Evolutionary dynamics of molecular markers during local adaptation: a case study in Drosophila subobscura

Abstract

Here we present a correction to our article "Evolutionary dynamics of molecular markers during local adaptation: a case study in Drosophila subobscura". We have recently detected an error concerning the application of the Ln RH formula – a test to detect positive selection – to our microsatellite data. Here we provide the corrected data and discuss its implications for our overall findings. The corrections presented here have produced some changes relative to our previous results, namely in a locus (dsub14) that presents indications of being affected by positive selection. In general, our populations present less consistent indications of positive selection for this particular locus in both periods studied – between generations 3 and 14 and between generation 14 and 40 of laboratory adaptation. Despite this, the main findings of our study regarding the possibility of positive selection acting on that particular microsatellite still hold. As previously concluded in our article, further studies should be performed on this specific microsatellite locus (and neighboring areas) to elucidate in greater detail the evolutionary forces acting on this specific region of the O chromosome of Drosophila subobscura.

Correction

We have recently detected an error in our article [1], concerning the application of the Ln RH formula to our microsatellite data. This necessitates some changes in the results and figures presented in the "Testing for positive selection during laboratory adaptation" results section. Here we provide the corrected data and discuss its implications for our overall findings.

Corrected Ln RH values comparing generations 3 and 14 remain significantly different between loci in both TW and AR populations (one-way ANOVA; p < 0.001). Standardized Ln RH values for microsatellite locus dsub14 fall outside the 95% confidence interval of the standard normal distribution for AR₁ (p < 0.03). AR₂ and AR₃ populations show a marginally significant deviation from expectation of neutrality (p < 0.06 for AR₂; p < 0.07 for AR₃). But AR populations present less consistent indications of positive selection between generations 3 and 14 than previously indicated [1]. In addition, standardized Ln RH values for dsub14 between generations 3 and 14 in TW populations no longer differ significantly from neutral expectation, despite the fact that the Ln RH values for these populations remain high (Fig. 1).

Figure 1.

Standardized Heterozygosity ratios (Ln RH) between generations 3 and 14. Ln RH ratios (H14/H3) for AR (Fig. 1A) and TW (Fig. 1B) populations. Dashed lines represent the 95% confidence interval of the standardized normal distribution.

Between generations 14 and 40, corrected Ln RH values are not significantly different across loci either for TW or AR populations (one-way ANOVA; p > 0.05), though they were significant in our previous analysis for the AR data. Standardized Ln RH values for dsub14 fall outside the 95% confidence interval for AR₂ (p < 0.04) and outside the 90% marginal confidence interval for AR₁ (p < 0.06) – see Fig. 2, in contrast with the significant deviations previously reported for all AR populations [1].

Figure 2.

Standardized Heterozygosity ratios (Ln RH) between generations 14 and 40. Ln RH ratios (H40/H14) for AR (Fig. 2A) and TW (Fig. 2B) populations. Dashed lines represent the 95% confidence interval of the standardized normal distribution.

A new analysis that includes the wider range of generations analyzed (40 versus 3, Fig. 3) indicates a significant deviation pattern for locus dsub14 in all AR populations (p < 0.02 for AR₁; p < 0.03 for AR₂ and AR₃), the TW₃ population (p < 0.03), and a marginally significant deviation for TW₁ (p < 0.07). Furthermore, as we already stated in our paper, the high Ln RH values in locus dsub14 were caused by the increase of an initially low-frequency allele in all populations analyzed, which is an observation in favour of positive selection acting near this marker.

Figure 3.

Standardized Heterozygosity ratios (Ln RH) between generations 3 and 40. Ln RH ratios (H40/H3) for AR (Fig. 3A) and TW (Fig. 3B) populations. Dashed lines represent the 95% confidence interval of the standardized normal distribution.

In general, we conclude that our main findings regarding the action of positive selection in our study hold, since our data is still suggestive of a deviation from neutral expectations in locus dsub14, although the signal is less pronounced than reported before. Nevertheless, as previously concluded [1], more studies should be conducted in this specific microsatellite locus (and neighboring areas) to further elucidate the evolutionary forces acting on this specific region of the O chromosome.

We regret any inconvenience that this error in our data might have caused the readers.