Sexual reproduction drove Ediacaran-to-Cambrian diversification surge via increased genetic variance

The Mitchell and Manica analysis of Newfoundland laser-scanned communities demonstrates that stolon-connected clones minimized local competition and maintained low alpha diversity for tens of millions of years. Once organisms adopted sexual reproduction, dispersal distances increased and offspring genetic variance allowed invasion of shallower, higher-stress habitats, producing the observed jump in beta diversity. This reframes the Cambrian explosion not as an external trigger but as the predictable outcome of a reproductive threshold crossing. Earlier work on rangeomorph modularity (e.g., Dunn et al. 2021, Proc. R. Soc. B) and molecular clock estimates placing bilaterian origins near 560 Ma (dos Reis et al. 2015, Curr. Biol.) converge on the same inflection point once sexual strategies are modeled explicitly.

Original coverage understated how asexual clonality also suppressed morphological innovation by limiting selection on recombinant genotypes. The new simulations quantify that sexual populations achieved equivalent resource use with 2.4-fold higher species richness under identical nutrient fields. This pattern aligns with later Phanerozoic radiations where sexual clades outpace asexual ones in disparity metrics. The study therefore supplies a mechanistic link between reproductive mode and the stepwise rise of metazoan complexity.

Future targeted searches for gamete or embryo fossils in 560–540 Ma sections, combined with spatial statistics from additional Ediacaran Lagerstätten, will test whether the modeled dispersal threshold is necessary and sufficient. Such data would also clarify whether the Ediacaran–Cambrian transition represents a singular reproductive revolution or repeated independent acquisitions of sex across stem lineages.