Impact of different population size on male behaviour in Libellula fulva (Odonata: Libellulidae)

摘要

Dragonflies are popular subjects in population ecology stud-ies. These insects often compose small populations of a few thousand individuals, where the recapture ratio could be very high. They are easy to catch, to mark, and to watch. The pop-ulations are often closed making immigration and emigration negligible (CORBET 1999). The population size is estimated on the base of recapture ratio of marked individuals. In the case of territorial species the estimation is based only on the marked males because the recapture rate of the females is low (PAJUNEN 1962). The behaviour of dragonfly males can change when the population size alters. In males of Calopteryx h. haemorrhoi-dalis at high population size, most of the copulations are forced (CORDER° & ANDRES 2002), and the post copulation guarding becomes more frequent (CORDERO 1998). We ana-lysed mating behaviour and niorphometrical parameters of males in 2 closed Libellula fulva (Muller, 1764) populations with different dragonfly densities. Our hypothesis was that dragonfly males use different strategies to obtain mates in different population densities.