Evidence for sympatric speciation by host shift in the sea

New species most commonly evolve when populations become geographically isolated (allopatric speciation). The idea that new species can also evolve within the range of a single population (sympatric speciation) has been around since the time of Charles Darwin, but the idea remains controversial in part, because there are few good examples. Using a combination of genetic, ecological, and biogeographic studies, researchers have found that a new species of reef fish might have evolved when some individuals of the ancestral population began inhabiting a novel species of coral and that this "host shift" could have happened without geographic isolation of the new population.

Philip Munday and colleagues at James Cook University, Australia, used genetic analyses to show that a new species of coral-dwelling goby discovered in Papua New Guinea is closely related to another species of goby found in the same area and that the two species diverged from each other just a few hundred thousand years ago. The new goby species inhabits just one species of coral--one that is not used by any other goby species. Although various mechanisms of speciation are possible, the authors show that sympatric speciation by host shift is the simplest explanation for the pattern of habitat use and current-day geographic range of the new species. The ecology of coral-dwelling gobies closely matches that of leaf-eating insects, another group of animals for which sympatric speciation by host shift has been reported, thus providing support for a general set of ecological conditions that favor sympatric speciation by host shift.

Philip L. Munday, Lynne van Herwerden, and Christine L. Dudgeon: "Evidence for Sympatric Speciation by Host Shift in the Sea"

Publishing in Current Biology, 24 August 2004, Volume 14, Issue 16, pages 1497-1504.

---

---