To the best of my knowledge, the current atmosphere of Mars, to the extent it has one at all, cannot sustain us. Presumably then you are presuming some sort of terraforming. If the atmosphere is terraformed, there is no reason to believe that it will differ in chemical makeup from that of Earth. The big difference will be density due to the lower gravity. People with larger lungs or a more efficient respiratory system would have an advantage. But is it not at all clear that being able to labor more effectively in the field will give someone a reproductive advantage. Less advantaged individuals working in an office environment could compensate with a breathing aid.

The varieties of plants that humans eat do not evolve by natural selection. They evolve by artificial selection. That artificial selection is more driven by culture than by dietary needs. For example, maroon carrots have more beta carotene and are sweeter than orange carrots, but people think they're weird so they've never caught on. I suspect humans on Mars will develop strains of terrestrial plants that taste and look as much like the ones they left behind on Earth as agricultural science can achieve.