Adaptive significance of amylase polymorphism in Drosophila . XII. density- and frequency-dependent selection at the Amy locus in Drosophila subobscura reared on media with different carbohydrate composition

Abstract

Egg‐to‐adult viability is studied in the progeny of the flies of different genotypes according to S and F alleles of Amy locus of Drsophila subobscura . This component of fitness is observed in the single and mixed cultures with various frequencies of three genotypes (S/S, F/F and S/F) under conditions of low (LD) and high densities (HD) on three types of media with different carbohydrate composition. In such multifactorial experimental conditions, density‐ and frequency‐dependent selection on certain Amy genotypes was observed. Genotype frequencies and carbohydrate composition have significant effect on the viability of Amy genotypes. The significant intergenotypic differences exist, mostly at HD conditions. The heterozygous genotype S/F has generally lower viability which decreases with its increased frequencies, on all media at LD or HD. The results suggest a high level of complexity and interaction between these two types of balanced selection.

Adaptive significance of amylase polymorphism in drosophila, XV: Examination of genotype-by-environment interactions on the viability, developmental time and stability of drosophila subobscura homozygous for Amy during exposure to nutritional changes

“…This gene polymorphism has its clearly defined biochemical phenotype, and the level of amylase activity is regulated by the components and conditions of the nutrient composition. The biochemical and physiological differences caused by the genetic structure of the Amy locus appear evident from previous results through the variability of fitness components among D. subobscura flies reared on different carbohydrate sources (Andjelković et al, 2003). The viability of homozygotes with the "slow" Amy allele (Amy S /Amy S ) genotype was significantly better than that of the homozygotes with the "fast" Amy allele (Amy F /Amy F ) genotype on substrates with a higher concentration of starch as a stressful factor.…”

“…Adaptive significance and genetic variability which correlate with environmental change are manifested through the well-known polymorphism of the amylase locus (Amy) in several Drosophila species (Milanović et al, 1989;Matsuo et al, 1999;Stamenković-Radak et al, 2003). Because α-amylase interacts directly with the nutritive substrate (it hydrolyses the internal α-1,4 glycoside bond of starch to maltose, glucose and α-dextrin to produce energy), Amy is a potential target gene of adaptive evolution.…”

Starch supplementation modulates amylase enzymatic properties and amylase B mRNA level in the digestive gland of the Pacific oyster Crassostrea gigas

“…Its role might be crucial in the adaptation of C. gigas to variation in starch concentration in the diet, whereas amylase gene A has already been suggested to adapt digestive processes in response to variation in quantity of the same alga in the oyster diet (Huvet et al, 2003). Adaptive significance of gene-enzyme polymorphism depending on the carbohydrate composition of the diet, especially at limiting or low level, would make an interesting study, through a multifactorial experiment like that developed for Drosophila subobscura (Andjelković et al, 2003), particularly considering that activity regulation is mostly important for the adaptation to the environment with respect to the level of starch it contains (Fujimoto et al, 1999). Tables Table 1 Wet flesh weight (in grams) of oysters after 10 (T1) and 18 (T2) days of food conditioning in four different treatments.…”