* Federer and Wawrinka put Swiss 2-0 ahead against Serbia * Kohlschreiber and Mayer give Germany lead over Spain * Czech holders level with Dutch, France dominate Australia * Britain lead U.S. after Murray beats replacement Young (Adds details on Czech tie, other results) By Toby Davis LONDON, Jan 31 (Reuters) – Roger Federer and Stanislas Wawrinka gave Switzerland a 2-0 lead over last year’s runners-up Serbia while injury-hit Spain trailed Germany by the same margin as the Davis Cup World Group first-round ties got underway on Friday. Serbia fielded a second string team without world number two Novak Djokovic, two months after they lost to the Czech Republic in the final, and were quickly under pressure in Novi Sad.