Winter survival by dragonfly adults in the Cape Floristic Region 00

Abstract

Little is known about the ability of adult dragonfly individuals to survive into or over the winter in the Cape Floristic Region (CFR), a significant biodiversity hotspot in South Africa. Dragonfly species richness and abundance were recorded throughout winter and into spring in Jonkershoek Nature Reserve. Several environmental variables were also measured. Individuals of eight dragonfly species (four in the Anisoptera and four in the Zygoptera) survived into the winter as adults, even though winter conditions would seem unfavourable (wet, windy and cold) for them in this area at this time of year. Five of these species were CFR endemic or national endemic species or subspecies, illustrating local adaptation. Of the remaining three, all of which are widely distributed species in Africa, only one, Trithemis arteriosa, clearly appeared as old, overwintering adults into spring, indicating its versatility both in its adaptation to winter conditions as well as its well-known tolerance of biotope variability. This may partly explain its success as one of South Africa’s most common and widespread species. Although many environmental variables were measured and correlated with species richness and abundance, it was only air temperature and associated low relative humidity that were highly positively significant. This emphasizes that the species were opportunistic during the winter and only took to the air on clear, sunny and warm winter days during the cold season. Unlike some other local studies conducted in the summer, these winter results indicated that water flow was a less important variable than that of the seemingly critical variable of temperature during this season. In addition, the importance of emergent vegetation also played a role and appears important for shelter on cool, wet, windy days which precluded flight activity.

Keywords: Odonata, winter survival, South Africa, endemic species, Trithemis arteriosa

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