A few days after joining the board of Atlantic Power, private equity veteran Gilbert Palter said he got a flurry of calls from the energy company’s top shareholders, who wanted more than just to wish him well. The rising power of activist shareholders has added a new responsibility to the role of board director at a publicly traded company: investor relations. From JPMorgan Chase & Co to Microsoft, and Johnson & Johnson to Apache Corp., board directors across North America have increasingly begun serving as a bridge between institutional investors and corporate management teams.