Department of Zoology, Banaras Hindu University, Varanasi, India.
Department of Biochemistry, University of Delhi South Campus, New Delhi, India.
Heredity (Edinb). 2021 Sep;127(3):278-287. doi: 10.1038/s41437-021-00449-2. Epub 2021 Jun 23.
Environmental seasonality is a potent evolutionary force, capable of maintaining polymorphism, promoting phenotypic plasticity and causing bet-hedging. In Drosophila, environmental seasonality has been reported to affect life-history traits, tolerance to abiotic stressors and immunity. Oscillations in frequencies of alleles underlying fitness-related traits were also documented alongside SNPs across the genome. Here, we test for seasonal changes in two recombination characteristics, crossover rate and crossover interference, in a natural D. melanogaster population from India using morphological markers of the three major chromosomes. We show that winter flies, collected after the dry season, have significantly higher desiccation tolerance than their autumn counterparts. This difference proved to hold also for hybrids with three independent marker stocks, suggesting its genetic rather than plastic nature. Significant between-season changes are documented for crossover rate (in 9 of 13 studied intervals) and crossover interference (in four of eight studied pairs of intervals); both single and double crossovers were usually more frequent in the winter cohort. The winter flies also display weaker plasticity of both recombination characteristics to desiccation. We ascribe the observed differences to indirect selection on recombination caused by directional selection on desiccation tolerance. Our findings suggest that changes in recombination characteristics can arise even after a short period of seasonal adaptation (~8-10 generations).
环境季节性是一种强大的进化力量，能够维持多态性，促进表型可塑性，并导致风险分散。在果蝇中，环境季节性已被报道会影响生活史特征、对非生物胁迫的耐受性和免疫力。与基因组中的 SNPs 一起，还记录了与适应性相关特征的等位基因频率的波动。在这里，我们使用三个主要染色体的形态标记，在来自印度的自然 D. melanogaster 种群中测试了两种重组特征（交叉率和交叉干扰）的季节性变化。我们表明，冬季收集的干燥季节后，与秋季相比，果蝇具有更高的耐旱性。这种差异也适用于与三个独立标记品系的杂交种，表明其具有遗传而非塑性性质。在 13 个研究间隔中的 9 个和 8 个研究对的间隔中的 4 个中记录到了交叉率（在 9 个研究间隔中的 9 个）和交叉干扰（在 8 个研究对的间隔中的 4 个）的显著季节性变化；冬季群体中通常更频繁地出现单交叉和双交叉。冬季果蝇的两种重组特征对干旱的可塑性也较弱。我们将观察到的差异归因于对耐旱性的定向选择对重组的间接选择。我们的研究结果表明，即使在短期季节性适应（~8-10 代）之后，重组特征的变化也可能发生。
