FIGURE 1: Map showing the grouping of sequences from the fish species Gasterosteus gymnurus (Cuvier, 1829; a junior synonym ofGasterosteus aculeatus , Linnaeus, 1758) into a single “population” to measure change in intraspecific genetic diversity. This is one of the 909 time-series datasets in Millette et al. (2020). This time-series consists of 53 mitochondrial cytochrome c oxidase subunit 1 (COI) sequences collected at 24 different sampling sites (colored dots). The sampling sites are all within the 1,000 km distance threshold set by Millette et al. for being pooled into a population, despite being located in nine watersheds from six of the major hydrographical regions in France. Sample sizes are highly uneven across the time series, with just three sequences from a single site each in 2004, 2007 and 2009, and then 44 sequences from 21 sites in 2013. Millette et al. (2020) analyzed the trend in nucleotide diversity across these temporal points, despite the 2013 sample consisting of sequences pooled across many different regions, while the other years had a single site, in different regions.