Can Domestic Selection cause Macroevolution?

I don't think that this distinction is meaningful. The "environment" that places NS pressures on a population includes all biotic and abiotic factors that it interacts with, and this certainly includes humans and human activities."Fitness" doesn't necessarily refer to the physiological robustness, but rather to reproductive success. From this perspective, an excellent "strategy" for increasing overall fitness is to enter into a symbiotic relationship with humans via agriculture. This type of selection is not even unique to humans; similar interactions occur with insects (ants, termites, ambrosia beetles) that practice fungus agriculture, for example.

I'm very confused as to what your point is here. Could you clarify? At all times both ants and fungus are subject to selective pressures, both from each other and from other environmental factors. The same is true of humans and our agricultural species. Symbiosis does not necessarily mean that each species can't live without the other. That's a particular kind, known as "obligate" symbiosis (specifically, obligate mutualism). Symbiosis can also be "facultative," meaning that the interaction can be beneficial to one or both species, but is not necessary for survival. In the case of a crop that is no longer able to effectively survive without human interation, it would be obligate for the crop and facultative for the human. We still do have the wild apples in their native range (and in introduced ranges, too). The same is true of most commercial crop plants; their wild ancestor populations are still extant (there may be exceptions, although I can't think of any). Those populations which have a mutually beneficial relationship with humans, and are cultivated, tend to have greatly increased range and prevalence. Meanwhile, new genotypes continually emerge as they do in nature, and some of them in turn may also be cultivated.Actually, apples (and pears) do not "breed true" in terms of their fruit qualities, and the commerial varieties we have are ones that were discovered by lucky chance after essentially random reproduction, and now must be propagated through cuttings and grafts. The Malus species show remarkable plasticity. I repeat, the varieties we eat were not selectively bred, and their offspring do not tend to be very similar to the parent trees. An excellent and very readable book that explores these and related topics is The Botany of Desire, by Michael Pollan.This message has been edited by Belfry, 04-04-2006 07:00 PM

You are assuming, oddly, that humans will disappear suddenly (when you state that maize has committed suicide by depending on us). Thus far, we humans have been VERY beneficial to that lineage. It has gone from a Mexican annual grass of relatively limited range, to a plant with huge diversity and worldwide distribution.It's like saying that the an Ophiostomoid fungi that a species of ambrosia beetle cultivates "committed suicide" by relying exclusively on the ambrosia beetle for transportation and innoculation into new host trees. Sure, if all beetles of that species mysteriously disappear, then the fungus is screwed. What does that have to do with the fitness of the fungus right now?ETA: For that matter, you could say the same thing about any obligate parasite (one which requires a host for survival and/or reproduction). Have they "committed suicide" by developing reliance on a host?This message has been edited by Belfry, 04-04-2006 10:56 PM

This is nonsensical. What does "picking a path" have to do with the discussion? Everything dies, the issue in this case is reproduction. Domesticated maize now requires us for part of its life cycle, just like in any other obligate symbiosis (from mutualism to parasitism). One way of looking at it is that domesticated maize is well-adapted to exploit humans as a highly efficient dispersal agent. As I have pointed out, it has proven to be a very effective strategy for this lineage.This is not at all unusual. Flowering plants have developed structures allowing them to exploit insects and other animals for pollination, and specialized fruit to employ animal seed dispersers. Their animal counterparts have also adapted to better benefit from the relationship. This is coevolution in a nutshell. I have demonstrated that both humans and maize, as species, benefit from their interaction in the same way that other well-documented symbiotic organisms do in nature (such as ambrosia beetles and their fungi). If you think you can refute this, please do so. Your comment about parasitism is a non sequitur, as far as I can tell. Well, disappear from the interaction, anyway - same issue and same problems with your statement.This message has been edited by Belfry, 04-05-2006 08:41 PM

Conscious intent is immaterial, though it may make the process more efficient. The process in non-human examples is much the same as in human agriculture; crops which are more beneficial to the cultivator (be it human or insect) are selected for, deleterious phenotypes are selected against. Not until we developed more direct genetic manipulation techniques (gene insertion and such) did human methods fundamentally differ from this process. This is essentially correct... it's not necessarily goal-oriented, but even if evolution is guided by humans, with humans as the primary NS agent and with a human goal in mind, it's still evolution. Well, I think it is arguable whether the Native Americans foresaw what would result when they started to cultivate that native annual grass, or whether they just preferentially cultivated varieties that arose on their own.In any case, I agree that human consciousness and forethought are unique in contributing to these interactions. However, "domestic selection" still isn't a fundamentally a different process from natural selection. The more beneficial plants are still selected as more "fit," it's just that human perception is the primary determinant of fitness in that case.

If the crop or animal produce a better yield, then we will encourage their reproduction, meaning that they are more "fit." If an ambrosia beetle's fungus is more nutritious, it will increase the beetle's ability to reproduce and it will be cultivated more. It's still the same thing.

A crashfrog said and WK elucidated, symbiosis just means that the relationship exists; the type of relationship (and its relative effect on each organism) is further described as mutualism, commensalism, amensalism, or parasitism. In popular usage, symbiosis=mutualism, but biologists use the term more broadly, because the relationships don't always fall into neat, set categories.In fact, a mutualistic relationship can even become parasitic, depending on other factors. For example, take the well-known mutualism between nitrogen-fixing Rhizobium bacteria in legume roots. In environments with low available soil nitrogen, the relationship is beneficial to both the host plant (which benefits from the atmospheric nitrogen fixed by the bacterium), and the bacterium (which receives carbohydrates from the plant). If the plant is grown in an environment with high available soil nitrogen, the bacterium becomes unnecessary, and the plant loses carbohydrates to the bacterium without any gain for itself. The bacterium is now a parasite. Thus legumes grown in high-N environments often have fewer (if any) root nodules.This message has been edited by Belfry, 04-06-2006 06:48 AM{edit: spelling errors}This message has been edited by Belfry, 04-06-2006 11:05 PM

No, not as biologists use the term. As I said before, what you're describing would be called an "obligate mutualism." This is a type of symbiosis, as are parasitism, amensalism, and commensalism.

I agree, crash, you've used the terms both consistently and correctly throughout, as far as I can tell. This confusion is bizarre.Since most of us, including kuresu, seem to agree that symbiosis includes many types of relationships, including both parasitism and mutualism, and may be obligate or facultative... perhaps we can move on at this point.

Well, I'm an ecologist, too - maybe it's a generational difference? The way I learned it, these things run along a continuum. Parasitism is not a mutualism - never said that - but a relationship can turn from mutualistic to parasitic depending on environment, such as with the Rhizobium/legume example I gave earlier (and I could give other examples, both plant and insect).Also, it doesn't have to be "highly negative" to be parasitic - just negative. There are gradients. Again, this is the way I was inculcated, less than a decade ago, so maybe it's just a matter of changing usage.This message has been edited by Belfry, 04-07-2006 10:16 AM

Really, a cerambycid? Sounds interesting, I'll have to look it up.Sounds like we have some things in common... I work with forest insect pests. And I'm a cyclist, too .