Sex-specific ultraviolet radiation tolerance across Drosophila.

ABSTRACT

The genetic basis of phenotypic differences between species is among the most longstanding questions in evolutionary biology. How new genes form and the processes selection acts to produce differences across species are fundamental to understand how species persist and evolve in an ever-changing environment. Adaptation and genetic innovation arise in the genome by a variety of sources. Functional genomics requires both intrinsic genetic discoveries, as well as empirical testing to observe adaptation between lineages. Here we explore two species of Drosophila on the island of Sao Tome and mainland Africa, D. santomea and D. yakuba. These two species both inhabit the island, but occupy differing species distributions based on elevation, with D. yakuba also having populations on mainland Africa. Intrinsic evidence shows genes between species may have a role in adaptation to higher UV tolerance with DNA repair mechanisms (PARP) and resistance to humeral stress lethal effects (Victoria). We conducted empirical assays between island D. santomea, D. yakuba, and mainland D. yakuba. Flies were shocked with UVB radiation (@ 302 nm) at 1650-1990 mW/cm2 for 30 minutes on a transilluminator apparatus. Custom 5-wall acrylic enclosures were constructed for viewing and containment of flies. All assays were filmed. Island groups did show significant differences between fall-time under UV stress and recovery time post-UV stress test between regions and sex. This study shows evidence that mainland flies are less resistant to UV radiation than their island counterparts. Further work exploring the genetic basis for UV tolerance will be conducted from empirical assays. Understanding the mechanisms and processes that promote adaptation and testing extrinsic traits within the context of the genome is crucially important to understand evolutionary machinery.