(a) Data collection
For our mitochondrial π dataset, we compiled 1781 population-level measurements of genetic diversity, while for Hdwe compiled 1871 diversity measurements. Collectively, these observations came from 239 studies and represented 262 species in 82 families. For microsatellites, we recorded genetic diversity (He ) from 3210 populations, 578 studies, and 341 species in 86 families. When recorded for the same population, nuclearHe was not strongly correlated with either mitochondrial π or Hd(He -π rs = 0.242;He -Hd rs = 0.349) although π and Hd were positively related to each other (π-Hd rs = 0.818) (Fig. S1).
These nuclear and mitochondrial datasets represented populations from across the globe, spanning all latitudes, every ocean basin, and a wide array of environmental conditions (Fig. 1, S2 & S3). Coastlines in the Northern hemisphere represented the most densely sampled regions in our database. However, there were still a large number of diversity estimates near the Equator, particularly in the Coral Triangle. While the number of datapoints decreased towards the poles for both mitochondrial and nuclear diversity, there were still a substantial number of diversity estimates at latitudes greater than 60° N or S for both mitochondrial (39 observations) and nuclear (311 observations) diversity.