Dear Haines, We do not seem to be getting much clearer. I guess it would help to know what the philosophical import of your questions might be? 

In my comment on the possibility of behaviour altering DNA, I was just referring to altering the base sequence. My point was that I could almost certainly alter the sequence of my germ cell DNA in a laboratory in a way that would vaguely approximate to what people think of as Lamarckian and there are probably other examples in bacteria or viruses that vaguely approximate in some other way but it is way outside reasonable plausibility that these are relevant to the evolution of vertebrate behaviour on a wide front. When I referred to AID I was meaning activation induced deaminase, as in my previous post, not the AIDS virus. Sorry for not being clear.

In the case of the wasps I think it is very likely that longer nests would have an effect on niche. The length might affect how often nests were blown down on southwest facing slopes or how easy it was for honey buzzards to break off chunks to carry away. If half a colony of wasps were building long and half short the nest might easily end up useless, whereas separate pure colonies would make good nests. 'Adaptive functionality' is a hugely complex phenomenon.
 
Maybe what you are getting at in the small bird example is an interesting point that struck me when visiting the Galapagos Islands (no, really, it did). It is another example of how Darwin was actually wrong about many things but deserves the credit for getting the basic idea of evolution by mutation and speciation right. (There is no suggestion that his mistakes merit a return to Lamarck.) The famous finches of Glalpagos come in about nine species - large, medium and small ground, woodpecker, vegetarian, warbler, tree etc. It is quite likely that all these birds derive from a single pair of mainland finches that got blown to Galapagos in the same storm by a freak chance. (There are only about thirty species of small non-seabird on the islands, indicating just how rarely pairs of birds of the same species arrived in the same lifetime.) If, as it seems, conditions were favourable, the pair would have had hundreds of offspring. These would have spread sparsely around the islands. Because there is normally significant allelic variation in genes for physical phenotypic traits (it may have the advantage that individuals can be recognised) the offspring will have varied a bit. Those with slightly fatter beaks would tend to congregate in areas with seeds that are very nutritious but hard to open. Those with thinner beaks would tend to congregate where there were more bark inhabiting insects that were hard to tweak out. As soon as these congregations started to interbreed locally there would be a major enhancement in the difference between groups. If there are ten genes that contribute to beak thickness, which in an outbred population are randomly mixed to give an average beak, preferential interbreeding of birds with e.g. fatter beaks (because of territory) will rapidly lead to a group with all ten genes being of the pro-fatter alleles. This may be quite enough for them to look like a new species. No natural selection in the sense of variable survival needs to be suggested. All the birds at this stage can survive. However, in order for true speciation to occur the macro-formatting of the birds' DNA must drift enough for them to become back-cross infertile. This will happen naturally by DNA structural drift (again no survival pressure) as long as the groups live in different places and have the behavioural trait of sticking to their patch. Once speciation has occurred a new force will come in. Birds with DNA that encodes the behaviour of 'chasing girls with the same size beak as you' will procreate better than birds who chase any old girl and at territorial overlaps too often pair up with a genetically incompatible mate. So from this point on mutations in behaviour encoding genes will be selected for on a survival of offspring basis (not survival of individual).

But to come back to your point "To argue these differences are there because of a subtle adaptive advantage seems a stretch. More likely, it seems a genetically encoded habitus." I am not sure why you see these as alternatives rather than both true. In conventional theory both are true. Except that differences are not there because of adaptive advantage in the sense that their existence is due to adaptive advantage. Their existence is due to mutation and their persistence is due to adaptive advantage. Feathers did not evolve because they were good for flying. They evolved by mutation and then continued because they were good for flying. Successful speciation is dependent on the random occurrence of mutations that ensure new behaviour patterns that tend to ensure selective interbreeding within a group with the same DNA macro-format (by that I mean things like the number of chromosomes the DNA is split up into).
Best
Jo