By John L. Pitts Daily Journal TUPELO – This year’s Gum Tree 10k represents a special milestone for the race, which starts and finishes in downtown Tupelo. May 13 will mark the 40th running of the Tupelo Running Club event, held annually since its founding except for a schedule-related hiatus in 2005. “It’s always an exciting time in the city of Tupelo,” mayor Jason Shelton said Tuesday at a news conference.