Abstract
Brazilian fauna of drosophilids has been researched in various ecosystems, but those in mangrove forests remain overlooked in Brazil and elsewhere. The present study attempts to characterise the assemblages of drosophilids of this environment, based on 28 collections taken in three mangrove areas in Santa Catarina Island, southern Brazil. The three mangroves surveyed were different in their surroundings, which varied from highly urbanised areas to conservation areas with natural vegetation. Overall, 69 species were collected, and no remarkable difference was detected in species composition and abundances or in the richness, evenness and heterogeneity between sites. The species abundance distribution observed fitted to a theoretical lognormal distribution in the three mangroves. The species richness scored and the performance of the species richness estimators showed an unexpectedly high diversity, considering the very low floristic diversity and the harsh conditions of the environment. Regarding species composition and abundances, the drosophilid mangrove assemblages were shown to be more similar to those found in open environments, with a marked dominance of exotic species. Finally, considering the apparent lack of feeding and breeding sites, we suggest that mangrove forests are acting as sink habitats for the drosophilids populations.
Highlights
We considered two alternative hypotheses: (1) species abundances and diversity measures of mangrove drosophilid assemblages respond to the differences in the environments surrounding the mangroves; and (2) mangrove forests of the same region have typical drosophilid assemblages, not showing differences in species abundances and diversity measures, despite differences in the surrounding environments
A total of 82,942 drosophilids were collected in the 28 samples taken in the three mangrove forests of Santa Catarina Island (Itacorubi: N=32,800, Sobs=51, n=13; Rio Tavares: N=24,804, Sobs=48, n=8; Ratones: N=25,338, Sobs=45, n=7)
The following species were tested for possible differences in absolute abundance between sites: D. ananassae Doleschall, 1858, D. melanogaster Meigen, 1830, D. malerkotliana, D. simulans, D. capricorni Dobzhansky & Pavan, 1943, D. nebulosa Sturtevant, 1916, D. paulistorum, D. willistoni, D. sturtevanti Duda, 1927, D. hydei Sturtevant, 1921, D. mercatorum, D. repleta, D. neocardini Streisinger, 1946, D. polymorpha, D. griseolineata Duda, 1927, D. mediostriata, D. pallidipennis Dobzhansky & Pavan, 1943, D. caponei Pavan & da Cunha, 1947 and Z. indianus
Summary
Our main objectives were: (1) to characterise the species abundances and diversity measures of mangrove drosophilid assemblages, and (2) to investigate their spatial variation, considering mangrove forests located in the same region but differing in their surroundings. A total of 82,942 drosophilids were collected in the 28 samples taken in the three mangrove forests of Santa Catarina Island (Itacorubi: N=32,800, Sobs=51, n=13; Rio Tavares: N=24,804, Sobs=48, n=8; Ratones: N=25,338, Sobs=45, n=7).
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