Isn’t species fitness somewhat weak, though? I would want to think about this in terms of gene fitness. Over long periods of time, in different situations, genes that promote one strategy or the other will dominate part of the time and lose part of the time.
it is manifestation of a physical law at a higher level of organization.
it is gene fitness, except the observer is focused on species population level dynamics rather than individual level dynamics.
they may look very different however the fundamental mechanism is contribution of a biopolymer to variations of biological fitness