with catheters left in for too long. Memail me if you don't find enough references online; I might still have a few listed from an old graduate program. Good luck!
posted by sapere aude at 9:11 PM on April 4, 2011