OUR impact on the environment may be forcing evolution into reverse, collapsing recently formed species back into a single one. This “reverse speciation” may be robbing evolution of the raw material for future biodiversity.
For a species to split into two, something must block the flow of genes between the two incipient species. This happens when a physical barrier prevents gene flow, as when two populations end up on different islands, or become separated by inhospitable habitat. Another driver is behavioural differences: different breeding seasons, say, or insects choosing different food plants to live on can also set two lineages…
