Intraspecific variation of Melaleuca quinquenervia leaf oils in its naturalized range in Florida, the Caribbean, and Hawaii

The invasive tree Melaleuca quinquenervia threatens the biodiversity of the Florida Everglades and adjacent areas. Biological control efforts have resulted in the release of three Australian insect species. Not all populations of the plant, however, are equally nutritious to the biological control agents. For example, previous results indicated that Oxyops vitiosa had reduced biomass and fecundity when fed different M. quinquenervia chemical variants. To find suitable sites for release of this herbivore species and locations where nursery sites can be developed for mass production of weevils, we studied the natural terpenoid variation in this plant throughout its range in Florida. For comparison, we also examined the terpenoid variation in naturalized populations in the Caribbean, Hawaii, and Australia. We found that two chemical variants or chemotypes exist in Florida, each dominated by one sesquiterpene, either E-nerolidol or viridiflorol. In the 28 populations studied in Florida no regional trends in chemotype dominance were found. More than half (16 of 28) of the populations were composed of between 34 and 66% of both chemotypes. A similar number of populations were dominated (>66%) by either the E-nerolidol (eight populations) or the viridiflorol (six populations) chemotype plants. Additionally, the total amount of terpenoids in leaves from plants grown north of the invasive range of M. quinquenervia was significantly reduced compared with invasive populations. The total amount of terpenoids in leaves from plants grown in Australia and the Caribbean was significantly greater than those in leaves from Florida and Hawaii. These results identified eight populations that would be most suitable for initial releases and where field nurseries could be established for on-site mass production.