Genetic and Morphometric Discrimination of Coastal and Inland Tabanus lineola (Diptera: Tabanidae) S. J. SCHUTZ, R. R. GAUGLER, 1 AND R. C. VRIJENHOEK 2 Department of Entomology, Rutgers University, New Brunswick, New Jersey 08903 Ann. Entomol. Soc. Am. 82(2): 220-224 (1989) ABSTRACT A population-genetic study of adult female Tabanus lineola F. from New Jersey and Louisiana determined that the coastal and inland "varieties" T. lineola hinellus Philip and T. lineola lineola F. are reproductively isolated and represent distinct species. Diagnostic differences were found at 4 of 11 gene loci surveyed. Nine individuals were genetically distinct from all other specimens and may represent a third cryptic species. Stepwise discriminant analysis was used to produce a taxonomic key for separation of the coastal and inland species based on four easily measured morphological characters. The degree of separation achieved was greater for specimens collected in Louisiana. KEY WORDS Insecta, population genetics, electrophoresis, discriminant analysis CRYPTIC SPECIES are those not distinguishable by conventional taxonomic methods, because of a lack of readily identifiable differences in morphology. In addition to being of concern to taxonomists, the presence of undiagnosed cryptic species has serious implications for pest management. Ecological, be- havioral, or physiological differences among cryp- tic populations can render control measures de- signed to be effective against one species ineffective against another. This can result in partial or com- plete failure of the control program, and also might exacerbate pest problems by freeing the sibling species from competition and allowing its popu- lation to expand (Makela & Richardson 1978). Cryptic species are an especially important concern in control of medically important pests, because they may differ significantly in their vector poten- tial, habitat, or host seeking behavior. The Tabanus lineola complex, commonly known as the lined horse flies, has posed serious problems to taxonomists, because of extreme morphological variation, lack of ecological information, and in- sufficient material in collections (Fairchild 1983). Tabanidae have few distinctive characters; most of these are confined to the head and to color patterns (Pechuman 1981). Male genitalic structures have not been studied (Fairchild 1983), because genitalic differences do not appear to be diagnostically use- ful in identification below the level of tribe. Philip (1942)firstrecognized the possibility that T. lineola F. included more than one species, and he subse- quently separated T. similis Macquart and T. sub- similis Bellardi. Philip (1960) later described T. lineola hinellus Philip as a coastal variety of T. lineola. Pechuman (1973) also noted the existence 1 Department of Entomology and Economic Zoology. 2 Center for Theoretical and Applied Genetics. of two forms of Tabanus lineola characterized by a broad or narrow frons and associated with coastal and inland habitats, respectively. Fairchild (1983) suggested a clinal relationship between frons width and habitat: the northern and inland specimens are darker in color and have a narrower frons. He tentatively treated the broad fronted (coastal) flies and the narrow fronted (inland) flies as subspecies, T. lineola hinellus Philip and T. lineola lineola F., stating a need for further investigation using more refined techniques. In cases where morphological distinctions are insufficient, electrophoresis of enzymes is a valu- able technique for differentiating cryptic species (Miles 1978, Jacobson et al. 1981). Once specimens can be sorted on the basis of genetic differences, multivariate statistical techniques can be used to produce a practical key based on diagnostic com- binations of morphometric characters (Sofield et al. 1984b). In this study, we provide genetic evidence that T. lineola hinellus and T. lineola lineola are distinct at the species level. In addition, we provide a key based on four morphometric characters for identification of the two species. Materials and Methods Coastal T. lineola females were collected in 1983 at Cedarville, N.J., and Chack Bay, La., in black box traps. Inland flies were collected in malaise traps at Great Swamp, N.J., and Elmer's Isle, La. Samples were returned to the laboratory on dry ice and maintained at -80°C until analyzed. Before electrophoretic examination, we record- ed the total body length of each fly and removed the head for later morphometric analysis. The re- maining portion (thorax and abdomen) of each fly was homogenized individually in 0.4 ml of grind- A 0013-8746/89/0220-0224$02.00/0 © 1989 Entomological Society of America at New York University on April 12, 2016 http://aesa.oxfordjournals.org/ Downloaded from