Andy Wightman, a well-known campaigner for land reform before entering politics, will now sit as an independent until next year's Holyrood election.
In a letter to Greens co-leaders Patrick Harvie and Lorna Slater, he said was "saddened by the intolerance shown by some party members to an open and mature dialogue about the tensions and conflicts around questions of sex and gender in the context of transgender rights and women’s rights".