Talk:Inbreeding depression

Untitled

I am taking this out of "needs to be cleaned up" because I think I've cleaned it up fairly well. 128.101.70.96 15:21, 21 October 2005 (UTC)lotusduck

Hybrid vigor?

To me this seems to be the opposite of hibrid vigor, but I am niave on this subject. If this is correct, probably worthadding to the article. ike9898 04:16, 8 October 2006 (UTC)

Not really - "hybrid vigour" is a function of increased levels of heterozygosity in a population. Inbreeding depression comes from an increased frequency of deleterious alleles in a small population or from increased homozygosity in recessive deleterious alleles. Guettarda 13:38, 20 November 2006 (UTC)

Possible Vandalism

"Residents of Vlotho, Germany". I am assuming good faith, since it is added with an other entry, but can someone confirm this? Asm82 17:14, 8 May 2007 (UTC)

I assumed bad faith, but more importantly, since it's not a wikilink, it's useless to users. Plus, they f'ed up the formatting with their addition, which smells like vandalism. Ergo, I removed it. If they really feel strongly about it, they can post it on the talk page. WLU 01:17, 9 May 2007 (UTC)

Taxonomic bias: This article seems to mostly be concerned with (vertebrate) animals

Which is unfortunate since ID seems rather ubiquitous and is especially important in the study of the evolution of plant mating system. (Most plants being hermaphrodite, often with male and female function placed in the same flower).

Taxa not suffering from ID ?

Hmm, looks like this is animals - most examples, anyway, that have gone through a severe bottleneck and survived. Isn't the usual way to investigate ID to produce some inbred and some outbred lines and compare their fitnesses? How, is one to do this in a species where there is only one line? Even though this line seems to do well it may not be in mutation-selection balance? Anyway, seems like this section takes up to much space in this article.

In humans?

Supposing an isolated population of humans, mostly cut off from civilization, became so inbred over several generations that the population was particularly subject to problems such as birth defects or mental retardation. Would this be considered a form of inbreeding depression? I know this has happened to some degree (as is the case with the Ulas family), so would this be an inbreeding depression or is there another term for it altogether when this phenomenon occurs in some form in a human population? Thomasiscool (talk) 20:39, 4 July 2008 (UTC)

OK, I have found one reference within that ostensibly refers to this occuring in humans; the article on the Vadoma (the two-toed people of Zimbabwe) says that "the Vadoma are a popular example of the genetic effects of small population size on genetic defects and mutation. Due to the Vadoma tribe's isolation, they have developed and maintained ectrodactyly, and due to the comparatively small gene pool, the condition is much more frequent than elsewhere." Subsequently, the article about small population size has an entire section about the genetic consequences of dangerously low populations. It had never occurred to me to look here, but this seems to refer to exactly what I was asking about. Still, though, I am wondering a) to what degree this does occur in human populations, and b) should we make reference to the genetic consequences of small population size in this article? Please give your thoughts on this. Thomasiscool (talk) 20:50, 4 July 2008 (UTC)

I don't know the answer to (a) but if you want to add (as per b) to the article just be bold and do it. If other editors disagree then they change/revert whatever. I do have a comment to make about this article however. In the lead it states, "Breeding between closely related individuals, called inbreeding, results in more recessive deleterious traits manifesting themselves." My problem with that is the assumption being made that all "deleterious traits" are recessive. There is even a whole article that seems to be supporting that stance? My view is that deleterious traits/genes can also be dominant. Well I should include co-dominant or partial dominants here also. A partial dominant being expressed differently phenotypically in the homozygous state than it is in the heterozygous state. There are many examples of lethal or partial lethal genes that are actually dominants rather than recessives to wildtype. Anyhow I'm waffling on but my main point is that the comment that inbreeding results in more "recessive" deleterious traits seems to imply (unless I'm reading it wrong?) that only recessives are bad? What do others think about this?--Sting Buzz Me... 23:40, 4 July 2008 (UTC)

