Within-Plant Distribution and Diversity of Mites Associated with the Invasive Plant Schinus Terebinthifolius (Sapindales: Anacardiaceae) in Florida
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PLANTÐINSECT INTERACTIONS Within-Plant Distribution and Diversity of Mites Associated with the Invasive Plant Schinus terebinthifolius (Sapindales: Anacardiaceae) in Florida 1 2 3 M. S. WIGGERS, P. D. PRATT, P. W. TIPPING, C. WELBOURN, AND J. P. CUDA Invasive Plant Research Laboratory, USDAÐARS, 3225 College Ave., Fort Lauderdale, FL 33314 Environ. Entomol. 34(4): 953Ð962 (2005) ABSTRACT The exotic Brazilian peppertree, Schinus terebinthifolius Raddi, is an invasive plant that readily displaces native vegetation and develops monospeciÞc stands in central and south FloridaÕs native ecosystems. Despite prior arthropod surveys of S. terebinthifolius in its adventive range, little is known concerning the acarofauna associated with the weed in Florida. Leaves of S. terebinthifolius also vary in the presence and development of domatia, which are small morphological structures that may beneÞt mites. We assessed the development of new mite associations with S. terebinthifolius in Florida and quantiÞed within-plant distribution of these arthropods. Mites inhabited over one-third of the sampled leaves with greatest species diversity in the Prostigmata, followed by Mesostigmata, Astigmata, and Cryptostigmata, respectively. Fungivorous mites (dominated by Lorryia formosa) were the most common feeding guild, predatory mites were the most diverse, and herbivorous mites were rarely encountered during the survey. Interior leaves supported greater populations of mites than exterior leaves, whereas height of leaves in the canopy did not affect mite distributions. Foliar domatia varied in development and occurred on nearly two-thirds of the leaves sampled. More than three- quarters of all mites collected were found on domatia-bearing leaves, which supported three times more mites per leaf than leaves without domatia. Mite densities increased concomitantly with the number of domatia, while domatia development only affected tydeids and number of leaves had no effect. The potential inßuence of domatia-mediated, tritrophic interactions among existing predators and a potential biological control agent of S. terebinthifolius are discussed. KEY WORDS Brazilian peppertree, Acari, Lorryia formosa, biological control, exotic weed BIOLOGICAL INVASIONS THREATEN NATIVE ecosystems by Myers and Bazely 2003). However, in most, if not all, altering hydrological and disturbance regimens, nu- systems, a small complex of indigenous fauna exploit trient cycling, energy budgets, and species diversity the exotic phylloplane, possibly inßuenced more by (Vitousek et al. 1997, Mack et al. 2000). Communities structural specialization than by plant species Þdelity dominated by exotic plants, for instance, are often (McMurtry and Croft 1997). The inßuence of exotic characterized by a paucity of indigenous faunal as- plant proliferation and concomitant changes in vege- semblages associated with the weed in its adventive tation structure on the development of new associa- range (Goeden 1974, Strong et al. 1984). Similarly, tions with opportunistic species remain largely unex- numerous studies have shown that a greater diversity plored. and abundance of natural enemies, speciÞcally herbi- Brazilian peppertree, Schinus terebinthifolius Raddi, vores, occur in a plantÕs native versus adventive range is a large (to Ͼ10 m), evergreen shrub or tree intro- (Goeden 1974, Balciunas and Burrows 1993, Memmott duced from Brazil as an ornamental into Ͼ20 countries et al. 2000, Costello et al. 2003). This enemy-free space (Ewel et al. 1982). In the United States, S. terebinthi- experienced by the invasive plant in its adventive folius is found in Louisiana, Texas, and California and range is a primary explanation for the efÞcacy of clas- is an aggressive weed in both Florida and Hawaii sical weed biological control, which seeks to reestab- (Ferriter 1997, Randall 2000, Hight et al. 2002). This lish top-down regulation of invasive plants by reunit- weed successfully colonizes many native plant com- ing a weed with coevolved natural enemies from its munities, including those supporting threatened and native range (Williams 1954, Keane and Crawley 2002, endangered species, and now occupies Ͼ283,000 ha in Florida (Ferriter 1997). A single hectare of suitable 1 Corresponding author, e-mail: [email protected]. habitat can support Ͼ2,500 S. terebinthifolius individ- 2 Florida Department of Agriculture and Consumer Services, Di- uals (Ewel et al. 1982), with disturbed habitats par- vision of Plant Sciences, PO Box 147100, Gainesville, FL 32614Ð7100. 