Males can discriminate between females of different species, in part, by detecting differences in the hydrocarbon pheromones coating their bodies. Females can discriminate between males of different species, in part, by detecting species-specific differences in the male's courtship behavior. When copulation does occur between different species, the hybrid progeny are often non-viable, sterile or fertile with lower fitness.
The species of the simulans complex form a hard polytomy. Most likely, the island species D. (S.) mauritiana (Mauritius) and D. (S.) sechellia (Seychelles) branched off from the mainland species D. (S.) simulans in such a narrow time frame that it is impossible to distinguish which species branched off first and which second.
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