Thermal ecology of Interior Alaska dragonflies (Odonata: Anisoptera)

Abstract

Summary We examined the thermal ecology of Interior Alaska dragonflies (Odonata: Anisoptera). The relationships between mass and passive cooling rate, wing loading, minimum flight temperature (MFT) and thermoregulating ability were examined. These properties were also compared between the behavioural classes: perchers and fliers. All factors with the addition of seasonal and daily flight activity were related to generalized thermal strategies. Passive cooling rate decreased while wing loading and MFT increased with mass. While all species were able to elevate thoracic temperature, larger species were better able to maintain a constant temperature. Both the smallest and largest species of dragonflies were capable of activity at ambient temperatures of approximately 14 °C by employing different thermal strategies: low MFT and physiological heat production, respectively. For small species active in cool conditions low MFT may be favoured even if accompanied by poor thermoregulating ability. By contrast, thermoregulation and specialization for high‐temperature performance may be favoured in both small and large species during the warmer summer flight season. The smallest and largest dragonflies in Interior Alaska have the shortest and longest daily activity periods, respectively. However this pattern does not hold for the intermediate‐sized dragonflies. Thermal strategy displays no clear relationship to daily activity pattern.