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First records of Zaprionus indianus Gupta, 1970 (Diptera, Drosophilidae), a potential pest species, from Panama and the United States of America
Kim van der Linde, Jeffrey S. Birdsley, Linette M. Alonso, David Houle Department of Biological Science, Florida State University, Tallahassee, FL 32306-1100, USA; E-mail:
Zaprionus indianus Gupta, 1970 (Diptera, Drosophilidae), is native to Africa and its coastal islands, the Middle East (Israel and Saudi Arabia), southern Europe (Malta, Italy, Spain, and Austria) and southern Asia (Pakistan and India; see references in Chassagnard and Kraaijeveld, 1991; Bächli, 1999-2005). This species was first found in the Americas in 1998 when it was reported from São Paulo, Brazil (Vilela, 1999). Since then, it has spread rapidly through Brazil (Stein et al., 1999; Castro and Valente, 2001; De Toni et al., 2001; Santos et al., 2003; Tidon et al., 2003; Dobbin et al., 2004; Kato et al., 2004; da Silva et al., 2005) and neighboring Uruguay (Goní et al., 2001, 2002) and has been predicted to reach the USA in the near future (David et al., 2005). Here we report the first records of Z. indianus from Panama and the USA.
Zaprionus indianus is assigned to the subgenus Zaprionus, species group armatus and species subgroup vittiger (Chassagnard, 1988; Chassagnard and Tsacas, 1993). We provide here the diagnostic characters of this species and higher taxonomic levels because the published key (Chassagnard and Tsacas, 1993) is in French. The genera Zaprionus and Phorticella both have distinctive silvery-white stripes on the top of the head and the thorax.
The lobes of the epandrium are truncated in Phorticella but finger-like in Zaprionus, and the anterior orbital bristle is long in Zaprionus but short in Phorticella. Within genus Zaprionus, the subgenus Zaprionus has an even number of stripes across the thorax, whereas the
subgenus Anaprionus has an odd number of stripes. The species of the armatus group are characterized by fore femora that have either one large spine on a prominent tubercle (subgroup tuberculatus) or a series of large spines, whereas the species of the inermis group lacks these spines. The species of the vittiger subgroup, including Z. indianus, have 4 to 6 composite spines each of which has a second short branch at its base. These spines function as a rest for the tibia when the leg is folded. The species of the armatus subgroup have simple spines, whereas the species of the tuberculatus subgroup have a single long and prominent simple spine on a large tubercle. Within the vittiger subgroup, Z. indianus is identified by its overall yellowish (not brown) color and narrow (relative to those of the other species) silver bands bordered by black bands across the thorax and scutellum. The black bands do not widen on the scutellum, and the scutellum is without a white tip. The composite spines are not located on small tubercles as in some other species within the subgroup.
On 6 and 7 October 2003, DH collected several individuals of Z. indianus on Isla Contadora, Panama. On October 13, 2005, LMA collected a single female from Tom Brown Park, Tallahassee, Florida. On October 15, 2005, we collected about a dozen individuals near the Apalachicola Shooting Range, Forest Road 305, southwest of Tallahassee in the
Apalachicola National Forest. In each case, flies were netted off banana baits. We confirmed our identifications of these specimens as Z. indianus using published keys (Chassagnard, 1988; Chassagnard and Tsacas, 1993) and by direct comparison with alcohol-preserved material from a laboratory stock of Z. indianus provided by Dr. Jean David. We have since observed several individuals in an open-air vegetable store in the center of Tallahassee, Florida, and we now regularly find this species in our samples.
We are confident that these are very recent introductions for both countries, as we have collected flies in these same areas previously without detecting Zaprionus. KvdL
collected drosophilid flies along the Panama Canal across the Isthmus of Panama in June–July 1998 and April 2002 using oviposition traps baited with banana. JSB made weekly
collections on fruit and vegetable compost in Tallahassee from August 2000 to July 2005 and less frequently at other Tallahassee locations, including Tom Brown Park. We also
performed an extensive set of mark-release-recapture experiments with Drosophila at the Apalachicola National Forest site in 2000, 2003, and May 2005. JSB and DH have also made irregular collections of drosophilid flies across the southeastern U.S. since 2000 and, in far south Florida, as recently as March 2003. The distinctive appearance of the species makes it unlikely that experienced observers would fail to recognize it in a sample. The large number of collections made in countries north of Brazil since 1998 (Bächli, 1999-2005), when the first individuals were collected, and the absence of reports on this species in those collections underline the recent colonization by the species of the area north of Brazil.
The most likely scenario based on these observations is that this species has spread through Central America and the Caribbean and reached the USA in either 2004 or 2005. A second possibility is that these represent isolated introductions from elsewhere in the
Americas or the Old World. A possible source for the Tallahassee population is escape from a stock that we maintained in the laboratory during late 2003 and early 2004, but this scenario seems unlikely given our failure to observe the species locally between 2003 and October 2005, despite intensive collecting. The species is known to spread rapidly in newly colonized areas (Castro and Valente, 2001; Goní et al., 2001, 2002; Santos et al., 2003; Stein et al., 2003; Tidon et al., 2003; Dobbin et al., 2004; Kato et al., 2004; da Silva et al., 2005; David et al., 2005; Ferreira and Tidon, 2005). Vilela and coworkers (Vilela, 1999; Vilela et al., 2001) suggested that the species might have colonized Brazil from the USA, but that possibility is not substantiated by previous records in North America.
The appearance of this species may have agricultural implications, as it has been recorded as a pest species on oranges, peaches, and figs in Brazil (Stein et al., 1999, 2003;
Vilela, 1999; Vilela et al., 2001; Raga and de Souza Filho, 2003; Santos et al., 2003). Its breeding substrates are not limited to cultivated fruits (Santos et al., 2003), making it difficult to control. Tidon et al (2003) reported that this species lays eggs on fruits that are still
ripening, making the fruit unsuitable for human consumption.
Z. indianus has continued its spread in the New World and has now reached North America as predicted (David et al., 2005). We could document the arrival of this potential pest species in north Florida because of our extensive sampling efforts over past years.
Catching the arrival of a species offers a rare opportunity to study the dynamics of such an invasion in progress.
Individuals of this species collected in Tallahassee will be deposited at the American Museum of Natural History. Subcultures of the Tallahassee stock can be obtained from the authors and will be provided to the Tucson Drosophila Species Stock Center
Acknowledgements: We thank Jean David for providing the laboratory stock of Z.
indianus in 2003 and all our colleagues from Florida State University (Tallahassee) and University of Florida (Gainesville) who helped collect the flies in the Apalachicola National Forest. This work was supported by U.S. National Science Foundation grant DEB-0129219 to D. Houle.