Population Growth Index Research Articles

Effects of seed masting of bilberry, oak and spruce on sympatric populations of bank vole (Clethrionomys glareolus) and wood mouse (Apodemus sylvaticus) in southern Norway

AbstractIn southern Norway, population fluctuations of the herbivorous bank vole Clethrionomys glareolus and the granivorous wood mouse Apodemus sylvaticus were analysed in relation to mast seeding of bilberry Vaccinium myrtillus, sessile oak Quercus petraea and Norway spruce Picea abies. Bilberries ripen in August, acorns are dispersed in September, whereas spruce seeds are usually dispersed during winter or spring. The bilberry index of both the current and previous year contributed significantly to explain the population growth indices of bank vole. The spruce seed index significantly influenced only the bank vole, whereas the acorn index significantly influenced only the wood mouse, apparently through increased winter survival. Because of the lack of significant responses to bilberry masting by granivorous wood mice, we conclude that the most likely explanation for the observed peak populations of bank voles in post‐mast years of bilberry is that high seed crops have a positive influence on the chemical composition of bilberry plants, which are important as food for bank voles during winter.

Population cycles of autumnal moth, Epirrita autumnata, in relation to birch mast seeding.

We investigated the relationship between flowering peaks of the mountain birch, Betula pubescens ssp. czerepanovii, and population levels of the autumnal moth Epirrita autumnata in Ammarnäs, Swedish Lapland, during 1968-2000, and in Budal, Central Norway, during 1972-2000. There was a significant correlation between the two moth series, both of which showed three well-defined population cycles during the study period. In both areas, the population growth index of the moth was negatively related to population size, but also to the number of years since the previous flowering peak of mountain birch. In the northern study area, Ammarnäs, there was an additional positive effect of the winter temperature index, probably due to increased mortality of moth eggs during cold winters. No significant relationships were found between the number of birch female catkins and larval density in the previous 2years. Both in Ammarnäs and in an area without moth outbreaks in south-eastern Norway, birch flowering was positively related to temperatures during flower bud formation and to the number of years since the previous flowering peak. The results support the idea of a lower content of chemical defence compounds in birch leaves after a mast reproduction, though we cannot exclude the possibility that the negative relationship between flowering and moth population levels was influenced or caused by stress associated with defoliation during moth outbreaks.

Applied Stochastic Processes: A Biostatistical and Population Oriented Approach.

Introduction to Stochastic Processes: Basic Concepts. Random Walk and Markov Process. Non-Markov Process and Renewal Theory. Martingales. Counter Theory and Age-Replacement Policy. Palm Probability and Its Applications. Stochastic Epidemic Processes. Stochastic Processes of Clinical Drug Trials. Techniques of Stochastic Processes in Mortality Analysis--Applications on Life Table. Techniques of Stochastic Processes in Fertility Analysis. Techniques of Stochastic Process for Demographic Analysis--Population Growth Indices. Stochastic Processes on Survival and Competing Risk Theory. Stochastic Processes in Genetics. Appendix. Index.

The potential geographical distribution of the Old World screw‐worm fly, Chrysomya bezziana

The potential geographical distribution and relative abundance of the Old World screw-worm fly, Chrysomya bezziana Villeneuve (Diptera: Calliphoridae) as determined by climate, was assessed using CLIMEX, a computer program for matching climates. CLIMEX describes the relative growth and persistence of animal populations in relation to climate. The observed global distribution of C.bezziana was compared with the potential distribution predicted by CLIMEX. The differences in the two distributions indicate the areas at risk of colonization, with particular reference to Australia and the Americas. According to the model, the potential area of permanent colonization in Australia extends south to the mid-coast of New South Wales. Comparison of areas suitable for permanent establishment with the potential summer distribution indicates that large additional areas, carrying most of the continent's livestock, could be colonized in the summer months. Seasonal population growth indices are presented for three ports in Australia at which screw-worm fly specimens have been collected by quarantine authorities. They indicate the relative risk associated with introductions at different places in different seasons and so provide valuable planning information for quarantine authorities. The CLIMEX predictions for C.bezziana in North America are shown to be similar to the recorded distribution limits of the New World screw-worm fly, Cochliomyia hominivorax (Coquerel). The fly could also colonize South America, as far south as southern Brazil and midway through Argentina.