Ulbrich, K. ; Seidelmann, K.; Ruhnke, H. & H.-J. Ferenz (2000): Einfluss individuellen Nistverhaltens auf die Populationsdynamik: Ein individuen-basiertes Modell zu Wildbienen. - Mitt. dtsch. Ges. allg. angew. Ent. 12: 531-534

Abstract: Theories of parental investment and sex ratio in nest-building bees and wasps often neglect the individual variability of females in offspring provisioning and sex allocation. We examine the consequences of individual nesting behaviour of solitary bees for population development, building our argument around a study of the solitary bee Osmia rufa (L. 1758) (Apoidea: Megachilidae). An individual-based model was developed which is based on the life cycle. According to the hypothesis that a female's body size is positively correlated with components of its reproductive success such as number and size of daughters we derived a model scenario of size-related nesting behaviour. Results of model calculations demonstrate that in contrast to two random scenarios the size-related strategy causes the regulation of population parameters such as population size, sex ratio and average female body mass. Furthermore, results agree with Fisher's theory of sex allocation. After validating the size-related scenario by field observations, the model was used for assessing the extinction risk of local bee populations. Results demonstrate some aspects of the impact of agricultural management measures on the dynamics of local bee populations.

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