The influence of reproductive mode on resource competition and diversity patterns in Ediacaran early animal...

The appearance of the oldest known animals during the late Ediacaran period (~574 million years ago) was followed by a phase of slow diversification, until a later burst of rapid diversification known as the Ediacaran 'second wave'. The reasons behind the tempo of diversification are poorly understood. Here we investigate how reproductive mode mediated community dynamics and in turn Ediacaran macroevolutionary change. We show that widespread reproduction via stolon (namely via filaments connecting clones) limited within-species competition, leading to between-species competition acting at smaller spatial scales than within-species competition, a phenomenon called heteromyopia. Heteromyopia enables co-existence of suboptimal competitors because the dispersal limitation of the dominant species limits the occupation of the optimal habitat, so that lesser competitors can still exist within the same community, operating under reduced selection pressure. We explored the consequences of this dispersal limitation on community diversity using a mechanistic model showing that the change from stoloniferous to sexual reproduction that coincided with the second wave could explain the sudden increase in diversity observed in the fossil record. We conclude that widespread asexual reproduction via stolon probably constrained early animal evolution, limiting diversification until the onset of widespread sexual reproduction.