Melissa R. Martin

Weevils Versus No Weevils: A Comparison of Salvinia minima Populations in Florida and Louisiana

Cyrtobagous salviniae Calder and Sands (Coleoptera: Curculionidae) is a successful biological control agent of aquatic weeds suppressing species like giant salvinia, Salvinia molesta D.Mitch. (Salviniales: Salviniaceae), in at least 15 countries over 3 continents (Julien et al. 2002). There are at least 2 ecotypes of this insect; the smaller Florida ecotype found on common salvinia, S. minima Baker, throughout Florida, and the larger Brazil ecotype, which has been used extensively against S. molesta (Jacono 2001). Despite initial questions about the identity of the Florida ecotype (Goolsby et al. 2000), molecular work has confirmed that the 2 ecotypes represent a single species (Madeira et al. 2006). Although S. minima causes significant problems in Louisiana, it rarely forms persistent mats in Florida (Tipping et al. 2012). This regional difference may be caused by herbivory by the Florida weevil ecotype, which was first reported in Florida in 1962 (Kissinger 1966). The goal of this study was to compare population variables of S. minima between freshwater swamp forest habitats located in different states where one (Louisiana) lacks C. salviniae. Generalist herbivores like Synclita oblteralis (Walker) (Lepidoptera: Crambidae) and Samea multiplicalis Guenee (Lepidoptera: Crambidae) are present on S. minima in both states (Munroe 1972; Knopf and Habeck 1976). Environmental, plant, and insect variables were compared between 4 field sites in Florida and 5 in Louisiana during 11 dates between 2002 through 2004. Florida sites were located near Immokalee, West Palm Beach, and LaBelle while Louisiana sites were located within the Barataria preserve south of New Orleans. In Florida,

Response of Two Chemotypes of Melaleuca quinquenervia (Myrtales: Myrtaceae) Saplings to Colonization by Specialist Herbivores

Abstract Two chemotypes of Melaleuca quinquenervia (Cav.) S. T. Blake (Myrtales: Myrtaceae) saplings were planted in a common garden under 2 water treatments and exposed to either restricted or unrestricted herbivory from 2 insect herbivores. Chemotypes consisted of either a predominately E-nerolidol terpenoid complex or one that consisted primarily of viridiflorol; both types had influenced the performance or preference of both insect herbivores in laboratory studies. The densities of the 2 specialist herbivores Boreioglycaspis melaleucae Moore (Hemiptera: Psyllidae) and Oxyops vitiosa Pascoe (Coleoptera: Curculionidae) were monitored regularly as they colonized the plantings, as were plant responses like leaf abscission and tree height. Neither the chemotype nor the water treatments influenced the densities of B. melaleucae and O. vitiosa. Trees subjected to unrestricted herbivory shed more leaf biomass than those protected by insecticides from herbivory. There was no relationship between the amount of biomass shed via abscission and the density of either herbivore despite a significant correlation with a damage rating developed for O. vitiosa. There was a chemotype response to herbivory whereby more leaf biomass was shed by the E-nerolidol chemotype than by the viridiflorol chemotype when subjected to unrestricted herbivory. Tree height was influenced by herbivory but not chemotype or water, although there were separate 2-way interactions between all factors. Thus, despite equal herbivore pressure, the response of young M. quinquenervia trees to abiotic and biotic forces diverged at the plant variant level.