Legacy of Extinction? Reduced Body Size and Ornamentation in a Re-established Population of a Critically Endangered Dragonfly

The extirpation and reintroduction of species offer valuable opportunities to understand how life history traits respond to habitat restoration and demographic bottlenecks. In insects, such trait shifts remain poorly explored despite growing concern about global declines. In this study, we conducted a comparative assessment of morphological traits of the locally Critically Endangered dragonfly <i>Urothemis edwardsii</i> in the source (Lake Bleu) and recently re-established (Lake Noir) populations in northeastern Algeria. We measured body length, wing length, and wing spot area (ornament) of adult males during the peak flight season. Our data showed that individuals from the re-established population in Lake Noir had significantly smaller body and wing lengths than those from Lake Bleu. Wing spot area was also smaller in Lake Noir. The seasonal increase in body size was sharper in Lake Bleu, indicating limited capacity to gain mass during larval development in Lake Noir. This study highlights how extinction and reintroduction may influence trait expression in aquatic insects and underscores that even 25 years after major perturbation, habitat still does not confer optimal conditions for larval growth.

物种的本地灭绝与再引入，为探究生活史性状如何响应生境恢复与种群瓶颈提供了宝贵契机。尽管全球昆虫种群衰退引发的担忧与日俱增，但此类性状转变在昆虫类群中仍鲜有研究。本研究针对阿尔及利亚东北部的本土极危蜻蜓<em>Urothemis edwardsii</em>，对其源种群（布卢湖，Lake Bleu）与新近重建的努瓦尔湖（Lake Noir）种群的形态性状开展了比较评估。我们于成虫飞行高峰期，对成年雄性个体的体长、翅长以及翅斑面积（装饰性结构）进行了测量。数据显示，相较于布卢湖种群，努瓦尔湖重建种群的个体体长与翅长均显著更短；努瓦尔湖种群的翅斑面积同样更小。布卢湖种群的体型季节性增长更为显著，这表明努瓦尔湖种群在幼虫发育阶段的体重增长能力受限。本研究揭示了物种灭绝与再引入如何影响水生昆虫的性状表达，并强调：即便在重大扰动发生25年后，当地生境仍未为幼虫生长提供最优条件。