Body size and its effect on male-male competition inHylaeus alcyoneus (Hymenoptera: Colletidae)

Abstract

Body size largely determines the outcome of male-male competition in the banksia bee,Hylaeus alcyoneus. Large males invariably perch on and defend banksia flower spikes, whereas smaller males often nonaggressively patrol circuits that take them repeatedly to several flower spikes. Within the population of males perching on banksia spikes, larger individuals tend to monopolize inflorescences that are higher in banksia shrubs, whereas smaller males often occupy spikes closer to the ground. Perches defended by larger males are more quickly occupied by replacements when the original residents are experimentally removed and held in temporary captivity. When released, the original residents invariably return to and displace the smaller replacements that have taken their territories. When territory takeovers do occur, the winner is almost always larger than the previous resident, showing that residency effects are secondary to body size in determining territorial ownership.