Skip to main content
Dryad

Data from: Inferring the evolution of reproductive isolation in a lineage of fossil threespine stickleback, Gasterosteus doryssus

Data files

Mar 20, 2024 version files 229.30 KB

Abstract

Darwin attributed the absence of species transitions in the fossil record to his hypothesis that speciation occurs within isolated habitat patches too geographically restricted to be captured by fossil sequences. Mayr’s peripatric speciation model added that such speciation would be rapid, further explaining missing evidence of diversification. Indeed, Eldredge and Gould’s original punctuated equilibrium model combined Darwin’s conjecture, Mayr’s model, and 124 years of unsuccessfully sampling the fossil record for transitions. Observing such divergence, however, could illustrate the tempo and mode of evolution during early speciation. Here, we investigate peripatric divergence in a Miocene stickleback fish, Gasterosteus doryssus. This lineage appeared and, over ~8,000 generations, evolved significant reduction of twelve of sixteen traits related to armor, swimming, and diet, relative to its ancestral population. This was greater morphological divergence than we observed between reproductively isolated, benthic-limnetic ecotypes of extant Gasterosteus aculeatus. Therefore, we infer that reproductive isolation was evolving. However, local extinction of low-armoured G. doryssus lineages shows how young isolate populations often disappear, supporting Darwin’s explanation for missing evidence and revealing a mechanism behind morphological stasis. Exctinction may also account for limited sustained divergence within the stickleback species complex and help reconcile speciation rate variation observed across time scales.