Long-term laboratory Drosophila populations show flexible plasticity in response to ancestral nutritional cues

Plasticity can help populations cope with environmental changes, namely by exploring various ecological niches. Addressing plasticity for nutritional responses in a range of fruit hosts potentially used by Drosophila may be essential in predicting the capacity of insects to colonize new environments or return to ancestral ones. Here, we test for differences in oviposition performance, reproductive success and juvenile viability in diverse host fruits in the colonizing species Drosophila subobscura (Collin 1936, Diptera: Drosophilidae) and compare them with those of the laboratory maintenance medium to which populations adapted for ~150 generations. We question as follows: Does D. subobscura show plasticity associated with various fruit hosts? Is performance better in the long-term maintenance (control) medium? We observed a higher fecundity, reproductive success and juvenile viability of flies maintained in the fruit media versus the control, but no differences between fruits. Our experiment shows that long-term laboratory populations of D. subobscura can still assess environmental cues of new substrates, allowing for flexible adaptive plasticity to occur through increased fecundity and reproductive success in fruit hosts relative to the control conditions. Importantly, this ability was not lost during long-term evolution in a benign, homogeneous environment. Furthermore, the high performance across fruits reinforces its status as a generalist species and further attests to its potential to colonize various ecological settings.