A New Species of Drosophila ( Diptera : Drosophilidae ) from the Inflorescences of Xanthosoma sagittifolium ( Araceae )

A new species of the genus Drosophila, Drosophila sagittifolii sp. nov. is described. Adult specimens of D. sagittifolii were aspirated from the inflorescences of Xanthosoma sagittifolium (L.) Schott (camacho), from which they also emerged, at the Río Guajalito Research Station, Santo Domingo de los Tsáchilas, Ecuador.


INTRODUCTION
In Ecuador, most collections of Drosophila use fruit-baited traps to study fruit flies, and for this reason little is known about the ecology of flower-breeding and feeding Drosophila species.However, some Ecuadorian species from the followings species groups: Drosophila flavopilosa Frey, 1919, Drosophila bromeliae Sturtevant, 1921, Drosophila onychophora Vilela & Bächli, 1990 and Drosophila morelia Vilela, 2004 have been found living in flowers of the botanical families Solanaceae, Bromeliaceae and Asteraceae (Silva and Martins 2004, Vilela and Bachli 2004, Figuero and Rafael 2011, Figuero et al. 2012, Robe et al. 2014).In particular, interactions like reproductive ecology between species of Araceae and flies have been observed (Gibernau 2003, Miyake andYafuso 2005).Specifically, species of the genus Colocasiomyia (Diptera:Drosophilidae) are found on inflorescences of the Araceae genus, Alocasia, Colocasia and Homalonema (Miyake and Yafuso 2005).Furthermore, Tsacas and Chassagnard (1992) suggests the existence of a close association between Xanthosoma robustum of the Araceae family and Drosophila aracea.The aforementioned relationship is likely to occur in Ecuadorian areas where low altitude and high humidity produce a high species richness of Araceae (Leimbeck et al. 2004).Xanthosoma, an abundant Araceae terrestrial herb, is a genus whose inflorescences provide shelter to communities of arthropods (García-Robledo et al. 2004).Moreover, the plants of Xanthosoma sagittifolium are commonly cultivated in the American tropics because their tubers are used as food (Missouri Botanical Garden 2017).Its inflorescence is made up of a spadix and a sphate: the spadix has pistillate flowers at the base, sterile flowers in the middle, and staminate flowers in the upper part (García-Robledo et al. 2004, Takano et al. 2012).This paper describes a new species of Drosophila associated with the inflorescence of Xanthosoma sagittifolium (L.) Schott (camacho) (Araceae).
Collections were made during six nonconsecutive months (September 2010, March, June, July, August and September 2011).Adult specimens of Drosophila were collected directly from the inflorescences of Anthurium spp.and Xanthosoma sagittifolium (Figure 1) using an entomological aspirator.Several inflorescences were also collected with the possibility that they contained eggs and larvae.These inflorescences were kept in the laboratory in glass jars with moist paper until emergence of the imagines.
Abdomen.-(Figure 3) Yellow; tergite 1 yellow, tergite 2 with dorsal midline and triangular dark pigmentation; tergite 3 without dorsal midline, with hourglass-shape pigmentation that extends laterally to the margin; tergite 4 without dorsal midline, with a tenuous stripe near the edge and a dark stripe on the posterior edge; tergite 5 yellow with a dark line along the posterior edge; tergite 6 yellow (in some females, area around the abdomen may be slightly darker).Length (Body + wings Egg.-Oval-shaped with four long, curved filaments.
Etymology.-Thisspecies is named in recognition of its presumed primary larval host plant, Xanthosoma sagittifolium.
Biology.-Adults of D. sagittifolii sp.nov.were found only on Xanthosoma sagittifolium inflorescences at the Río Guajalito Research Station.Eleven individuals (four males and seven females) emerged in the laboratory from three inflorescences of X. sagittifolium after 36 days in laboratory.
belongs to the genus Drosophila.Judging by the shape of the aedeagus, D. sagittifolii sp.nov.could be related to Drosophila crassa, Patterson & Mainland, 1944 an ungrouped species (Vilela and Bächli 1990) It is also similar to the aedeagus of the Drosophila canalinea group of species, such as Drosophila annulosa Vilela & Bachli, 1990 and Drosophila parannularis, Vilela & Bachli, 1990.Although the collections of Drosophila adults were from inflorescences of Anthurium spp.and X. sagittifolium, Drosophila sagittifolii sp.nov.adults were only found from the X. sagittifolium inflorescences.The natural breeding and larval feeding sites of the species in relation to flowers have not been studied sufficiently.Drosophila saggitifolii sp.nov. is not attracted to traps baited with fermented banana.This fact has been corroborated simultaneously in the same place and at the same time, 3 369 flies from 26 species of Drosophila were captured using banana baits fermented with baker's yeast, and no D. sagittifolii sp.nov.were found (Cabezas 2012).
During these collections of D. sagittifolii sp.nov. on the inflorescences of X. sagittifolium, three couples in copulation were captured and individuals of the new species emerged from the inflorescences in the laboratory.This suggests that X. sagittifolium is one of the natural breeding and courting sites used by D. sagittifolii sp.nov.
The determination of the natural feeding and breeding sites of species in the Drosophilidae family is not an easy task.The abundance and frequency of the hosts/substrates used and the existing faunal associations must be understood.Climatic and geographic factors will also play a role in determining seasonality and range of these species (Brncic 1983).Therefore, it is necessary to continue to conduct phylogenetic, ecological and geographical studies of both the Drosophila species and its presumed host plant, Xanthosoma sagittifolium, to establish the true interaction between the insect and the inflorescences.