Lineage selection in plasmid evolution
He defines lineage selection as selection for traits which increase the fitness of a group of plasmids, rather than an individual plasmid with in a cell or a particular cell containing plasmids. He says that the unit of selection are "plasmid-host clades" : in other words the unit of selection is the group of closely related plasmids in separate cells. It is an example of a kin-selection though I haven't seen the specific terminology in widespread use. He likely doesn't use kin selection because the plasmids don't have well defined offspring, so he uses a broader term for kin--lineage. I might have preferred clade selection, but this term has its own baggage. I'm not sure (and neither is Paulsson) that kin selection is need to explain 'spitefully low loss' rates, since intra-cellular and inter-cellular selection both favor lower loss rates.