The children of Israel again did that which was evil in the sight of Yahweh, and served the Baals, and the Ashtaroth, and the gods of Syria, and the gods of Sidon, and the gods of Moab, and the gods of the children of Ammon, and the gods of the Philistines; and they forsook Yahweh, and didn't serve him.
These verses really introduce the judgeships of Jephthah, Ibzan, Elon, Abdon, and Samson (Judges 10:8 to Judges 16:31). Another possibility is that since the introductory formula in these verses is not strictly a sequence indicator, the judgeship of Jephthah may have overlapped Gideon’s somewhat.