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).