2.1 | Samples and DNA sequencing
We analyzed resequenced whole genome data from 90 S. catenatusindividuals from nine of the populations described in Ochoa et al. (2020) (see Table S1 for population names, codes, and numbers of individuals analyzed, and Figure 1 in Ochoa et al. [2020] for map showing population locations). We also analyzed samples from a population of S. tergeminus from Cheyenne Bottoms, Kansas (Table S1) as a reference for expected patterns of variation in a closely-related yet outbred species (see above).
We used genomic DNA previously extracted from blood samples (see Sovic et al. [2019]) to prepare paired-end (PE) shotgun libraries with 500-bp inserts and to generate PE 150-bp reads using Illumina sequencing platforms. Most samples were sequenced at medium or low coverage (< 15x), but a small number of samples were sequenced at high coverage (> 15x) (see Table S1 for mean coverage statistics for individual samples).