A long-term study on interactions between the Adh and αGpdh allozyme polymorphisms and the chromosomal inversion In(2L)t in a seminatural population of D. melanogaster

Abstract

The Adh and αGpdh allozyme loci (both located on the second chromosome) showed considerable fluctuations in allele frequencies in a seminatural population of Drosophila melanogaster during 1972–97. Both long‐term and short‐term fluctuations were observed. The short‐term fluctuations occurred within almost all years and comparison of allele frequencies between winters and summers showed significantly higher AdhS (P < 0.001) and αGpdhF (P < 0.01) allele frequencies in summers. Frequencies of these alleles were significantly positively correlated with environmental temperature, suggesting the adaptive significance of these allozyme polymorphisms. Frequency changes of the Odh locus (located on the third chromosome) showed no seasonal pattern and were not correlated with environmental temperature. Almost all short‐term and long‐term increases in AdhS frequency were accompanied by a corresponding decrease in αGpdhS frequency (r = –0.82, P < 0.001) and vice versa. Further analysis showed that gametic disequilibria between the Adh and αGpdh loci, which frequently occurred, were due to the presence of inversion In(2L)t located on the same chromosome arm and In(2L)t frequencies were positively correlated with environmental temperature. Gametic disequilibria between Adh and Odh and between Odh and αGpdh were hardly observed. Because In(2L)t is exclusively associated with the AdhS/αGpdhF allele combination, the observed correlated response in Adh/αGpdh allele frequencies is (at least partly) explained by hitchhiking effects with In(2L)t. This means that the adaptive value of the allozyme polymorphisms has been overestimated by ignoring In(2L)t polymorphism. Fluctuations in Adh allele frequencies are fully explained by selection on In(2L)t polymorphism, whereas we have shown that αGpdh frequency fluctuations are only partly explained by chromosomal hitchhiking, indicating the presence of selective differences among αGpdh genotypes in relation with temperature and independent of In(2L)t. Frequency fluctuations of αGpdh and In(2L)t are consistent with their latitudinal distributions, assuming that temperature is the main environmental factor varying with latitude that causes directly or indirectly these frequency distributions. However, the results of the tropical greenhouse population show no correlation of Adh (independent of In(2L)t) and Odh allele frequencies with environmental temperature, which may indicate that the latitudinal distribution in allele frequencies for these loci is not the result of selection on the F/S polymorphism in a direct way.

The conversion of variance and the evolutionary potential of restricted recombination

“…More recent work on D. suboobscura has indicated that the frequencies of certain inversions within both natural and laboratory populations are strongly correlated with different temperature regimes and seasons (Orengo and Prevosti, 1996;Kamping and Van Delden, 1999). Clines in inversion frequency related to variation in life history, morphological, and fitness-related traits and correlated to different climatic conditions have been characterized in D. suboobscura (Prevosti et al, 1988;Orengo and Prevosti, 1996;Schaeffer et al, 2003), other fruit fly species (Inoue et al, 1984;Rodriguez et al, 2000), and in mosquitoes (Coluzzi et al, 1979).…”

A Rapid Shift in a Classic Clinal Pattern in Drosophila Reflecting Climate Change

“…The combined data set from these different periods showed a significant difference in elevation but not in the slope of the regression lines ( Fig. 1 and Table 1), with elevation shifting in the direction expected with rising temperatures and global warming (6,16). Because the Adh S allele that predominates in tropical populations is now at a higher frequency in all populations, there has been a tendency for populations to evolve toward the genetic composition of lower latitude populations.…”

An independent non-linear latitudinal cline for the sn-glycerol-3-phosphate (α-Gpdh) polymorphism of Drosophila melanogaster from eastern Australia

“…We found strong LD between In(2L)t and the Adh S allele in southern populations, but not in the north. The higher level of linkage at temperate latitudes is consistent with the findings of van 't Land et al (2000) who found a strong association between Adh S and a-Gpdh F at temperate latitudes in Central and South America that was most likely caused by In(2L)t. Strong gametic disequilibrium has also been observed for Adh and a-Gpdh in the laboratory and a semi-natural population (van Delden & Kamping, 1989 ;Kamping & van Delden, 1999) although the degree of linkage varied considerably over seasons and under different environmental conditions. We did not detect significant LD between Adh and a-Gpdh in any field populations, despite the relatively high Dk values in several instances.…”

“…1). The a-Gpdh locus is situated within the cosmopolitan inversion, In(2L)t, which is usually in positive linkage disequilibrium with the a-Gpdh F and Adh S alleles (Kamping & van Delden, 1999 ;van 't Land et al, 2000). Like other common inversions in D. melanogaster, In(2L)t is clinally distributed with latitude (Knibb et al, 1981;Knibb, 1982 ;Anderson et al, 1987) and therefore may confound latitudinal patterns of a-Gpdh.…”