For example, there is a segregation-distorter on the male sex chromosome of some mice which causes only male children to be born, all carrying the segregation-distorter.
Which locus is this?
Oh, and here's some data on fox reproduction. What would you expect X and Y to be before checking the actual data?
-Of the X to X+1 cubs born to an average fox litter, an average of Y to Y+1 survive the first year.
Windy, the point you referred to from Caledonian is not different than my own, so clearly it is you who is misunderstanding something here.
Your scenario is plausible, it's just not group selection. It's K selection. Just because "group" is mentioned in the scenario doesn't make it group selection.
Your definition also makes every adaptation that rescues a group from extinction an example of group selection. What's special about reproductive restraint? Antibiotic resistance is group selection, since otherwise that population would go extinct. Industrial melanism is group selection, since otherwise that population would(might?) go extinct.
Remember, if the degree to which the individual was able to survive decreased, if it was actual decreased fitness, we arrive back at the paradox where somehow the group is flourishing while all the individuals of that group are dead.
"Actual decreased fitness" does not mean "all will die". If it is logically impossible for "actual decreased fitness" to evolve, how do you explain worker ants? (ignore for the moment whether it's kin or group selection or what, just consider what the fitness of the workers is.)
T gene is one scientific name of the variant - or rather "t haplotype". Geneticists are not as anal about names as taxonomists...
Caledonian is right, it's not a "fillip" to point out that reproductive restraint can evolve by individual selection in the sense of K-selection, not in the sense of altruism. To be fair, several recent articles in favor of group selection also talk about "reproductive restraint" and mean altruism, but that doesn't IMO excuse it. Any adaptation leading to late reproduction and less offspring in, say, elephants, must have looked like "reproductive restraint" at some point (although not necessarily at the level of numbers of grandkids, which is the true measure of fitness).
Wiseman's misunderstanding of group selection demonstrates why this would have been an important distinction to make.
Caledonian: ...mice don't go extinct even though they're parasitized by the replicator gene. Sure, the gene rapidly dominates any group it's introduced to, and prevents successful reproduction within that group, but there are enough obstacles to divide the total mouse population into smaller groups in the short term.
I think you are wrong about the mouse t gene, though. Individual selection is working against gene selection within each mouse population. I haven't seen accounts that group selection is necessary here, or do you have a ref?
I wish I could have found the link on Trivers I was half-recalling though.
Could it be something like this exchange between Trivers and the authors of "Unto Others". Some of the comments from Trivers are priceless.
"You are in way over your head on this one. It is clear that you are behind on current literature. The "selfish gene" is old hat and out of date. Multi-level evolution is increasingly widely accepted by many geneticists, with such mechanisms as reciprocal altruism being keys."
Perhaps you shouldn't be so hasty at pointing the "over your head" finger at others. Reciprocal altruism is NOT about multilevel selection. It's good old individual selection - helping others on the assumption that the help will later be returned. This explanation assumes a fitness benefit (on average) for each participating individual, invoking group selection here is not necessary.