Drosophila bromeliae

Schmitz, Hermes José & Valente, Vera Lúcia da Silva, 2019, The flower flies and the unknown diversity of Drosophilidae (Diptera): a biodiversity inventory in the Brazilian fauna, Papéis Avulsos de Zoologia (Pap. Avulsos Zool., S. Paulo) 59, pp. 1-15 : 7-8

Drosophila bromeliae species group

This group showed to be the most speciose, abundant and widespread, found in all sites surveyed ( Fig. 1 ) and also the more taxonomically challenging.Altogether, eight species were found. All these species are cryptic with regard to external morphology but can be discriminated by aedeagus morphology. In the time of sampling, just five species of D. bromeliae species group were described,and descriptions of terminalia were not available for the two species described by Sturtevant (1916, 1921). This impeded the recognition if any of the species found were conspecific to Sturtevant’s species and, therefore, which of them represented new species. Just D. bromelioides specimens could be clearly recognized based on the male terminalia of the lectotype depicted by Val (1982).After Grimaldi (2016) redescribed the Sturtevant’s specimens, another of the species found in this survey could be recognized as D. bromeliae . The identity of the six other species found here deserves a more careful study since there are subtle to great differences in the morphology of aedeagus from all the other described species, including the nine new species described by Grimaldi (2016) based mostly on Central American specimens. They are mentioned herein as types III, III’, IV, IV’, V and VI.

The species found in the present survey showed marked differences in host species ( Table 1), from broad generalist to ecologically specialized species. Individuals of the polyphagous species started to emerge from flowers around 10‑13 days after the field collection. The Solanum ‑specialized species takes a little longer, around 13‑16 days.

Drosophila bromelioides was the most conspicuous species and proved to be widely generalist,recorded in42 host species, from 16 botanical families. Although rarely, this species is sometimes caught at low numbers even in banana‑baited traps (De Toni et al., 2007; Gottschalk et al., 2007; Schmitz et al., 2007) and under constant attention can be reared in a banana‑agar medium in the laboratory. However, flowers are clearly its preferred breeding site. It was found in southern localities, in the states of Rio Grande do Sul, Santa Catarina, Paraná, and São Paulo. Other studies have recorded it also in other south‑central Brazil localities ( Vilela & Mori, 1999; Chaves & Tidon, 2008; Roque & Tidon, 2008). A morphologically similar species, D. bromeliae , was found in northern Brazilian localities (Pará, Pernambuco and Mato Grosso states) in the present study and reported to Caribbean, Central America, and Ecuador by Grimaldi (2016). This is the first confirmed record of the species in Brazil. Although some earlier studies reported D. bromeliae or D. bromelioides in other localities, caution is needed, due to the cryptic diversity revealed here and by Grimaldi (2016). As ex‑ amples, there are records for D. bromeliae in Campos do Jordão (São Paulo) by Hsu (1949) and D. bromelioides in Salvador (Bahia) by Malogolowkin (1951). However, both precede the first description of aedeagus for D. bromelioides ( Val, 1982) and for D. bromeliae ( Grimaldi, 2016) , so, it is advisable to treat these and other cases as doubtful. Based on the results of the present survey, D. bromeliae is probably also a polyphagous species, found in five host species, of five families, and also can be reared in the banana‑agar medium. As our sampling effort in northern Brazilian regions was lower, these numbers cannot be directly compared to those of D. bromelioides . Future samplings in the region are necessary to clear the extent of the niche breadth of this species. It is probable that various other hosts can be found.

Based on aedeagus morphology, types III and III’ are thought to be closely related species. Type III was found in the southern states of Rio Grande do Sul and Santa Catarina,while the type III’ was found in the northeastern state of Pernambuco. Although also polyphagous, being found in six host species from five families, type III exploits a smaller variety of host plants compared to the sympatric D. bromelioides . In turn, the type III’ was found in only one host species, being more restricted than the sympatric species D.bromeliae . However,future sampling probably must find other host plants for it, since it was discovered breeding in Thunbergia grandiflora , which is a cultivated exotic plant. Presumably, it may occupy a similar niche to its southern sibling type III, i.e., polyphagous but not as generalist as D. bromelioides and D. bromeliae . Both types III and III’ can be reared, although not easily, in banana‑agar medium in laboratory.

