Geographic range expansion of Oxyops vitiosa (Coleoptera: Curculionidae) to the Bahamian Archipelago

The Australian tree Melaleuca quinquenervia (Cav.) Blake was internationally disseminated over the last century for ornamental and agrofor estry purposes (Dray et al. 2006). Although intro duced into California, Texas, and Louisiana, it has not been reported as an invasive pest in those areas. In contrast, it has proven to be a superior competitor to most native vegetation in wetlands of Florida, Puerto Rico, Cuba, and the Bahamas (Pratt et al. 2005b; Pratt et al. 2007; Turner et al. 1998). A biological control program in Florida target ing M. quinquenervia was initiated in 1986 (Bal ciunas et al. 1994). The weevil Oxyops vitiosa Pascoe and the psyllid Boreioglycaspis melaleu cae Moore were among the first natural enemies selected for pre-release risk assessments (Pur cell & Balciunas 1994). Host range testing indi cated that both herbivores only completed devel opment on a small group of species in the Mela leuca genus, of which there are no native repre sentatives in the New World. The weevil and psyllid were permitted for release in south Flor ida during the spring of 1997 and 2002, respec tively. Both species established in M. quinquen ervia dominated habitats (Pratt et al. 2003; Cen ter et al. 2007). Herbivory from introduced biological control agents resulted in significant reductions in M. quinquenervia growth, reproduction, and survi vorship (Pratt et al. 2005a; Franks et al. 2006; Morath et al. 2006; Center et al. 2007; Tipping et al. 2008). These impacts collectively limited the competitive superiority of M. quinquenervia and led to increases in native species diversity in hab itats once dominated by it. In response, federal, state, and county agencies initiated a redistribu tion campaign for O. vitiosa and B. melaleucae. To date, >3 million individuals have been redistrib uted to nearly 407 locations in southern Florida. Biotic exchange between the Florida mainland and neighboring island systems is an increasingly common occurrence (Dobbs & Brodel 2004). We questioned whether O. vitiosa and/or B. melaleu cae had dispersed to the neighboring West Indies. To address this question we surveyed M. quin quenervia dominated wetlands of Puerto Rico and discovered the presence of P. melaleucae in 2006 (Pratt et al. 2007). The occurrence of the psyllid in Puerto Rico, some 1300 km from the originating population in Florida, led us to hypothesize that the Australian herbivores may have dispersed to M. quinquenervia stands on the nearby islands of the Bahamian archipelago. Recent aerial and ground vegetation assess ments quantified the geographic distribution of several exotic plant species, including M. quin quenervia, on Grand Bahama, New Providence, and Andros islands of the Bahamas (Fig. 1; Pratt et al. 2007). Using coordinates from these assess ments, we surveyed all known M. quinquenervia populations or individuals for the Australian her bivores during Dec 2005 and Mar 2007. Trees were examined by 3 observers for 15 min each to detect presence, estimate feeding damage, and determine the proportion of trees infested. Feed ing damage was assessed on a 5-point scale based on visual estimation of percentage of suitable foli age destroyed by feeding: 0 = no damage; 1 = <25% destroyed; 2 = 26 to 50%; 3 = 51 to 75%; 4 = 76 to 100% destroyed. The proportion of damaged trees within a given site was estimated and aver aged within site. Eight sites on Andros, 22 on Grand Bahama, and 20 on New Providence containing M. quin quenervia were surveyed (Fig. 1). No evidence of either insect was observed in the 2005. Similarly, B. melaleucae was absent in the 2007 survey but O. vitiosa was observed at 6 locations on New Providence (Fig. 1). Identification of O. vitiosa was confirmed by Mike Thomas (Florida Department of Agriculture and Consumer Services, Gaines ville, FL) and voucher specimens were deposited in the Florida State Collection of Arthropods. Geographic distribution of O. vitiosa was lim ited to the southern half of New Providence (Fig. 1). Herbivory was greatest at site 1, withM. quinquenervia trees experiencing 25-50% dam age, and having the highest proportion of trees at tacked by the weevil (60%). Less than 10% of trees were damaged at the 5 other sites. If we assume that damage levels and the proportion of trees at tacked correlate with time since establishment, these data suggest a point of introduction for O. vitiosa at or near the village of Adelaide and adults spread from these trees to surrounding M. quinquenervia stands. Discovery of O. vitiosa in the Bahamas raises questions regarding pathways of introduction. How might O. vitiosa disperse from Florida to New Providence? Proximity and widespread oc currence of M. quinquenervia among the Baha mian islands may have allowed unassisted dis persal from Florida. It is possible that hurricanes facilitate dispersal of insects through the Carib bean (Drake & Farrow 1988). Hurricane Wilma in Oct 2005 crossed southern Florida and made landfall in the Bahamas. New Providence lies ap