The evolution and fate of diversity under hard and soft selection - all data and code

How genetic variation arises and persists over evolutionary time despite
the depleting effects of natural selection remains a long-standing
question. Here, we investigate the impacts of two extreme forms of
population regulation – at the level of the total, mixed population (hard
selection) and at the level of local, spatially distinct patches (soft
selection) – on the emergence and fate of diversity under strong divergent
selection. We find that while the form of population regulation has little
effect on rates of diversification it can modulate the long-term fate of
genetic variation, diversity being more readily maintained under soft
selection compared to hard selection. The mechanism responsible for
coexistence is negative frequency dependent selection which, while present
initially under both forms of population regulation, persists over the
long-term only under soft selection. Importantly, coexistence is robust to
continued evolution of niche specialist types under soft selection but not
hard selection. These results suggest that soft selection could be a
general mechanism for the maintenance of ecological diversity over
evolutionary time scales.