Die Flügelreduktion bei Schmetterlingen als Anpassungsstrategie Von Wolfgang Dierl und Josef Reichholf Zoologische Staatssammlung München Abstract Wing Reduction in Lepidoptera as an Adaptive Strategy The number of Lepidoptera species with reduced wings in females, the Psychidae exclu-ded, increases towards the north and high altitudes. There are four distinct groups: Sum-mer-active species, alpine and tundral species, winter-active species, water moths and Psy-chidae. The winter and alpine species are adapted to low temperatures. In Central Europe the figure of species with reduced wings is 33, 23 of which are active during winter, 4 alpine, 1 water moth and the remaining of different types. The females of summer-active species are very large, active during light period and protected by unpalatable hairs (Orgyia spp., Lymantriidae) or substances (Heterogynis spp., Zygaenidae). The material of wings seems to be transfered into egg production. The reduction of wings in the Psychidae is a special adaptation to the casedwelling habit of the larvae. Acentropus niveus shows an increasing number of females with reduced wings towards the north. The advantage of wing reduction is twice: The body is heavier which makes egg laying below water surface easier and the dispersion on the water surface gives better chances in finding new foodplants than tlight above water surface. The largest group of species is the one adapted to low temperatures. The advantage of this adaption is a double one: During winter the density of insect eating vertebrates is very low. Many birds are migratory and the residual (Parus spp. e. g.) switch to grain feeding, small insectivorous mammals are inactive. Therefore, the selective pressure by predators is low. Secondly, almost all of these species are Geometridae with small body and large wings. The loss of energy through the surface of large wings is considerable. The wing reduction is, therefore, an important factor in saving energy during the cold season. The adaptive radiation of these species towards cold season provided selective advantages in competition with more specialized species. Most of the winter moths are polyphagous. The disadvantage of wing reduction is balanced by special dispersal mecha-nisms in the newly hatched larvae and by their polyphagous habit. The high fecundity on the contrary is compensated by high mortality caused by adverse weather rather than by predation (less than 5 %). In evolution, the adaptation to the cold season served as a biotic strategy to escape the periods of high competition and predation levels, the abiotic implications of which were resolved with the saving of energy by wing reduction. The saving of energy by wing reduction alone is not able to compensate the disadvantages which can be seen in the small populations of wing reduced summer moths. The adjustment to the cold season with less enemy pressure seems to be the main selective factor for the evolution of this adaptation. 27
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