No abstract

Within Drosophilidae, the Zygothrica genus group corresponds to a speciose mycophagous group, which remains insufficiently investigated despite its potential for ecological and evolutionary studies. The recognised gap in the knowledge of species diversity and the threat provided by global warming due to niche conservatism and stringent temperature and humidity requirements make this group an excellent candidate for testing the implementation of DNA barcoding, which is the aim of this study. Extensive prospecting in various parts of Brazil provided 220 specimens. Considering both the morphological and molecular results, these individuals consisted of 56 species that could be distributed into three categories: 22 corresponded to previously described species, 24 very likely corresponded to undescribed species, and 10 uncertain cases corresponded mainly to one or a few females. Intra‐specific distances ranged from 0% to 5.3%, whereas inter‐specific congeneric and inter‐generic distances ranged from 2.4% to 21.7% and from 7.4% to 20% respectively. Moreover, all species were revealed as reciprocally monophyletic and presented positive barcoding gap values; 62.5% of them presented diagnostic characters. Although coalescent‐based methodologies suggested some additional splitting, species initially considered to be different were never lumped together. Therefore, in general, DNA barcoding of mycophagous drosophilids provided results that are largely congruent throughout different molecular approaches and also with morphological boundaries. Several putative new species were revealed, highlighting the potential of cytochrome c oxidase subunit I (COI) barcodes as a tool complementary to traditional taxonomy in unravelling cryptic diversity among Neotropical mycophagous drosophilids.

In this paper we describe a new Zygothrica species that is morphologically, ecologically and evolutionarily related to Zygothrica vittimaculosa through molecular and morphological analyses. Moreover, we compare distribution, abiotic and biotic niches between both species and perform ecological simulations in order to assess the potential influence played by ecology versus geography in the divergence of the target species, which was also dated with the use of a nuclear marker. The aedeagus and wing morphometry patterns were underpinned by molecular evidence, as obtained for the mitochondrial COI and COII partitions. In fact, reciprocal monophyly and a barcoding gap were detected, in spite of the strict external resemblance, the strong abiotic and biotic niche overlaps and the frequent sympatry and syntopy observed between both species. Thus, we hypothesize here a mechanism of geographic speciation associated with a pattern of niche conservatism to the pair of Zygothrica species diverged at the Pliocene.

Understanding the mechanisms that shape the architecture, diversity and adaptations of genomes and their ecological and genetic interfaces is of utmost importance to understand biological evolution. Transposable elements (TEs) play an important role in genome evolution, due to their ability to transpose within and between genomes, providing sites of non-allelic recombination. Here we investigate patterns and processes of TE driven genome evolution associated with niche diversification. Specifically, we compared TE content, TE landscapes, and frequency of horizontal transposon transfers (HTTs) across genomes of flower-breeding Drosophila (FBD) with different levels of specialization on flowers. Further, we investigated whether niche breadth, and ecological and geographical overlaps are associated with potential for HTT rates. Landscape analysis evidenced a general phylogenetic pattern, in which species of the D. bromeliae group presented L-shaped curves, indicating recent transposition bursts, whereas D. lutzii showed a bimodal pattern. The great frequency of highly similar sequences recovered for all FBD suggests that these species probably experienced similar ecological pressures and evolutionary histories that contributed to the diversification of their mobilomes. Likewise, the richness of TEs superfamilies also appear to be associated with ecological traits. Furthermore, the two more widespread species, the specialist D. incompta and the generalist D. lutzii, presented the highest frequency of HTT events. Our analyses also revealed that HTT opportunities are positively influenced by abiotic niche overlap but are not associated with phylogenetic relationships or niche breadth. This suggests the existence of intermediate vectors promoting HTTs between species that do not necessarily present overlapping biotic niches.