Paper Boat Creative/Getty ImagesPaper Boat Creative/Getty Images AI theme is strong, "long-tailed" and not just a tech story, according to Bank of America's head of US equity and quantitative strategy. Companies across industries are going to have to spend on AI "just to stay alive", Savita Subramanian told CNBC. "AI is just part of this whole efficiency, automation, 'doing more with less' theme that I think is going to be really bullish for corporate margins," she said. The frenzied rally in some artificial intelligence-related stocks this year hasn't been rational, but the underlying AI theme itself is strong, for the long-run, and not just a tech story, according to Bank of America's head of US equity and quantitative strategy.Companies across industries are going to have to invest in AI just to stay competent - and that makes it a broader theme than just a tech story, Savita Subramanian told CNBC on Tuesday."AI is complicated but it's not just a tech story, which is what's exciting about it.