PARENT SESSION
Poster Session #50: Evolutionary Ecology.
Friday, August 10, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall
129
Altered color morph frequency in a lake littoral population of Asellus aquaticusL. (Isopoda) .
Hargeby, Anders1, Johansson, Jonas, 1
ABSTRACT- Environmental change generally alters selection and thereby the genotype distribution in populations. Pigmentation of the isopod Asellus aquaticus L. changed towards a higher frequency of brightly colored individuals in Lake Krankesjon, Sweden, during a 15-year period of expanding submerged vegetation. The altered frequency of color morphs occurred only in a habitat with submerged plants, consisting mainly of stoneworts (Chara spp.). Individuals in a reed habitat nearby remained dark. To test whether these changes were due to genetic or plastic responses we performed breeding experiments in the lake. Pairs in various combinations of bright, dark and intermediate individuals were incubated for two months and the color of the offspring was measured. The results showed that color was to a large extent genetic. Combinations of dark males with bright females and vice versa resulted in similar, high, frequency of intermediate offspring. Intermediate parents also produced intermediate offspring. These results indicate that the color alteration observed in Asellus was the result of changed allele frequency in the population over the 15-year period. We intend to use this continuous, heritable character of Asellus for further studies on how natural and sexual selection may act on natural populations in a changing environment.
KEY WORDS: environmental change, population, genetic alteration, Asellus aquaticus