Hmm, I'm no expert on the specifics of genetics, but thanks for answering my original question. I have devoted an entire section to the occurrence of this problem in humans, including real-life examples. However, I have a very limited knowledge of such cases, and in any event, my best guess would be that many of them are, if not completely unknown, not widely known. If anybody knows of any more cases involving some form of inbreeding depression in humans, please do not hesitate to add them. BTW, does anybody else agree that this whole issue seems to relate very closely to the shaky concept of backward evolution? Thomasiscool (talk) 00:29, 5 July 2008 (UTC)

The idea of backwards or forwards is wrong in that Evolution is not about a "direction". As I understand it Evolution is pretty much a species surviving via natural selection to "fit" the niche that it is in. So "how" it evolves depends on survival of the fittest (adaptions/mutations) to the environment it is in. How this subject relates to backward evolution I'm really not sure?--Sting Buzz Me... 00:54, 5 July 2008 (UTC)

I agree, and this is why I referred to "backward" evolution as a shaky concept. In my own opinion, there has to be a better term to encompass what this concept means. The reason I think the two topics are related is because it seems to me that in many cases the inbreeding depression could cause a high enough prevailence of one or more deleterious traits that it would cause the population to become so much less fit than average that they at least seem to revert to more primitive ways. The example that comes to my mind is the Ulas family (not sure if you're familiar with them?). Anyway, their unique situation was clearly caused in part by inbreeding and in part by isolation, two factors covered by this article. In any event, I think its time we revamped the backward evolution article and perhaps this one or other ones relating to it, so as to make it as factually and politically correct as possible. Please give your thoughts. Thomasiscool (talk) 23:25, 5 July 2008 (UTC)

There is not anything in Ulas family article to say that it is because of Inbreeding.--Lord Don-Jam (talk) 13:15, 6 September 2009 (UTC)

No one has got back to me and I cannot find anything so I am going to take out the bit about the Ulas family.--Lord Don-Jam (talk) 20:23, 25 September 2009 (UTC)

The ancient Greeks and the royal families among the ancient Egyptians practiced inbreeding and identified the cure for inbreeding depression. The cure is culling (preventing further reproduction by) the defectives. Aristotle said, "Nothing imperfect should ever be allowed to grow up," referring to infanticide. Many ancient peoples exposed their defective babies to natural predators, in order to maintain the purity of their gene stock free from deleterious recessive genes. While it is usually true that inbreeding without culling causes inbreeding depression, it is also usually true that inbreeding with sufficiently rigorous culling prevents inbreeding depression. Further, a practice of culling defective infants, continued over generations, removes deleterious genes from the gene pool and gradually reduces the rate of the culling necessary. I offer no moral judgment. I only say, "It works." Jenab6 (talk) 20:39, 29 June 2010 (UTC)

Dandelion and other asexually reproducing organisms

I removed this tag from the dandilion entry in the list on plants that tolerate inbreeding: . I removed the tag since, although there may be many species of dandelion, it is accepted that some of these are asexual (see Taraxacum). It is hard to find sources that describe exactly which species are asexual/apomictic and which are not, and whether asexual and sexual reproductive modes are strict in the species thus classified. I did find a relatively recent paper on the topic "Genetic structure of a population sample of apomictic dandelions" that states "Outside areas in Central Europe (Den Nijs and Sterk, 1980) and Asia (Richards, 1973), where diploid sexuals are found, dandelions are almost exclusively polyploid and obligate apomicts. Despite the lack of sexuals in these areas, it is not exceptional to find tens of different genotypes co-occurring in meadows, pastures or verges (Lyman and Ellstrand, 1984; Van der Hulst et al, 2000, and unpublished results)."

In short, I think dandelion should stand as a clear example of plants that tolerate inbreeding since, according to the quote above, common species produce seeds asexually and individuals are therefore maximally "inbred".