Reproductive ecology of Drosophila obscura: A cold adapted species

The study of insect reproductive ecology is essential to determine species
distributions and fate under changing environments. Species adapted to
harsh environments are good examples to investigate the reproductive
mechanisms that allow them to cope with the challenging
conditions.  We here focus on studying for the first time the
reproductive ecology of a cold-adapted D. obscura strain collected in
Finland (subarctic climate region). We tested several reproductive traits
such as fertility and fecundity to observe the onset of reproduction and
gauge when sexual maturity is reached in both males and females. We
combined these measures with an analysis of changes of their reproductive
organs shortly after eclosion. We found that males matured several days
before females and that this process was underpinned by female egg
maturation and male accessory gland growth, while sperm was already
present in two-day old males. This delayed maturation is not observed to
the same extent in other closely related species and might be a signature
of exposure to harsh environments. Whether this delay is an adaptation to
cope with variation in resource availability or prolonged unfavorable
temperatures is though not clear. Finally, our study adds to the set of
reproductive mechanisms used by cold adapted species and the information
presented here contributes to understanding the breadth of Drosophila
reproductive ecology.

昆虫生殖生态学研究，对于明确环境变化下物种的分布格局与存续命运至关重要。适应严苛环境的物种，是探究其得以在恶劣条件下存活的生殖机制的绝佳研究对象。本研究首次聚焦于采集自芬兰（亚寒带气候区）的耐寒暗果蝇（D. obscura）品系的生殖生态学特征。我们通过检测生育力、繁殖力等多项生殖性状，观测其生殖起始状态，并评估雌雄个体的性成熟节点；同时结合羽化后短期内生殖器官的形态变化分析，对上述结果进行整合。研究发现，雄性的性成熟时间较雌性提前数日，这一过程的核心支撑机制为雌性卵成熟与雄性附腺发育，而羽化两日龄的雄性体内已存在精子。在其他近缘物种中，并未观察到同等程度的性成熟延迟现象，这一特征或为其适应严苛环境的标志性性状。不过，这种性成熟延迟究竟是为适应资源可获得性的波动，还是为应对长期低温等不利环境，目前仍未明确。最后，本研究丰富了耐寒物种生殖机制的相关研究积累，本次呈现的研究数据也有助于深化对果蝇属（Drosophila）生殖生态学全貌的认知。