3 University of Florida, Department of Entomology and Nematol- ticularly susceptible to invasion (Ewel 1986). The in- ogy, PO Box 110620, Gainesville, FL 32611Ð0620. vasion of this aggressive, woody weed poses a serious 954 ENVIRONMENTAL ENTOMOLOGY Vol. 34, no. 4 Table 1. Location of study sites used to quantify mite diversity associated with the invasive weed S. terebinthifolius in South Florida, Aug. 2000 to June 2001 Site County Latitudea Longitudea Months sampledb 1 Broward 26.17766 80.44888 IÐVI, VIIIÐX, XII 2 Palm Beach 26.65562 80.71247 IÐVI, VIIIÐX, XII 3 Hendry 26.75313 80.90704 IÐVI, IX, X, XII 4 Glades 26.9297 81.3142 IÐVI, VIIIÐX, XII 5 Hendry 26.59611 81.40956 IÐVI, VIIIÐX, XII 6 Collier 26.26348 81.3421 IÐVI, VIIIÐX, XII 7 Collier 25.89078 81.26965 IÐVI, VIIIÐX, XII 8 Collier 25.96463 81.35231 IÐVI, VIIIÐX, XII 9 Broward 26.14003 80.34463 IÐII, IVÐV, VII, XÐXII 10 Lee 26.42594 81.80995 IIÐVI, XI, XII 11 Collier 26.10345 81.63334 IIIÐVI, XI, XII 12 Miami-Dade 25.6885 80.497111 IIÐVI, IXÐXII a Decimal degrees. b Roman numerals correspond to months with I ϭ Jan. through XII ϭ Dec. each site in a randomly stratiÞed method; 3 leaves were removed at each of three heights (low, Ϸ0.5 m; mid, Ϸ1 m; high, Ϸ2 m) from the exterior of the plant Fig. 1. Schinus terebinthifolius study sites in South Flor- canopy, near the branch apex, and from within the ida. interior of the plant canopy, Ϸ1 m from the branch apex. Each sample was sealed in a polyethylene bag, threat to species diversity and was identiÞed in 1969 as transported to the laboratory, and observed under a having the potential to degrade many of South Flor- binocular microscope at ϫ40 magniÞcation within idaÕs natural areas (Morton 1978). 48 h. Mite diversity, abundance, developmental stage Despite several surveys of S. terebinthifolius (Ewel (egg, juvenile, or adult), and domatia development et al. 1982, Cassani 1986, Cassani et al. 1989) in its were recorded. To further quantify morphological adventive range, relatively little is known concerning variation, number of leaßets and domatia per leaf were the development of new arthropod associations with recorded from December 2000 to June 2001. Adult this invasive plant in Florida. Of the three previous mites for each species were mounted on glass slides in surveys, only Cassani (1986) reported mites associated HoyerÕs media for identiÞcation. Voucher specimens with the invasive plant, but these accounted for Ͻ4% were deposited in the acarological collection of the of the 115 arthropod species encountered. Some Florida Department of Agriculture and Consumer leaves of S. terebinthifolius possess domatia (Pember- Services, Division of Plant Industry in Gainesville, FL. ton and Turner 1989), which are known to inßuence The glabrous, compound leaves of S. terebinthifolius mite populations (Walter 1996). Studies have found have slightly rolled margins, and the petioles are often that plants with domatia support greater populations winged. First characterized by Pemberton and Turner of mites than those without domatia (Walter and (1989), domatia of S. terebinthifolius are auriculate OÕDowd 1992a, Rozario 1995, OÕDowd and Willson folds in the leaf lamina occurring on the abaxial side 1997). Given that mites represent one of the largest at the junction of the petiole and leaßet (Fig. 2a). taxonomic groups of arthropods (Walter and Behan- However, we have observed variation in the occur- Pelletier 1999, Walter and Proctor 1999) and their rence and degree of development of domatia on S. afÞnity for foliar domatia, it is surprising that so terebinthifolius and categorized domatia development few mites have been reported to be associated with as undeveloped (ßat, Fig. 2b), partially developed S. terebinthifolius in the literature (i.e., Ewel et al. 1982, (Ϸ50% curled, Fig. 2c), or fully developed (over- Cassani 1986, Cassani et al. 1989). In this study, we topped curl, Fig. 2d). For scanning electron micro- sought to (1) assess the diversity of acarofauna asso- graphs, domatia were Þxed with 3% glutaraldehyde in ciated with S. terebinthifolius in Florida and (2) quan- 0.2 M potassium phosphate buffer and postÞxed with tify within-plant distribution of these mites. 2% osmium tetroxide in 0.2 M potassium phosphate buffer, dehydrated in an alcohol series, critical-point dried, sputter-coated with gold/palladium, and ob- Materials and Methods served with a Hitachi S530 scanning electron micro- Acarological surveys of S. terebinthifolius were per- scope (Hitachi High Tech Am. Inc., Pleasanton, CA). formed at 12 locations in South Florida (Fig. 1; Table Mite counts were normalized using a ln(x ϩ 1) 1) from August 2000 through June 2001. All sites were transformation before analysis to meet assumptions of located in disturbed areas along roadsides and canal normality and homogeneity of variances implicit in rights-of-way. Trees of similar size and vigor were the parametric analysis. Mite data were grouped by sampled without apparent bias. Sampling