Delving into the origins of tropical marine biodiversity
For a time, biologists believed that marine animals who arrived in Hawaii and evolved into unique Hawaiian species were living in what they called an “evolutionary graveyard,” meaning the species had hit the end of the line.
However new research is showing that Hawaiian marine animals are radiating back across the ocean, spreading their genes and adapting to new environments as part of a complementary process of biodiversity feedback.
“What we’ve shown with genetics—by finding out who’s related to who across the Pacific—is that Hawaiʻi can export biodiversity, and that it does contribute to the overall biodiversity of the Indo-Pacific,” said Professor Brian Bowen of the University of Hawaiʻi at Mānoa’s Hawaiʻi Institute of Marine Biology (HIMB).
Bowen and his colleagues at HIMB and the California Academy of Sciences have identified a growing body of evidence that oceanic archipelagos are actively exporting genetic and biological diversity.
The yellow tang (lauʻīpala) is Bowen’s favorite example of a Hawaiian species on the move. This bright yellow reef fish is spotted by snorkelers on all of the major Hawaiian Islands. HIMB researcher Jeff Eble (now at University of West Florida) found that yellow tang ecology, historical demography, and genetics point to a Hawaiian origin several hundred thousand years ago. Now they occur as far away as Japan.
Other Hawaiian creatures venturing out to ply new waters include the ember parrotfish (uhu), the Hawaiian pink snapper (opakapaka), and the lollyfish sea cucumber (loli).
“When species forged in the flames of competition arrive in an area of ecological release like Hawaiʻi, they have the space to try new things,” Bowen said. “It’s called niche expansion. These new capabilities allow the species to in turn expand out and contribute to high biodiversity elsewhere in the Pacific.”
Lead author Bowen and his colleagues recently published their findings on biodiversity feedback in the scientific journal Trends in Ecology & Evolution. The paper also highlights how physical isolation is not the sole avenue for marine speciation—many species diverge along ecological boundaries.
The discovery of these evolutionary pathways has applications to the conservation of coral reef ecosystems. In 2006, the entire 2,000 kilometers of the northwestern Hawaiian Islands was protected as the Papahānaumokuākea Marine National Monument. This sanctuary was designed to protect the unique biodiversity of Hawaiʻi, but the new research shows that Papahānaumokuākea incubates new biodiversity as well.
UH Mānoa is taking a lead role in genomics research to explore the origins of marine biodiversity. “Genomics will reveal which genes are responsible for evolutionary divergences that are the foundation for biodiversity,” Bowen said.