Allopatric populations of Drosophila ananassae exhibit different degree of trade-off for evolving immune response against bacterial infection

Abstract

Abstract We conducted laboratory based selection experiment with two allopatric populations of Drosophila ananassae collected from two isolated geographic regions of India namely, Mysuru and Port Blair and subsequently inbred for several generations at laboratory. The populations were infected enteritically with the bacteria Pseudomonas aeruginosa for fifty-five generations followed by ten generations under relaxed selection. We tested development of immune-competence of the selected flies through the generations and inquired if elicitation of immune responses were needed to pay cost by trading-off with life history and morphological traits. We observed gradual and progressive increase in longevity, reproductive life span, post reproductive life span, developmental time, fecundity rate, fat content and gradual reduction in body length and water content. Under relaxed selection regime there was a reversion of all the traits but not to the basal level. Responses exhibited by the infected-selected flies from Port Blair and Mysuru differed, with the former group exhibited more reduction in body length, more reduction in water content, greater antioxidant enzyme activity, longer post infection period, greater survival than later group. On other side, Mysuru flies showed greater fat deposition, faster developmental time, longer oviposition time than Port Blair flies. Interestingly, Port Blair flies exhibited, increase in post ovipository period in contrast to Mysuru flies that showed decrease for the same. We inferred that two allopatric populations of D. ananassae show different trade-off for evolving immune response with life history traits.