I’ve posted previously about the lionfish invasion that is threatening coral reef and other marine ecosystems throughout the Caribbean, Gulf of Mexico, and Southern Atlantic Seaboard of the United States.
Much has been made of the spectacular invasive success of the two species of Indo-Pacific lionfish that have established themselves throughout the Wider Caribbean. Not only are the invaders being found at population densities more than ten times those typical in their native range, but they also have been found to grow more rapidly, reaching sexual maturity more quickly, and growing to greater size than do their Indo-Pacific cousins.
Several studies have looked at the genetic make-up of invasive lionfish and have concluded that the populations found in the Gulf of Mexico, Caribbean, and Southeastern seaboard of the United States are all closely related, stemming back to fewer than ten females. A more recent study, which uses more sophisticated genetic testing techniques, not only sheds new light on the invaders, but also adds an unexpected twist to their saga. Up until now, it had been assumed that the invasive population was comprised of two closely related species; the red lionfish, Pterois volitans, and the devil fire fish, Pterois miles, with the former constituting that vast majority of the population, and with some evidence that the two species were beginning to hybridize in the invaded range.
However, a new study published in the Journal of Heredity and reported by Hakai Magazine finds that Pterois volitans is not in fact a distinct species, but rather is a hybrid of Petrois miles and the soldier lionfish, Petrois russelli, a species native to the Indo-Pacific from the eastern part of Africa to the Persian Gulf. The new finding lends further credence to the hypothesis that release (either accidental or intentional) of aquarium pets is the root of the invasion, as both Pterois russeli and Petrois miles are commonly sold as pets, and both have fairly wide native ranges.
Whereas previous studies had relied on mitochondrial DNA to determine species composition and degree of genetic diversity of the invasive population, the new study used nuclear DNA which, while more difficult to collect, provides a more complete picture of a population’s genetic make up.
The new finding may also help to explain the spectacular success of the invasive population. While they did not specifically test for this, the authors speculate that the high degree of hybridization of the lionfish found in the invaded range may point to a phenomenon known as heterosis, or hybrid vigor, wherein positive traits of hybrid offspring are enhanced as compared to those of their parents. In other words, the invasive population may constitute a sort of “superfish”. The authors note that further study is needed to confirm this hypothesis.
Whatever the explanation for the success of the invaders, their continued range expansion poses a significant threat to both biodiversity and livelihoods in the invaded range and requires integrated approaches to control, including development of markets for lionfish products. Follow this blog for further updates…