(b) Mitochondrial diversity
Globally, average mitochondrial genetic diversity was higher in the
western Pacific Ocean and lower along North American and European
coastlines (Fig. 1A & B, Fig. S2A & B). For bothHd and π, diversity peaked at low-to-mid
latitudes and declined towards the poles, particularly in the Northern
hemisphere (Fig. 2A & B, Fig. S4A & B). Diversity was also
consistently higher in the Coral Triangle and elsewhere in the western
Indo-Pacific (Fig. 3A & B). For mitochondrial genetic diversity (eitherHd or π), we found that all latitude and
longitude models performed better than the baseline (null) model (Table
1). Latitude, absolute latitude, and longitude were all significant
predictors of mitochondrial genetic diversity (Table 1, Fig. S5). As
expected, Hd increased consistently with the
length of the locus in basepairs (Fig. S6) and decreased towards species
range edges (although π did not) (Fig. S7).
Except for SST range, all environmental drivers were significantly
correlated with mitochondrial genetic diversity (bothHd and π) and performed better than the null
model (Table 2, Table S2 & S3). Sea surface temperature was positively
related with mitochondrial diversity (Fig. 4, Fig. S8), while
chlorophyll followed a quadratic relationship with diversity highest at
upper-range chlorophyll values (5-10 mg/m3) (Fig. 4,
Fig. S9). Overall, the best-performing models for mitochondrial genetic
diversity (both Hd and π) were mean SST and
maximum chlorophyll.