Andy Rubin has stepped down as the executive in charge of Google's Android operating system for smartphones and tablet computers, ending a seven-year reign that reshaped the technology industry.

The unexpected change announced Wednesday may raise new questions about Android's direction as Google duels with Apple Inc., Microsoft Corp. and a long list of other companies in the increasingly important mobile computing market.

Google is replacing Rubin with Sundar Pichai, an executive in charge of the company's Chrome Web browser and operating system for lightweight laptop computers. That move may heighten recurring speculation that the Chrome operating system eventually will supplant Android. Google executives so far only have said they want to make sure the two operating systems can operate cohesively together.

Pichai is a logical choice to succeed Rubin because there is probably going to be even more "natural confluence" between the Android and Chrome systems in the next few years, said Edward Jones analyst Josh Olson.