Elephant impact on dragonflies |
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Authors: | Michael J Samways Paul B C Grant |
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Institution: | (1) Department of Conservation Ecology and Entomology, Centre for Agricultural Biodiversity, University of Stellenbosch, Post Bag X1, Matieland, 7602, South Africa |
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Abstract: | African elephants and other indigenous megaherbivores have a major impact on local vegetation structure, including aquatic
communities, as their big feet and large mass pound the fringes of water bodies. This disturbance is likely to have a profound
influence on the structure and composition of insect assemblages in these habitats. We investigated which dragonfly (Odonata)
species were tolerant of trampling by elephants and other game. Assemblage composition differed according to extremely high,
very high or high disturbance levels. Dragonfly abundance was greatest where impact was high, and decreasing when disturbance
became very high or extremely high. Several odonate species are well-adapted to fairly high levels of disturbance, although
too much is impoverishing. Medium and low impact sites were geographically separated, and this, combined with much lower disturbance
levels, had a considerable influence on promoting regional dragonfly diversity. Several regional specialist species only occurred
in the geographically separated, low-impact sites. The full complement of dragonflies is present only when there is a combination
of various disturbance levels combined with spatial variation. Elephant impact is similar to that of humans, with too much
of either or both, leading to a species-poor, habitat-generalist dragonfly assemblage. |
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Keywords: | Elephant trampling Dragonfly biodiversity Parallels with human impact |
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