Parkash Ravi, Singh Shama, Ramniwas Seema
Department of Biochemistry and Genetics, Maharshi Dayanand University, Rohtak 124001, India.
J Insect Physiol. 2009 Apr;55(4):358-68. doi: 10.1016/j.jinsphys.2009.01.008. Epub 2009 Feb 4.
Drosophila jambulina exhibits color dimorphism controlled by a single locus but its ecological significance is not clear. Dark and light morphs differ significantly in body melanisation, desiccation resistance, rate of water loss, mating activity and fecundity. Interestingly, this species lacks clinal variation for body size, desiccation resistance and life history traits. For body melanisation, lack of geographical variation as well as plastic effects is not in agreement with a thermal melanism hypothesis. However, based on field data, there are seasonal changes in phenotypic frequencies of dark and light body color morphs which correlate significantly with variation in humidity levels. Under short-term (8h) desiccation stress, we observed higher number of assortative matings, longer copulation period and increased fecundity for dark strains as compared with light strains. By contrast, both the morphs when exposed to high humid conditions exhibited higher assortative matings and fecundity for light strains as compared with dark strains. In tropical populations of D. jambulina, body color polymorphism seems to be maintained through humidity changes as opposed to thermal melanism. Thus, seasonal changes in the frequency of body color morphs in this tropical species supports melanism-desiccation hypothesis.
黑腹果蝇表现出由单个基因座控制的颜色二态性，但其生态意义尚不清楚。深色和浅色形态在身体黑化、抗干燥能力、失水率、交配活动和繁殖力方面存在显著差异。有趣的是，该物种在体型、抗干燥能力和生活史特征方面缺乏渐变变异。对于身体黑化，缺乏地理变异以及可塑性效应与热黑化假说不一致。然而，根据实地数据，深色和浅色体色形态的表型频率存在季节性变化，这与湿度水平的变化显著相关。在短期（8小时）干燥胁迫下，我们观察到与浅色品系相比，深色品系的选择性交配数量更多、交配期更长且繁殖力增加。相比之下，当暴露于高湿度条件下时，与深色品系相比，两个形态的浅色品系都表现出更高的选择性交配和繁殖力。在黑腹果蝇的热带种群中，体色多态性似乎是通过湿度变化而不是热黑化来维持的。因此，这种热带物种体色形态频率的季节性变化支持黑化-干燥假说。
