Population dynamics of the Gyrinid beetle Gyrinus marinus Gyll. (Coleoptera, Gyrinidae) with special reference to its dispersal activities
Data concerning reproduction, survival and dispersal of the whirligig water beetle Gyrinus marinus Gyll . were collected between 1974 and 1983 by observations and experiments in the laboratory and in a field area with about 10 populations distributed over 15 pools.The purpose of the study was to assess the importance of the dispersal activities for the population dynamics of the species.The main results can be summarised as follows: In a year two new generations emerge, one in summer and another in autumn (which subsequently hibernates).The mean survival chance is rather low as is the variation in survival chance. (Variation in survival during hibernation is, however. high.)Although there is much variation in egg production between females, the mean egg production per population varies little between different populations or years. The variation in survival during larval and pupal development is greater than that of egg production. Thus variation in egg production can have only a minor influence on the variation in numbers of emerging beetles.Exchange between populations by flying is limited to a few per cent of the specimens. It only takes place during favourable weather conditions.Intensive exchange of individuals occurs by swimming between (sub)populations that are connected by water. Exchange by swimming seems to be a result of every day swimming actvity.Key factor analyses indicate that survival during hibernation is the most important factor in determining fluctuation in population size. Larval development is a distant second. According to these analyses, all other processes, activities and developmental stages seem of minor importance for fluctuations in population size. This means that changes in the numbers of beetles is mainly dependent on factors to which the beetles cannot react directly. However, simulation experiments with stochastic models show that stability in population size is mainly achieved by the exchange of Individuals between populations Even the low rate of exchange by flight appears significantly to decrease the chance of extinction.The importance of exchange for the survival chance of such populations has implications for the exploitations (e.g. fishing) and control (e.g. pests) of natural populations, and the preservation of natural habitats.
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| Format: | Doctoral thesis biblioteca |
| Language: | English |
| Subjects: | animals, coleoptera, genetics, invasion, isolation, migration, mortality, mutations, population density, population dynamics, population ecology, population growth, selection, dieren, genetica, invasie, isolatie, migratie, mortaliteit, mutaties, populatie-ecologie, populatiedichtheid, populatiedynamica, populatiegroei, selectie, |
| Online Access: | https://research.wur.nl/en/publications/population-dynamics-of-the-gyrinid-beetle-gyrinus-marinus-gyll-co |
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