Fidelity Investments announced yesterday that Stephen Jonas, the executive director of Fidelity’s investment management unit, is stepping down at the end of the month after two years on the job.

Jonas and the Boston-based mutual funds company are parting on amicable terms, both sides said.

Jonas has led Fidelity Management and Research Co. since May 2005 when he took over from Abigail Johnson. Johnson, the daughter and possible successor to chairman Edward Johnson, left the post top take over Fidelity’s retirement services unit.

Jonas said he is leaving to spend more time with his family and to pursue some non-profit work after two decades at Fidelity.

Fidelity said vice chairman and COO Robert Reynolds would continue as president of Fidelity Management & Research Co., overseeing the senior team and carrying on the reorganization work begun by Jonas and the team.

Reynolds said the senior FMRCo team of Walter Donovan, Boyce Greer and Dwight Churchill would be realigned to take full advantage of the experience of each. He said Donovan would be president of the equity division, Greer president of the fixed-income division, and Churchill president of investment services.

Fidelity is the parent of Fidelity Investments Canada Ltd. In December, Fidelity Canada announced the departure of renowned fund manager Alan Radlo after 17 years with the firm.