Abstract
We describe the gut bacterial diversity inhabiting two saprophagous syrphids and their breeding substrate (decayed tissues of the columnar cactus Isolatocereus dumortieri). We analyzed the gut microbiota of Copestylum latum (scooping larvae that feed on decayed cactus tissues) and Copestylum limbipenne (whose larvae can also feed on semiliquid tissues) using molecular techniques. DNA was extracted from larval guts and cactus tissues. The V1-V3 region of the 16S rRNA genes was amplified and sequenced. A total of 31079 sequences were obtained. The main findings are: C. limbipenne is dominated by several Enterobacteriaceae, including putative nitrogen-fixing genera and pectinolitic species and some denitrifying species, whereas in C. latum unclassified Gammaproteobacteria predominate. Decayed tissues have a dominant lactic acid bacterial community. The bacterial communities were more similar between larval species than between each larva and its breeding substrate. The results suggest that the gut bacterial community in these insects is not strongly affected by diet and must be dependent on other factors, such as vertical transmission, evolutionary history and host innate immunity.
Highlights
Copestylum is a neotropical endemic syrphid lineage that harbours one of the highest species richness, with over 400 species [1,2,3]
This study describes, for the first time, the bacterial diversity inhabiting in necrotic tissue of the columnar cacti Isolatocereus dumortieri and in the gut of two species of Copestylum by partial sequencing of 16S rRNA genes directly amplified from samples
Bacterial diversity and rarefaction analysis We were close to completeness of the bacterial inventory at family and genus level according to the rarefaction curves (Figure 2) and the Chao1 estimator of bacterial richness (Table 1)
Summary
Copestylum is a neotropical endemic syrphid lineage that harbours one of the highest species richness, with over 400 species [1,2,3]. Larvae of Copestylum Macquart 1986 (Diptera: Syrphidae) are commonly bred in decayed cactus species and assist in the degradation of cactus necroses contributing to recycling processes in xeric environments [6,7,8]. Besides their ecological importance, this group presents interesting feeding strategies: Rotheray et al found morphological differences among Copestylum larvae reared from Cactaceae [3]. The species that can feed on watery material (straining) have reduced armature and have an elongate posterior breathing tube. Examples of scooping species are C. latum and C. posticum; some straining species are C. mila and C. hidalgense, and the intermediate species are C. limbipenne and C. marginatum
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