* More consolidation expected in industry - analyst * Couche-Tard shares rise 8.6 pct to record high (Adds industry expert, analyst comments, background; updates shares) By Devika Krishna Kumar Dec 18 (Reuters) - Canada's Alimentation Couche-Tard Inc will buy smaller U.S. rival Pantry Inc for about $861 million, a deal that positions it as one of the top convenience store operators in North America. The deal will add about 1,500 stores to Couche-Tard's network, boosting its presence in the southeastern and Gulf Coast regions of the United States and making it almost as big as 7-Eleven, the world's largest convenience store operator. Couche-Tard's aggressive growth strategy was not surprising, given that the company made an unsuccessful hostile bid for Casey's General Stores Inc in 2010, said Jeff Lenard, spokesman for the National Association of Convenience Stores.