Perch selection by male dragonflies (Odonata, Anisoptera) related to competitive ability and species composition

Abstract

PERCH SELECTION IN MALE DRAGONFLIES (ODONATA, ANISOPTERA) RELATED TO COMPETITIVE ABILITY AND SPECIES COMPOSITION Jessica L. Beard Old Dominion University, 2015 Director: Dr. Deborah Waller Males of many species of dragonflies (Odonata, Anisoptera) establish territories in aquatic habitats where they compete with other males for access to food and females. Territorial males typically perch on emergent vegetation and chase rival males who intrude into their territories. This dissertation research examined the role of male size in perch height selection, position on the perch, and competitive ability. Four hypotheses were tested: 1) Dragonfly species would vary by size and that territorial species would show sexual size dimorphism (SSD), 2) Perch height selection would be related to dragonfly size, 3) Position on the perch would be related to male size, with larger males selecting perch tops and smaller inferior competitors choosing the sides of perches, and 4) Intraspecific competition would be more important than interspecific competition. Research was conducted at four lakes in southeastern Virginia from 2011-2014. For size measurements, male and female dragonflies were captured and measured for total body length, abdomen length, cerci length, forewing length and width, hindwing length and width and fresh mass. For perching experiments, alternating short (30cm above waterline) and tall (90cm above waterline) bamboo perches were placed in two rows, 0.5m and 2.0m from the shore. Any dragonflies that alighted on perches were recorded for species, gender, perch position and length of occupancy. Any interactions with conspecific or heterospecific dragonflies were recorded. Results showed that dragonfly males varied significantly among species in all parameters measured, and SSD was found for some parameters for some of the species. In particular, females of several species had greater forewing and hindwing widths than males, perhaps related to selection for energy conservation in females. There was no association between dragonfly size and perch height selection. Four species frequently perched on the sides rather than the tops of