Allopatric sibling species pair Drosophila nasuta nasuta and Drosophila nasuta albomicans exhibit expression divergence in ovarian transcriptomes

Drosophila nasuta nasuta and Drosophila nasuta albomicans represent cross fertile members of the immigrans species group of Drosophila with an allopatric mode of distribution exhibiting characteristic novelties. Illumina sequencing technology and de novo transcriptome assembling strategies were used for the current study. The analysis revealed 8% of the transcriptome to be differentially expressed between the ovaries of these two species, of which 9% was related to female reproduction. The majority of the differentially expressed genes were enriched for genetic information processing pathways, biosynthesis, and metabolism-related pathways. SNPs in D. n. albomicans transcriptome was double in number than in D. n. nasuta and only 5% of these SNPs were fixed. Ka/Ks ratios indicated the lineages were under strong purifying selection. The genes which are differentially expressed are evolving at a similar rate as that of genes with conserved expression. Thus, the current findings provide useful insights on the expression dynamics during incipient species divergence of D. n. nasuta and D. n. albomicans since their divergence time of similar to 0.5 million years.

Automated summary

The transcriptome analysis of Drosophila nasuta nasuta and Drosophila nasuta albomicans revealed 8% differential expression in ovaries, with 9% related to female reproduction. Most differentially expressed genes were enriched in genetic information processing pathways, biosynthesis, and metabolism-related pathways. D. n. albomicans had twice as many SNPs in its transcriptome compared to D. n. nasuta, with only 5% being fixed, indicating strong purifying selection on these lineages.