Trophic ecology of adult male Odonata. II. Dietary contributions of aquatic food sources

Abstract

Abstract. 1. Insects that emerge from rivers provide nutritional subsidies to local riparian predators. Adult damselflies and dragonflies often benefit from aquatic resources, but their high mobility and evasiveness have made it difficult to monitor their diets.2. A dual fatty acid and stable isotope analysis approach was used to investigate the links between Odonata size and behaviour with proportions of their aquatically derived nutritional sources. Additionally, the study investigated the variation in dietary contributions of aquatic food sources to Odonata between two sections of a river, each with different aquatic productivity rates.3. Variations in body size and foraging method of Odonata in the Kowie River (South Africa) contributed to differences in the contributions of aquatic food sources to their diets. Large Odonata that consumed prey in flight had smaller proportions of aquatic indicator fatty acids and stable isotope-generated proportions of aquatic food sources than did the smaller Odonata that consumed prey from perches.4. There was a considerable amount of interspecific variation in indicators of aquatic feeding, but Odonata at an upstream site had smaller proportions of aquatic indicators than those at a downstream site which had higher insect emergence rates.5. The findings of this study contribute information on the dynamics of feeding ecology among adult Odonata, and the substantial contributions of aquatic prey (>80% of total diet in some cases) indicated that cross-boundary trophic linkages via odonates are strong in the Kowie River.

Holo- and hemimetabolism of aquatic insects: Implications for a differential cross-ecosystem flux of metals

“…predators), it is possible that class B metals may also exhibit biomagnification within terrestrial food chains. Although the assessment of direct trophic linkages was beyond the scope of this study, Odonata adults and riparian spiders have been shown to feed primarily on aquatic insectsa diet which can account for up to 80 and 90% of their mass, respectively (Paetzold et al, 2005;Jackson et al 2016;Chari et al, 2017). It is therefore possible that the majority of their metal exposure was due to feeding on metal-contaminated prey emerging from the contaminated freshwaters (i.e.…”

Faecal analyses and alimentary tracers reveal the foraging ecology of two sympatric bats

“…Potential food sources of insect prey were also sampled to obtain reference isotope and fatty acid levels from the original source. These food sources included benthic algae and leaves from terrestrial plants [44]. Benthic algae (i.e.…”

“…The areas of the ellipses represented the calculated fatty acid niche widths. Using fatty acids in niche analysis in this way has been successfully used in other studies [44,51]. Values of 95% credibility intervals and Bayesian posterior probabilities (P < 0.05) were used to test for significant differences between species for each location.…”

“…Running mixing models for predators by only including primary producers, rather than insect and other middle trophic level prey allows one to determine what the baseline sources of food are for a consumer's diet. This allows one to eliminate much variability from the models that would arise as a result of using the actual prey [44,70,71]. To run the mixing models, we used a discrimination factor of 'zero' in all our models [72,73].…”

Edible dragonflies and damselflies (order Odonata) as human food – A comprehensive review

“…Their ability to fly over long distances may be a challenging factor when rearing. Some insects such as adult dragonflies and damselflies are very mobile therefore little is known about which organisms they feed on and how their diets can be monitored (Chari et al, 2018). This is another challenge which has been highlighted in insect farming.…”