Google’s (GOOG) Android operating system continues to dominate the smartphone market, but much of its growth is coming from modified, or “forked,” versions of the free-to-use, open-source software. The trend is significant for Google (GOOG) because those forked versions of Android do not offer Google’s services, which impacts Google’s ability to monetize the Android ecosystem, says ABI Research analyst Nick Spencer. In a report Wednesday, ABI said Android was used in 77% of smartphones shipped worldwide in the fourth quarter. But of those 221.5 million Android handsets, 32% used forked versions. A year earlier, forked Android, also called Android Open Source Project (AOSP), versions made up 20% of the total. In Q3, AOSP accounted for 27% of Android handsets shipped. AOSP handset shipments rose 137% in Q4 2013 vs. Q4 2012, compared with 29% growth for Android, ABI reported. In its report, ABI suggests Google could be losing control of the Android ecosystem. Much of the growth in forked Android phones is coming from China, India and adjacent markets, ABI said. Apple (AAPL) is a distant No. 2 in smartphone market share, garnering 18% in Q4. That’s up from 15% in Q3, thanks to the release of the iPhone 5S, ABI says. But its share is down from 23% in Q4 2012, as growth has shifted to emerging markets. “Apple continues to avoid a low-cost smartphone product to target these markets, focusing instead on its traditional premium segment, where growth is harder to achieve due to fast-approaching market saturation,” Spencer said.