The Eaton Vance Global Macro Absolute Return Fund, the firm’s flagship alternative mutual fund, will close to new investors on Oct. 1 because of capacity constraints.

The fund, which opened in 2007 and is managed using a hedge fund strategy, had $6.4 billion as of Aug. 31, confirmed spokeswoman Robyn Tice.

“We are closing the fund because we believe doing so is in the best interest of shareholders. Investments in frontier markets are an important element of the fund’s investment program that constrain its capacity,” Payson Swaffield, chief income investment officer, said in a news release.

Ms. Tice said Eaton Vance will “soft-close” the fund on Oct. 1, allowing existing clients, including 401(k) plans, to continue to invest additional money. The fund may impose further restrictions or may open the fund again to new investors, Ms. Tice stressed.

Eaton Vance introduced a fund using a similar strategy, the Global Macro Absolute Return Advantage Fund, on Sept. 21. The new fund invests less in frontier markets than the original version of the strategy in order to increase the fund’s overall capacity and has higher risk levels.