Abundance and Richness of Cryptic Species of theWillistoniGroup ofDrosophila(Diptera: Drosophilidae) in the Biomes Caatinga and Atlantic Forest, Northeastern Brazil

Abstract

Cryptic species meet the biological definition of species, but are morphologically identical or quite similar. Several ecological studies underestimate richness and neglect important information on cryptic species, as they are rather difficult to identify. Among insects, drosophilids of the willistoni subgroup, which includes Drosophila willistoni Sturtevant, Drosophila paulistorum Dobzhansky & Pavan, Drosophila equinoxialis Dobzhansky, Drosophila tropicalis Burla & da Cunha, Drosophila insularis Dobzhansky, and Drosophila pavlovskiana Kastritsis & Dobzhansky, are good examples of cryptic species. Although several studies have shown that this subgroup is one of the most abundant in the Neotropical region, no identification to species level has been reported for areas where these individuals live in sympatry. This study evaluates the seasonal oscillations in abundance of this subgroup in biomes with contrasting vegetation and rainfall regimes: the Caatinga and the Atlantic Forest, in northeastern Brazil. Approximately 39,000 drosophilids were captured in 24 collections, of which 18,000 belonged to the willistoni subgroup. The most abundant were D. willistoni, D. paulistorum, and D. equinoxialis, in this order. D. equinoxialis was recorded in only one of the environments surveyed, represented by few individuals. In all environments, individuals of the willistoni subgroup were more abundant in the rainy season, when richness often was higher. The results underline the importance of humidity and of temperature for the subgroup willistoni and indicate the ecological versatility of some of its species.

Effects of seasonality on drosophilids (Insecta, Diptera) in the northern part of the Atlantic Forest, Brazil

“…In a study about the first subgroup, Garcia et al . (2014) had already observed the identical seasonal pattern in other fragments in the northern Atlantic Forest, which has also been reported for the southern part of the biome (Dobzhansky & Pavan 1950; Franck & Valente, 1985; Tidon-Sklorz & Sene, 1992; Saavedra et al ., 1995; De Toni et al ., 2007; Garcia et al ., 2012). Dobzhansky (1957) and Spassky et al .…”

“…The greater abundance of Neotropical species in the rainy season may be attributed mainly to species of the willistoni (D. willistoni and D. paulistorum) and of the saltans (D. sturtevanti and D. prosaltans) subgroups. In a study about the first subgroup, Garcia et al (2014) had already observed the identical seasonal pattern in other fragments in the northern Atlantic Forest, which has also been reported for the southern part of the biome (Dobzhansky & Pavan 1950;Franck & Valente, 1985;Tidon-Sklorz & Sene, 1992;Saavedra et al, 1995;De Toni et al, 2007;Garcia et al, 2012). Dobzhansky (1957) and Spassky et al (1971) highlight the fact that humidity is a limiting factor for these species, which may explain their higher abundance values in the rainy season.…”

“…The average number of drosophilids captured per trap was similar to the values recorded in the northern Atlantic Forest (Garcia et al ., 2014; Monteiro et al ., 2016) and higher compared with studies carried out in the southern part of the biome (Gottschalk et al ., 2007; Döge et al ., 2008; Cavasini et al ., 2014). Richness values were near those observed in other parts of the Atlantic Forest (De Toni & Hofmann, 1995; Garcia et al ., 2008; Penariol & Madi-Ravazzi, 2013).…”

Fruit‐breeding drosophilids (Diptera) in the Neotropics: playing the field and specialising in generalism?

“…The species with the greatest resource breadth were: D. simulans (90 plant taxa), D. nebulosa (57), Z. indianus (44), D. willistoni (43), D. melanogaster, and D. polymorpha (both 42). Several studies did not completely discriminate between sibling species, particularly in the D. willistoni subgroup (D. willistoni, D. paulistorum, D. equinoxialis and D. tropicalis), but when identifications were made, D. willistoni was usually the most common (Spassky et al, 1971;Garcia et al, 2014;Roque et al, 2017). If D. willistoni is assumed to be present in all references where the identification was incomplete, the number of plant species used by this drosophilid would be 114, the broadest niche breadth of all species reported.…”

Identification key for drosophilid species (Diptera, Drosophilidae) exotic to the Neotropical Region and occurring in Brazil

“…In Brazil, drosophilid communities have been studied by several independent research groups, covering the Amazonian and Atlantic forests (Medeiros and Klaczko, 2004;Penariol and Madi-Ravazzi, 2013;Coutinho-Silva et al, 2017;Santa-Brígida et al, 2017), the Cerrado biome (Tidon, 2006;Blauth and Gottschalk, 2007), Caatinga (Rohde et al, 2010;Garcia et al, 2014;Oliveira et al, 2016), araucarias (Cavasini et al, 2014), pampas (Poppe et al, 2016) and urban sites (Ferreira and Tidon, 2005;Gottschalk et al, 2007). Exotic species are recorded in all drosophilid assemblages, and their relative abundance depends on many factors, as vegetation type, the season of the year, and disturbance (Mata et al, 2015).…”