Low levels of genetic differentiation with isolation by geography and environment in populations of Drosophila melanogaster from across China

The fruit fly Drosophila melanogaster is a model species in evolutionary studies. However, the population processes of this species in East Asia are poorly studied, even though this area was one of the first regions colonized outside of its native distribution range. Here we examined the population genetic structure of D. melanogaster across China. There were 14 mitochondrial haplotypes with ten unique ones out of 23 known from around the globe. Pairwise FST values estimated from 15 novel microsatellites ranged from 0 to 0.11, with geographically isolated populations showing the highest level of genetic uniqueness. STRUCTURE analysis identified high levels of admixture at both the individual and population levels. Mantel tests indicated a strong association between genetic distance and geographical distance as well as environmental distance. Full RDA analysis showed that independent effects of environmental conditions and geography accounted for 62.10% and 31.58% of the total explained ..., Sample collection and DNA extraction

Specimens of D. melanogaster were collected from 16 locations in China were trapped by using rotten fruits (e.g., grapes, watermelon and banana) in the year 2019 (Table 1; Fig. 1). The sampled flies were firstly checked morphologically using an anatomical lens, followed by molecular identification by BLAST searching of the mitochondrial cytochrome oxidase subunit I (cox1) gene (see below) against the nucleotide database (nt) and in the BOLD system (http://www.boldsystems.org) to ensure the reliability of morphological identification. All samples were stored in 98% alcohol, and frozen at −80 °C before DNA extraction. A DNeasy Blood and Tissue Kit (Qiagen, Germany) was used to extract total genomic DNA individually for 330 samples randomly selected from 16 populations.

Mitochondrial gene amplification and sequencing

To characterize the mitochondrial variation and validate correct identification of the specimens, a fragment of the cox1 gene inv..., Genetic diversity analysis of Drosophila melanogaster.