ECOLOGY AND POPULATION BIOLOGY Novel Analysis of Spatial and Temporal Patterns of Resource Use in a Group of Tephritid Flies of the Genus Anastrepha 1 2 3 4 JOHN SIVINSKI, MARTIN ALUJA, JAIME PIN˜ ERO, AND MARIO OJEDA Center for Medical, Agricultural and Veterinary Entomology, USDAÐARS, P.O. Box 14565, Gainesville, FL 32604 Ann. Entomol. Soc. Am. 97(3): 504Ð512 (2004) ABSTRACT The spatial and temporal patterns of oviposition-resource use of various Anastrepha spp. fruit ßies within the canopies of individual fruit trees were determined over periods of 4Ð6 yr in the state of Veracruz, Mexico. The ßies examined were Anastrepha obliqua (Macquart), Anastrepha striata Schiner, Anastrepha fracterculus (Wiedemann), and Anastrepha alveata Stone, and their respective hosts were Spondias mombin L. (Anacardiaceae), Psidium guajava L., Psidium sartorianum (Berg.) Ndzu (Myrtacaea), and Ximenia americana L. (Olacaceae). The canopies were divided into six sectors: three strata (vertical planes of low, middle, and high canopy) and an exterior and interior component of the various heights. All ripe fruits produced by each tree species were individually harvested, weighed, and maintained until all larvae had exited and pupated. Because of the commonly positive correlation between fruit size and infestation, ßy distributions were described using a novel technique, two-level hierarchal regression analysis, as deviations fromthe expected numbersof insects in a sector given the distributions of fruit weights within the canopy. Overall, there was a tendency for A. alveata to be more abundant in the lower portions of the tree, for A. striata to be more abundant in the upper, for A. obliqua to be less abundant in the upper, and for A. fraterculus to be uniformly distributed. The yearly densities of A. striata and A. fraterculus within the P. guajava tree were negatively correlated, and this seems to be due to annual changes in environment rather than to exploitive competition for oviposition resources. Along an altitudinal gradient (0Ð1,800 m), A. striata was more abundant than A. fraterculus at sea level and relatively less abundant at altitudes of 1000 mand higher. We suggest that habitat characteristics (oviposition-resource availability and quality, and microclimatic variables), intraspeciÞc competition, and the behaviors of natural enemies and frugivores are potentially im- portant interactive factors that inßuence the distribution of resource use to a different extent in each of the tephritid species. KEY WORDS resource use, spatial distribution, competition, habitat partitioning, altitudinal transect THERE ARE TWO FORMS of ecological complexity (Earn sequences that in turn inßuence land use, insecticide and Rohani 1999): complexity due to interactions use, and the conservation of biological diversity (Aluja among species (ecosystem complexity) and that 1999). which arises fromchanging patterns of abundance Dynamic patterns of resource use by herbivorous over space and time (dynamical complexity). Descrip- insects are inßuenced by variance in the distribution, tions of dynamical patterns of resource use are rela- availability, and quality of resources (Chew 1977). In tively rare because they often require detailed obser- fruit-infesting tephritids such as Anastrepha spp., high vations of habitat variance made over long periods. At variance in oviposition-resources on spatial and tem- the same time, they are critical for better understand- poral scales might lead to discontinuous ranges, ge- ing the distributions and abundances of organisms. In netic divergence among populations, and coarse- the case of Anastrepha spp. fruit ßies, distributions and grained patterns of abundance within habitats. In abundances can have considerable agricultural con- terms of individual insects, variance and unpredict- ability may result in the evolution of behavioral plas- 1 E-mail: [email protected]ß.edu. ticity, the capacity to monitor environmental changes, 2 Instituto de Ecologõ´a, A. C. Apartado Postal 63, 91000 Xalapa, and competitive adaptations such as host-marking Veracruz, Mexico. pheromones that help use occasional windfalls (Aver- 3 Department of Entomology, University of Massachusetts, Am- ill 1985, Aluja et al. 2000, Dõ´az-Fleischer et al. 2000, herst, MA 01003. Dõaz-Fleischer and Aluja 2004). The following are 4 Laboratorio de Investigacio´n y Asesorõ´a Estadõ´stica (LINAE), ´ Facultad de Estadõ´stica, Universidad Veracruzana. Apartado Postal among the speciÞc sources of resource variance con- 475, 91000 Xalapa, Veracruz, Mexico. fronting Anastrepha spp. fruit ßies. May 2004 SIVINSKI ET AL.: RESOURCE USE PATTERNS IN Anastrepha SPP. 505 First, there is the distribution of host fruits. Many basic knowledge of insectÐhost interactions