Fig. 1
![Fig. 1](http://media.springernature.com/full/springer-static/image/art%3A10.1186%2Fs12864-016-2986-6/MediaObjects/12864_2016_2986_Fig1_HTML.gif)
Simplified phylogeny of some gonochoric and hermaphroditic unionoid bivalves redrawn after Breton et al. [16]. The presence of DUI (Doubly Uniparental Inheritance) with F- and M-type mtDNAs in gonochoric species is indicated in black, whereas hermaphroditism with SMI (Strict Maternal Inheritance) is indicated in red. Species in black have F-ORFs containing one predicted transmembrane (TM) helix in their N-terminal portion, whereas hermaphroditic species have macromutated H-ORFs with repeat units and sometimes more than one predicted TM helix [16]