In southern localities, D. bromelioides and type III can occur is some hosts both syntopically and synchronically, although seemingly with some different preferences. A great number of type III specimens were reared from Brugmansia suaveolens , where it generally outnumbered D. bromelioides . Ipomoea alba was an exception in its genus for apparently representing an important host for type III, whereas other species of the genus host almost exclusively D. bromelioides . The type III’ was also found co‑occurring with the more generalist D. bromeliae in Thunbergia grandiflora flowers in Pernambuco. All four species showed to be able to breed in some exotic plants.

In contrast to their more generalist siblings,four more specialized species complete the group,all of them exclusively using species of Solanum as host species. Despite some effort, none of these species could be reared in artificial culture media in laboratory, even when some kind of Solanum flower juice was added to the medium.These species are being called here as types IV, IV’, V and VI.

The types IV and IV’ are morphologically similar. Type IV was found in the southern states of Rio Grande do Sul and Santa Catarina, while the type IV’ was found in Bahia, Minas Gerais, São Paulo, Paraná, and Santa Catarina. Additionally, the type V was also found in the southern states of Rio Grande do Sul and Santa Catarina. These species share some hosts with type IV, although the two species seem to have some different host pref‑ erences. Both species breed in Solanum paniculatum , sometimes from the same plant; on the other hand, type IV occurs solely in S.mauritianum , while type V is the only found in S. sisymbriifolium in these localities. Other Solanum species were less sampled, but both fly species shared S. sanctaecatharinae . The type V showed to have a slightly wider niche, being found in six species of Solanum , while type IV was found in three species. Some specimens of the generalist D. bromelioides were reared from Solanum flowers, but only in a few occasions and at low numbers, suggesting that this genus does not represent a main host for it. Finally, in a sample taken in the northern state of Pará, another species was found, the type VI. Its host plant, S. stramoniifolium does not occur in southern Brazil.

Solanum is a large and worldwide distributed genus, especially in tropical and subtropical regions ( Mentz & Oliveira,2004). Species sampled in the present survey are native from Neotropics and are mostly ruderal plants,occurring on pioneer types of vegetation, at roadsides, field and forest borders. However, no equivalent Solanum ‑ specialized drosophilid is known in other parts of the world. The only literature record known by us is on the occurrence of Scaptodrosophila minimeta (Bock) in flowers of S. torvum and S. mauritianum in Australia (Bock & Parson, 1981), but the ecology of this species is poorly known. It can be inferred that this species uses other natural resources, as both species of Solanum are native from the Neotropics and introduced to Australia.

The records presented here suggest the existence of pairs of morphologically and ecologically similar species in different localities in Brazil, in each case with one of them found in northern localities and another in southern localities (the generalist D. bromeliae and D. bromelioides , the oligophagous types III’ and III, the Solanum ‑ specialized types IV’ and IV, respectively with a northern and a southern distribution).Though, since our sampling in the huge Brazilian territory and plant biodiversity was not exhaustive and was biased to southern localities, this preliminary observation needs to be tested by future studies.

Figures

Figure1.MapofBrazilshowingthestatesandmunicipalitieswherenewsamples for this study were taken: RS = Rio Grande do Sul:(1) Pelotas, (2) Porto Alegre,(3) Caxias do Sul,(4) Flores da Cunha;SC = Santa Catarina:(5) Antônio Carlos, (6) Florianópolis, (7) Governador Celso Ramos; PR = Paraná: (8) São Josédos Pinhais,(9)Guarapuava;SP =SãoPaulo:(10)Águasde Lindóia;MG= Minas Gerais:(11) Monte Sião;BA = Bahia:(12) Itaparica;PE = Pernambuco: (13)Vitória de Santo Antão,(14) Recife;PA = Pará:(15) Belém.