Mitochondrial genome skimming
As cells contain multiple copies of the mitogenome versus one copy of the nuclear genome, enrichment bias can be expected upon including both nuclear and mitochondrial targets in joint enrichment. Considering this issue, we aimed to recuperate mitochondrial data via genome skimming. We recovered on average ~40% of the length of the mitogenome per specimen with a depth between 1× and 300×, which allowed us to reconstruct the entire maternally-inherited Coelaturini mitogenome. This mitogenome revealed the type UF1 gene order, which would have characterised the most recent common ancestor of Unionidae and which is conserved in the subfamilies Ambleminae, Unioninae, but not in Gonideinae (Froufe et al., 2020). No members of Parreysiinae have been subjected to mitogenomic analyses, but our results show that the UF1 gene order prevails in this subfamily, or at least in Coelaturini. Beyond the position of tRNA H and D, this gene order is also highly similar to that of the unionid male mitogenome (Lopes-Lima, Fonseca, et al., 2017).