Non-coding DNA can be helpful in generating useful mutations that can go on to become new features/functionality of an organism. Non-coding DNA also indirectly reduces chances of mutation of useful/functional genes.
So if an organism has a larger proportion of non coding DNA it'll be safer from mutation. Humans have 80%-90% non-coding DNA. But this number is far lesser in many other species especially plants. Some plants have as few as only 3% non-coding DNA.
My question is, do these species with less non-coding DNA undergo evolution faster? Because their functional genes are more susceptible to mutations (which would be disadvantageous on average I guess). Would it be fair to say that evolution tries to keep expanding this proportion of buffer DNA? Lastly, is my question related to C-value paradox?
My assumption that non-coding DNA indirectly offers adaptive advantage (evolutionarily speaking) seems to be questioned. Let's consider the following case:
Let A and B be two genomes of equal size. Let A have 80 % non-coding DNA and 20% coding DNA. And let B have the opposite i.e., 20% non-coding DNA and 80% coding DNA. Let both A and B be exposed to the same amount of UV radiation for the same amount of time. All conditions being the same, let's assume that this causes the same amount of mutation in both A and B, say 10%. Now what is the probability that this mutation happened in non-coding DNA (which means it doesn't harm the organism) in each of A and B? Evidently, the probability is higher in A meaning it's safer from mutation caused due to UV radiation. So A has an advantage of surviving over B.