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

Abstract

SUMMARY(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.

A steep cline in ladybird melanism has decayed over 25 years: a genetic response to climate change?

“…A steep cline when first surveyed in 1978-1981(Brakefield, 1984a showed some progressive decay up until 1995 (de Jong and Brakefield, 1998). This was correlated with an increase in hours of spring sunshine and in spring temperatures.…”

An Ancient Mitochondrial Polymorphism in Adalia bipunctata Linked to a Sex-Ratio-Distorting Bacterium

“…Long-distance dispersal of both sexes occurs to and from over-wintering sites or following crashes in prey numbers (Majerus 1994). More local movements occur between host plants, and here females migrate somewhat more than males, perhaps due to their longer lifespan (Brakefield 1984;Tinsley 2003). In a more formal approach to this problem, the HKA test was still significant after correction for population subdivision, despite several conservative assumptions.…”

Sperm competition and melanic polymorphism in the 2-spot ladybird, Adalia bipunctata (Coleoptera, Coccinellidae)

“…An hypothesis about the way in which selection influences the colour polymorphism involves thermal melanism, in which the melanic morph has an advantage relative to the lypica morph under circumstances of limited sunshine levels (Lusis, 1961;Muggleton et at., 1975;Brakefield, 1984b;Brakefield & Willmer, 1985;Brakefield & Lees, 1987). An essential feature of this hypothesis is the presence of food (aphids) for the ladybirds.…”