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Abstract Horizontal transfer of genetic material in eukaryotes has rarely been documented over short evolutionary timescales. Here, we show that two retrotransposons,ShellderandSpoink, invaded the genomes of multiple species of themelanogastersubgroup within the last 50 years. Through horizontal transfer,Spoinkspread inD. melanogasterduring the 1980s, while bothShellderandSpoinkinvadedD. simulansin the 1990s. Possibly following hybridization,D. simulansinfected the island endemic speciesD. mauritiana(Mauritius) andD. sechellia(Seychelles) with both TEs after 1995. In the same approximate time-frame,Shellderalso invadedD. teissieri, a species confined to sub-Saharan Africa. We find that the donors ofShellderandSpoinkare likely AmericanDrosophilaspecies from thewillistoni,cardini, andrepletagroups. Thus, the described cascade of TE invasions could only become feasible afterD. melanogasterandD. simulansextended their distributions into the Americas 200 years ago, likely aided by human activity. Our work reveals that cascades of TE invasions, likely initiated by human-mediated range expansions, could have an impact on the genomic and phenotypic evolution of geographically dispersed species. Within a few decades, TEs could invade many species, including island endemics, with distributions very distant from the donor of the TE.
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Evolution of compound eye morphology underlies differences in vision between closely related Drosophila species
Abstract BackgroundInsects have evolved complex visual systems and display an astonishing range of adaptations for diverse ecological niches. Species ofDrosophila melanogastersubgroup exhibit extensive intra- and interspecific differences in compound eye size. These differences provide an excellent opportunity to better understand variation in insect eye structure and the impact on vision. Here we further explored the difference in eye size betweenD. mauritianaand its sibling speciesD. simulans. ResultsWe confirmed thatD. mauritianahave rapidly evolved larger eyes as a result of more and wider ommatidia thanD. simulanssince they recently diverged approximately 240,000 years ago. The functional impact of eye size, and specifically ommatidia size, is often only estimated based on the rigid surface morphology of the compound eye. Therefore, we used 3D synchrotron radiation tomography to measure optical parameters in 3D, predict optical capacity, and compare the modelled vision to in vivo optomotor responses. Our optical models predicted higher contrast sensitivity forD. mauritiana, which we verified by presenting sinusoidal gratings to tethered flies in a flight arena. Similarly, we confirmed the higher spatial acuity predicted forDrosophila simulanswith smaller ommatidia and found evidence for higher temporal resolution. ConclusionsOur study demonstrates that even subtle differences in ommatidia size between closely relatedDrosophilaspecies can impact the vision of these insects. Therefore, further comparative studies of intra- and interspecific variation in eye morphology and the consequences for vision among otherDrosophilaspecies, other dipterans and other insects are needed to better understand compound eye structure–function and how the diversification of eye size, shape, and function has helped insects to adapt to the vast range of ecological niches.
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- Award ID(s):
- 1750833
- PAR ID:
- 10496064
- Publisher / Repository:
- Springer Science + Business Media
- Date Published:
- Journal Name:
- BMC Biology
- Volume:
- 22
- Issue:
- 1
- ISSN:
- 1741-7007
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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