This post tries to collect information about the concentration of market power with science publishers. If you want to contribute, please leave comments stating who bought whom in which year and a URL giving proof about the deal, in case you have one.
The examples I start with are from linguistics and manl concern German publishing houses.
Niemeyer, Oldenburgh, Akademie-Verlag -> De Gruyter GmbH
Metzler -> Springer
Routledge -> Taylor & Francis (a division of Informa plc, whose biggest investor (7.77%) is BlackRock)
Böhlau (2017) -> Vandenhoeck & Ruprecht
Bonn University Press/Mainz University Press/Universitätsverlag Osnabrück/Vienna University Press -> V & R unipress -> Vandenhoeck & Ruprecht
Blackwell publishing (2007) -> Wiley-Blackwell, owned by John Wiley & Sons, Inc. (publically traded but controlled by the Wiley family via preference shares )