ORONO — The University of Maine Alumni Association Board of Directors has selected Thomas G. Peaco as the organization’s next president and CEO, effective July 5. He will succeed John N. Diamond, who is retiring after leading the 110,000-member association for the past seven years. A longtime Rockland resident and community leader, Peaco currently serves as president and CEO of the Penobscot Bay Regional Chamber of Commerce, which serves over 750 businesses and organizations in the Camden-Rockland region.