So I discovered today that if you send a colony ship to colonize a colony that already exists, it "bolsters" the existing colony. I gained at least one society level by doing it, maybe 2.
BM Forum Name Dave's Galaxy Name Capital Planet Location ID
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Adriddae Vistuvis 1667.4 , 1912.8
Daycryn Kazhaar 1724.1 , 1870.0
De-Legro Masdus
egamma egamma 1661.9 , 1768.6
fodder fodder 1920.9 , 1834.9
Huntsmaster Agiri 1823.2, 1868.5
Kai Kai
Lorduck Lorduck 1693.3 , 1798.8
Nathan Klingzog 1664.2 , 1677.4
Sacha Amaury
Silverfire KingDante
Squishymaster Squishymaster 1912.4 , 1801.4
Tom Balanuir
Vellos Vellos
(added mine)