Voltinism and larval population structure of Calopteryx splendens (Odonata: Calopterygidae) in the Po Valley


Adaptation of life-history traits is an important factor for the success of insects. Voltinism is a feature that descends from several life-history traits and, given that the latter depend on the specific environment of growth, voltinism can vary between populations across latitudes or habitats. In addition, some insects, like many odonates, have developed different patterns of voltinism within the same population, due to mechanisms of cohort splitting. Calopteryx splendens (Odonata: Calopterygidae) is a widespread damselfly in Europe that has been extensively studied regarding its evolutionary ecology, but detailed studies about its voltinism are relatively scarce and confined to the central and northern areas of Europe. So we investigated the voltinism and larval development of a population of C. splendens both by captive rearing and in the field in Northern Italy, the southernmost area in which its voltinism has been studied so far. We found an earlier start of larval growth, with respect to previous studies. Additionally, the head-width of larvae of the same instar decreased with the cohort ageing. Finally, the results are consistent with a two-groups emerging pattern that may support partial semivoltinism or partial bivoltinism of C. splendens in Northern Italy.

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