Who were the olive tree, fig tree, and the grapevine in Jotham’s parable?

NIV Judges 9: 7 When this was reported to Jotham, he climbed to the top of Mount Gerizim, raised his voice, and cried out: “Listen to me, O leaders of Shechem, and may God listen to you. 8One day the trees set out to anoint a king for the…