A French tourist captured in North Africa by a group aligned with the Islamic State is seen beheaded in a video circulated on Wednesday, according to SITE Intelligence, which tracks jihadist groups. The Frenchman — Hervé Gourdel, a 55-year-old mountaineering guide from Nice — was abducted in Algeria on Sunday by the terrorist group, known as Jund al-Khilafah. Mr. Gourdel had arrived only a day before on a trip to go hiking in Algeria’s northern mountains.