Cell-level selection and inheritance of acquired mutations

Question

I was reading about different levels of selection in Ridley's Evolution textbook (chapter on units of evolution) and saw that some organisms e.g. carrots are not Weismannist i.e. don't have separate somatic and germ lines and can make offspring with their somatic cells, and that this can in theory lead to cell-level selection because cell lines that outcompete others have a greater chance of leading to offspring and thus will be selected for. I think mutation that arises in a cell during the organism's lifetime and causes it to proliferate counts as an acquired mutation, but I've also read a lot that acquired mutations/characters aren't passed on a la Lamarck.

Is this a case where acquired mutations are passed on, and how does that fit with the usual concept that acquired characters aren't passed on? I know gene, individual, and kin selection are much more prevalent and Ridley says the cell-line selection idea is just theoretical, but what would this mean if it occurred?

Thanks :)

Answer 1

In any reproductive event, we transmit new mutations to the offspring. In absence of cell-line selection, whether the mutation occurred during a meiosis or a mitosis is of little interest.

In absence of cell-line selection

A big difference between acquired mutations and Lamarck's acquired inheritance is that under Lamarck's view point, characters are being adaptive. Under Lamarck's view point, individual try to perform some action, stretch their muscles and other organs toward what is optimal for their needs and this phenotypic modification is being transmitted. The classical example is the example of giraffes. Giraffes stretch their neck trying to reach for high leaves, their neck is getting longer and their longer neck is being transmitted to their babies.

With acquired mutations, in absence of cell-line selection, there is no reason for adaptive mutations to be transmitted more often than non-adaptive one.

With cell-line selection

Now, if there is cell-line selection, beneficial mutations (beneficial at the cell level) are more often transmitted. The mutational process itself stil remain "random" (see Are mutations random?) but selection will increase the ratio of beneficial to deleterious mutations. Now, mutations that are beneficial at the cell level are not necessarily beneficial at the organism level. A typical example is cancer.