Global Genetic Change Tracks Global Climate Warming in Drosophila subobscura

Abstract

Comparisons of recent with historical samples of chromosome inversion frequencies provide opportunities to determine whether genetic change is tracking climate change in natural populations. We determined the magnitude and direction of shifts over time (24 years between samples on average) in chromosome inversion frequencies and in ambient temperature for populations of the fly Drosophila subobscura on three continents. In 22 of 26 populations, climates warmed over the intervals, and genotypes characteristic of low latitudes (warm climates) increased in frequency in 21 of those 22 populations. Thus, genetic change in this fly is tracking climate warming and is doing so globally.

The chromosomal polymorphism of Drosophila subobscura: a microevolutionary weapon to monitor global change

“…It was negatively correlated with latitude and increased over the sample period in 22 of the 26 localities (12 out of 13 in Europe, 5 out of 6 in South America and 5 out of 7 in North America), indicating that temperature had, in fact, increased at most sites. Most interestingly, the changes in the Chromosome Index paralleled those of the Temperature Index in 22 of 26 cases (Rayleigh test, Poo0.001), consistent with the hypothesis that the changes observed in the inversion polymorphism of D. subobscura were driven by the changes in temperature (Balanyà et al, 2006, Table 1 and Figure 2 …”

“…These long term changes detected in the chromosomal polymorphism of D. subobscura in three discontinuous areas match those expected to take place in response to global warming. Balanyà et al (2006) decided to test more directly whether climate and chromosomes were, in fact, shifting in parallel. They first used a principal component analysis to combine arrangement frequencies into a single Chromosomal Index (the first principal component), which explained 45.8% of the total variability.…”

“…To find out Balanyà et al (2006) computed the first principal component for weather data, using the mean monthly minimum and maximum temperatures at the nearest weather station for each sample locality. The first principal component, explaining 79.8% of the variance, was the Temperature Index.…”

Gene flow and gene flux shape evolutionary patterns of variation in Drosophila subobscura

“…The rich polymorphism in paracentric inversions found in Drosophila subobscura (Krimbas and Powell, 1992;Krimbas, 1993) has had an important role in demonstrating the adaptive role of inversions, as shown by the coinciding latitudinal clines on inversion frequencies found in Palearctic and also in colonizing populations (Krimbas and Loukas, 1980;Prevosti et al, 1988;Balanyà et al, 2003). Moreover, changes in chromosomal polymorphism matching global warming (Solé et al, 2002;Balanyà et al, 2004Balanyà et al, , 2006) also suggest the adaptive value of inversions in D. subobscura. Despite the evidence for an adaptive role of inversions, the genetic and mechanistic basis underlying their role in adaptation remains unknown.…”

“…In D. subobscura, high genetic differentiation between European populations was detected when chromosomal arrangements were used as markers, as their frequency widely varies between populations (Krimbas, 1993). However, given that these chromosomal arrangements are under strong selection (Prevosti et al, 1988;Balanyà et al, 2006), gene flow between populations would likely be underestimated using the inversions themselves as makers. Interestingly, low levels of genetic differentiation between European populations of D. subobscura were observed using molecular markers such as restriction fragment-length polymorphisms (Rozas et al, 1995) and microsatellite loci (Pascual et al, 2001).…”