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Ecological Studies on the Polymorphic Ladybird Adalia bipunctata in the Netherlands. I. Population Biology and Geographical Variation of Melanism

Paul M. Brakefield
Journal of Animal Ecology
Vol. 53, No. 3 (Oct., 1984), pp. 761-774
DOI: 10.2307/4658
Stable URL: http://www.jstor.org/stable/4658
Page Count: 14
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Ecological Studies on the Polymorphic Ladybird Adalia bipunctata in the Netherlands. I. Population Biology and Geographical Variation of Melanism
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Abstract

(1) Samples of the polymorphic two-spot ladybird Adalia bipunctata were collected at seventy-five sites in the Netherlands and northern Belgium. Most sites were on four transects up to 120 km long. Sequential sampling at thirteen sites was used to examine basic population biology. (2) Shrubs, especially Rosa rugosa and Crataegus spp., provide feeding and mating habitats in late April and May following hibernation. Some oviposition may also occur. Adults disperse from mid-May to trees, particularly Tilia spp., which are the principal habitats for egg laying in many populations. At some sites in some years a substantial second, late summer or autumn generation occurs. Reproduction probably tends to occur earlier inland than on the coast. There are differences in timing between years. (3) Frequencies of melanics are 1-15% in the north-west and >50% inland in the south-east. Steep clines occur over part of the transition between these regions, possibly due to a partial barrier to gene flow. Frequency changes were probably more marked for the quadrimaculata than the sexpustulata melanic morph. (4) Among the correlations between melanic frequency and climatic variables are negative ones with an index of oceanity, relative humidity and length of sunshine. The last is consistent with thermal melanism. The interpretation of the relationships with environmental variables is discussed.

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