First record of Zaprionus indianus Gupta, 1970 (Diptera, Drosophilidae) in southern localities of Uruguay.

 

Goñi, B., P. Fresia, M. Calviño, M.J. Ferreiro, V.L.S. Valente* and L. Basso da Silva*. Facultad de Ciencias, Instituto de Biología, Sección Genética Evolutiva, Universidad de la República, Igua 4225, Montevideo 11400, Uruguay. E-mail: bgoni@fcien.edu.uy.  *Departamento de Genética, Instituto de Biociências, Universidade Federal do Rio Grande do Sul, Caixa Postal 15053, 91501-970 Porto Alegre, RS, Brasil.

As part of a collaborative research project, we have been performing regular field collection of drosophilids in several localities from Uruguay with the aim to contribute to the knowledge of Neotropical fauna. Part of the data recorded up to now on Drosophila fauna of this region was published elsewhere (Goñi and Martinez, 1995;  Goñi et al., 1997, 1998). Here, we present three years collection data of drosophilids recorded in several southern localities of Uruguay with reference to the first register of occurrence of Zaprionus indianus Gupta 1970 (Diptera, Drosophilidae), and to some ecological considerations.

The genus Zaprionus, Coquillet, 1901 is composed by two subgenus with 57 species (Chassagnard and Kraaijeveld, 1991;  Chassagnard and Tsacas, 1993, reviewed by Vilela et al.,  2001).  They inhabit mainly in the Australasian, Afrotropical, Oriental and Palearctic biogeographical regions.  The origin of this species is supposedly found in the Afrotropical region, and it has recently been introduced in the American continent.  It was first registered in Brazil in March, 1999, in a sample of flies collected over persimmon fruits (Diospyrus kaky L., Ebenaceae) in Santa Isabel county, the State of São Paulo, Brazil (Vilela, 1999).  In December of the same year, Z. indianus was found in the State of Santa Catarina, Southern Brazil (De Toni et al., 2001).  Later, in March 2000, it was collected in the city of Porto Alegre, in the State of Rio Grande do Sul, the southernmost state of Brazil (see Castro and Valente, this issue).  This species was also recorded in several Brazilian states adjacent to the São Paulo State (Stein and Teixeira, 2000).  Z. indianus was found to be associated to several kinds of fruits belonging to both native and exotic species to the American continent (De Toni et al., 2001;  Vilela et al. 2001;  Castro and Valente, this issue).  It was also attracted to banana baits (De Toni et al., 2001).

Z. indianus is a generalist drosophilid species (Chassagnard and Kraaijeveld, 1991) and the only member of the genus which seems to be dispersing through the tropics, probably due to an intensification in fruits trade in the world (Vilela, 1999).  This species gained the status as pest, since it caused a loss on the production and exportation of figs (Ficus carica var. roxo-de-valinhos) of the 1999 harvest (around 40% and 80% losses, respectively) in the area of Valinhos the State of São Paulo and thus striking local economy (Stein and Teixeira, 2000, Vilela et al. 2001).  The commercialisation and transport of the infected fig production to different Brazilian states, mainly by the supermarket trade network, could have facilitated the fast dispersal of this fly.

Adults flies of this species are easily distinguishable from Neotropical drosophilids, since they show a pair of distinctive silvery-white stripes along the submedian area of the dorsal surface of the head and the thorax flanked by thin black stripes, a trait not found in the Neotropical species of drosophilids (Vilela, 1999).

 

 

We have collected drosophilids in three different regions from Uruguay (Table 1) dating from April 1999 to May 2001.  Depending on the substrates availability, adult flies were caught on rotting fruits and/or banana baits to obtain data on adult feeding sites (Table 1).  Moreover, fruits of both exotic and native plants were collected to obtain data on larval breeding sites (Table 1).  A detailed description of the methodological procedures is found in Goñi et al. (1998).

 

We collected 24,837 flies during the whole period of study (Goñi et al., unpublished data).  It included species members of the Drosophila and the Zaprionus genera, the species Zaprionus indianus being the only representive of the latter genus.  Table 2 indicates the number and the relative frequency of Z. indianus in relation to a given sample and the related substrate used as feeding and/or breeding site.  Z. indianus was found  for  the  first time in  Uruguay  in  April 2000,  emerging  from  fruits of  Butia yatai  (native species, see Table 2) collected in the Facultad de Agronomia, Montevideo.  In the same place, Z. indianus emerged from sampled fruits of Gingko biloba (exotic) in May 2001.  Moreover, we collected this species on fruits of Psidium guayava (native) in May 2000 at Santa Lucía, and on Butia capitata (native) and on banana baited trap, in the localities I and III, respectively, at the Rocha's wetlands, May 2000.  In all cases, Z. indianus was found in very low frequency, ranging from 0.05% to 3.28%.

It is worth mentioning that Z. indianus was absent in the samples collected at the native forest (locality II of Rocha's wetlands at about 10 km and 3 km apart from the localities I and III, respectively, see Table 1).  Our data indicate that Z. indianus was collected at partially man-disturbed environments referred to as urban or suburban in Table 1, which could ease the colonization of non-native drosophilids.  In Brazil, it seems that Z. indianus has successfully colonized urban areas of Porto Alegre city (Castro and Valente, this issue) being recorded in almost all samples in autumn and summer.  On the other hand, we have showed that Z. indianus is able to breed on native fruits and, therefore, able to invade natural environments and to compete for natural resources with, among others, native or cosmopolitan species of Drosophila.

While Z. indianus reaches relative frequencies as high as 45% in Southern Brazil  (De Toni et al., 2001;  Castro and Valente, this issue), it is found in very low frequency at the surveyed Uruguayan localities.  Further studies should be performed to monitor the course of Z. indianus colonization and its relation to biotic (for instance, breeding sites) and abiotic factors (like temperature) in this temperate region of South America.  Without doubt, Z. indianus constitutes an invaluable material to investigate the genetic strategy of a colonizer species.

 

Acknowledgments:  This work was partly supported by the grants from the Comisión Sectorial de Investigación Científica (CSIC) de la Universidad de la República to BG and LBS.

References: Castro, F., and V.L.S. Valente 2001, Dros. Inf. Serv. (this issue);  Chassagnard, M.Th., and A.R. Kraaijeveld 1991, Ann. Soc. Entomol. Fr. (N.S.) 27(4): 495-496;   Chassagnard, M.Th., and L. Tsacas 1993, Ann. Soc. Entomol. Fr. (N.S.) 29(2): 173-174;  De Toni, D., P.R.P. Hofmann, and V.L.S. Valente 2001, Biotemas 14(1): 71-85;  Goñi, B., and M.E. Martinez 1995, Dros. Inf. Serv. 76: 164;  Goñi, B., M.E. Martinez, and P. Daguere 1997, Revta. bras. Ent. 41(1): 89-93;  Goñi, B., M.E. Martinez, V.L.S. Valente, and C.R. Vilela 1998, Revta. bras. Ent. 42: 131-140;  Stein, C.P., and E.P. Teixeira 2000,  XXI Int. Congr. Ent., vol. I, p. 297;  Vilela, C.R., 1999, Dros. Inf. Serv. 82: 37-39;  Vilela, C.R., E.P. Teixeira, and C.P. Stein 2001, in: Histórico e impacto das pragas introduzidas no Brasil (Vilela, E.F., R.A. Zucci, and F. Canton, ed.) Chapter 7, pp. 48-52, Holos, São Paulo, Brazil.