| Habitat selection is a complex process with both biotic and abiotic factors acting to influence the habitat a species occupies. Larvae of the odonate family Libellulidae are predominantly benthic, although some species are frequently associated with vegetation rooted in the sediments. The purpose of this study was to investigate how sediment type influences habitat selection in larvae of four libellulid species: Pachydiplax longipennis, Libellula quadrimaculata, Tramea lacerata, and Libellula luctuosa. Another aim was to investigate the influences of vegetation, prey availability, and predators on habitat selection.;Both laboratory and field data were utilized in this study. The laboratory research consisted of eight experiments. Experiments 1--4 were designed to determine if sediment type was a factor in habitat selection in the presence and absence of different vegetation types. Experiment 5 and 6 examined the influence of prey availability and hunger with respect to sediment and vegetation. To determine if characteristics of a habitat alter the larva's response to a predator, Experiment 7 was designed to expose larvae to different combinations of sediment and vegetation with and without a predator present. Experiment 8 examined influences of sediment type in early instar larvae habitat selection. Field data was obtained via dragonfly larval sampling from May to October 2011.;In laboratory experiments, libellulid larvae discriminated among sediment despite influences from other factors such as vegetative structure, prey availability, and predator presence. Whether the simulated vegetation was with screening or plants, larvae were found significantly more often with vegetation than bare soil with the exception of Libellula quadrimaculata. With the addition of a predator, all species of larvae were observed closer to the predator cage when on the previously established "preferred" soil type than when on the other sediments. With the addition of prey, there was no difference in habitat selection between starved and fed individuals except in the case of Pachydiplax longipennis. The most distinct similarity in the results for all four species was a significant avoidance of sand. Field data showed that the four species in this study demonstrated non-random association with substrate. The larvae species studied were found most often in natural sites that reflected the established "preferred" substrate from lab experiments, except in the case of Tramea lacerata larvae. For T. lacerata, substrate composition may be less important in habitat selection than other factors. |
