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 Urothemis edwardsii 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.