Google and Apple’s combined share of the global smartphone market has doubled in the course of the last twelve months, new research from Gartner has found.

The proportion of smartphones shipped during the second quarter of this year that were based on either Android or iOS was just under 62%, up from 31% in the same period of 2010.

Echoing a recent report from market research firm Strategy Analytics, Gartner found that the proportion of smartphones based on Nokia’s Symbian operating systems dropped precipitously in the last year, from 41% down to 22%.

BlackBerry maker RIM, meanwhile, saw its share of the smartphone market fall from 19% last year to 12%.

"Google and Apple are the obvious winners in the smartphone ecosystem," Gartner said of the findings. "Analysts observed that these two [operating systems] have the usability that consumers enjoy, the apps that consumers feel they need, and increasingly a portfolio of services delivered by the platform owner as well."

Smartphones sales rose 75% year-on-year and represented 25% of the total mobile phone market.

Combined, global mobile device sales hit 428.7 million units during the period, up 17% from the second quarter of 2010. That represented an acceleration in growth, as unit sales increased 14% between the 2009 and 2010.