"Our data show a very clear shift in evolutionary processes that coincides with a shift in Earth systems dynamics," researcher Alycia Stigall, a paleontologist at Ohio University, told LiveScience." In particular, these results shed light on the Earth system controls on how new species form, or speciation."
As geological changes slowly unfolded in Laurentia over the course of a million years, the fossils suggest two patterns of survival emerged among the creatures there.
During the early stage of the changes, native organisms became geographically divided, slowly evolving into different species suited for their different habitats. This process, called vicariance, is the typical method by which new species develop on Earth, Stigall said.
However, as these geological changes progressed, species from other regions of Laurentia began to directly invade habitats, a process called dispersal. Although biodiversity increased at first, dispersal reduced biodiversity in the long term, because it permitted a few aggressive species to populate and dominate many sites quickly, Stigall explained.