Resource partitioning among Odonata (Insecta: Anisoptera and Zygoptera) larvae in a Hong Kong forest stream

Abstract

Larvae of 4 odonate species were common in Tai Po Kau Forest Stream: Euphaea decorata (Zygoptera: Euphaeidae), Zygonyx iris (Anisoptera: Libellulidae), Heliogomphus scorpio and Onychogomphus sinicus (Anisoptera: Gomphidae). All co-occurred within a single riffle reach and had similar life cycles. Z. iris avoided microsites near the stream banks, and had no significant best-fit regression model predicting abundance. Nevertheless, microhabitat overlaps among all 4 species were high. Dietary overlaps between Z. iris and the other species were low. H. scorpio and O. sinicus had the most similar diets of any species-pair, but among these 2 species intraspecific overlaps between large and small individuals were generally less than interspecific comparisons between equivalent-sized larvae. Ontogenetic dietary shifts and asynchronous larval development in both of these gomphids may have contributed to intraspecific partitioning of food. E. decorata had the broadest niche axes along food and microhabitat dimensions; Z. iris were relatively specialized; H. scorpio and O. sinicus made similar use of resources. Determination of morphology by phylogeny, and resultant influences on microhabitat selection and foraging behaviour, probably determined patterns of resource use resulting in closely related species showing the greatest niche overlap. -from Author