The timing of the news immediately triggered speculation that Boullier could be heading to McLaren, who were due to launch their 2014 car later in the day in an online presentation.
McLaren, who had a miserable 2013 season without a single podium finish, have yet to say who will lead their team after Martin Whitmarsh lost his position of overall group chief executive to his returning predecessor Ron Dennis.
Whitmarsh has been silent following last week's "coup", with other senior McLaren employees quoted in press releases since then.
"Gerard Lopez, will combine his position on the board with the role of Team Principal with immediate effect," Lotus said in a statement that barely mentioned Boullier other than to thank him for his four-year contribution in the final paragraph.
Lotus were successful on track last season but struggled financially off it, with talk of significant investment from the Middle East that never materialised.
Despite the cash flow problems, they won with Kimi Raikkonen in Australia and finished fourth overall and ahead of McLaren.
Boullier played a major part in keeping the ship steady, appearing as the public face of the team with constant reassurances that all would be well.
He was also instrumental in signing Venezuelan Pastor Maldonado, who brings substantial backing from his country's state oil company PDVSA, from Williams as replacement for Raikkonen who had complained about not being paid his wages.
However, they have lost a number of key technical staff to other teams in recent months.
Lotus are also yet to confirm the renewal of their engine partnership with Renault, although that is taken as a given, and are the only team to have said they will not attend next week's opening pre-season test in Jerez, Spain.
That test is considered particularly important, given significant rule changes, as the first chance for teams to try out on track the new V6 turbo engine and its complex energy recovery systems.
Lotus explained the change at the top as a strengthening of its management structure and to "further increase Genii's role in the team and to close the gap between its strategic, commercial and sporting activities".
Lopez is chairman of Luxembourg-based Genii Capital, who control Lotus - the former championship-winning Renault team.
His chairmanship responsibilities at Lotus will be shared with Andy Ruhan, a British property investor who joined the board last year.
Lotus said they would announce new commercial partners and sponsors when they unveiled their new car in Bahrain next month at the second pre-season test.
"The team will also confirm its organisational structure for 2014 ahead of this test. The team management, car and partner portfolio will illustrate the team's will and desire to continue its quest to become one of the strongest teams in Formula One in every sense," they added.
Image: Gerard Lopez (right) with Eric Boullier.
Photograph: Mark Thompson/Getty Images
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