and in- species, particularly those with broad host ranges, will teractions among competing species of fruit ßies. Þnd oviposition resources in disparate habitats such as From an agricultural perspective, it may help make patches of tropical evergreen or deciduous forests, better predictions of the potential range of invasive large monocrop orchards, and mixed orchards or back- pests and improve sampling regimes for management yard gardens. The distances among host patches can programs (Averill 1985). vary considerably as might the optimal foraging pat- In this long-termstudy, we have begun to describe terns that would best exploit the oviposition oppor- patterns of fruit ßy resource use by determining spatial tunities (Aluja and Prokopy 1992, Aluja and Birke and temporal variation in the distributions of larvae of 1993). On a smaller (micro) level, a ßy must deal with Anastrepha obliqua (Macquart), A. striata, A. frater- variance within the tree itself given that the distribu- culus, and Anastrepha alveata Stone within the cano- tions of fruit and favorable microhabitats within the pies of single representatives of their wild host trees in canopy may not be homogeneous. Uneven distribu- Veracruz, Mexico: Spondias mombin L. (Anacardi- tions of a number of frugivorous insects, including aceae), Psidium guajava L. and Psidium sartorianum adult tephritids and the immature parasitoids of Te- (Berg.) Ndzu. (Myrtaceae), and Ximenia americana phritidae, within canopies sometimes reßect this vari- (Olacaceae), respectively. In the process we employ ability (Strong and Levin 1979, Aluja and Birke 1993, a novel statistical method, the two-level hierarchal Sivinski et al. 1997, Aluja et al. 2000). Some of the regression model, to better ascertain the role that important components of microhabitat variance from fruiting phenology considered here to be fruit avail- an insectÕs perspective are temperature, solar radia- ability and fruit size considered here to be host quality tion, and relative humidity (Hedstro¨m1992). Similar play in determining spatial distributions. Studies were factors may also inßuence the distribution of fruits, carried out over 6 yr in the P. guajava tree, 5 yr in the and hence the distribution of ovipositing females and S. mombin and X. americana trees, and 4 yr in P. their offspring (Messina 1989). sartorianum trees. A. obliqua, A. striata, and to some Host availability generates the second type of re- extent A. fraterculus are considered of economic im- source variance. Typically, fruit ßy hosts have distinct portance in Mexico due to the damage they cause in fruiting seasons. The resource is only available for a mango, Mangifera indica L., and guava, P. guajava short period, although the degree of ephemerality (Herna´ndez-Ortõ´z and Aluja 1993, Aluja 1994). In con- varies greatly among tree species (Aluja and Birke trast, A. alveata attacks the fruit of a single wild tree 1993). Wild hosts are often more ephemeral than cul- species, X. americana, and is of no agricultural signif- tivated species, which have been selected to bear icance (Piedra et al.1993). In addition, the abundances fruits over an extended season (van Schaik et al. 1993). of A. striata and A. fraterculus in P. guajava along an Further temporal variance in host availability is added altitudinal transect (0Ð1,800 mabove sea level) were by the unpredictability of the fruiting season and determined, and the regional-scale patterns and their yearly differences in yield, which may be inßuenced environmental correlates were used to help interpret by climate (Herrera 1998). For example, the fruiting the within-canopy distributions of the ßies. of a highly seasonal fruit can be delayed by drought or low temperatures (Reuther 1973). Materials and Methods Finally, components of host quality, i.e., fruit size, color, and degree of ripeness, previous use by con- Study Sites. The study sites were in or near the speciÞcs and the concentration of deleterious allelo- villages of Tejerõ´a and Llano Grande in central Vera- chemicals, can all vary, some independently of the cruz State, Mexico. Tejerõ´a is located at 19Њ 22Ј N others (Dõ´az-Fleischer et al. 2000). Even though a fruit latitude and 96Њ 53Ј W longitude, at a mean altitude of might be of optimal quality based on some physical 1000 mabove sea level. Llano Grande is situated at 19 Њ character such as size, other factors such as stage of 22Ј N latitude and 96Њ 56Ј W longitude, and a mean ripeness or previous use could be detrimental to larval altitude of 950 m. Climates at both sites were semihot development (Fitt 1983). Host-marking pheromones, and humid (Soto 1986), and the environments were such as used by a number of Anastrepha spp., may act characterized by an abundance of wild