|Variation Among Melaleuca quinquenervia (Myrtaceae) Populations in Florida and Its Influence on Performance of the Biological Control Agent Oxyops vitiosa (Coleoptera: Curculionidae)
F. Allen Dray Jr.
USDA, ARS Invasive Plant Research Laboratory; Fort Lauderdale, FL
Melaleuca quinquenervia (Cav.) Blake (Mytaceae) was imported into Florida over a century ago as a landscape plant. A favorable climate and periodic wildfires helped M. quinquenervia thrive; it now occupies about 200,000 hectares in southern Florida. Careful scrutiny of early horticultural catalogs and USDA plant introduction records suggests at least six distinct introduction events. Allozyme analyses indicate that the pattern of these introductions, and the subsequent redistribution of progeny, have resulted in geographic structuring of the populations in southern Florida. For example, trees on Florida’s Gulf Coast have a greater effective number of alleles and exhibit greater heterozygosity than trees on the Atlantic Coast. Essential oil yields from M. quinquenervia leaves follow a similar trend; Gulf Coast trees yield nearly twice as much oil as Atlantic Coast trees when both are grown in a common garden. These differences are partially explained by the predominance of a chemical phenotype (chemotype) very rich in the sesquiterpene trans-nerolidol in M. quinquenervia trees along the Gulf Coast, but rich in a mixture of the monoterpene 1,8-cineole and the sesquiterpene viridiflorol in trees along the Atlantic Coast. Performance of the imported biological control agent Oxyops vitiosa differed dramatically in laboratory studies depending on which chemotype they were fed. Larval survivorship was fourfold greater on the trans-nerolidol chemotype. Growth was also greater, with adult O. vitiosa gaining nearly 50% more biomass on the trans-nerolidol plants than on the second chemotype. We are currently investigating whether these differences can be detected in the field.
Dray, F. Allen Jr.; USDA, ARS Invasive Plant Research Lab; 3205 College Avenue, Fort Lauderdale, FL 33314
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