By Mitch Phillips RIO DE JANEIRO, Aug 18 (Reuters) - Alistair Brownlee won the Olympic triathlon in dominant style on Thursday, outrunning brother Jonny in a British 1-2 to become the first to retain the title and underlining his position as the greatest-ever exponent of the swim-bike-run sport. Jonny, 26, third in London four years ago, went one better to take silver after being outkicked by his 28-year-old brother in the heat of the concluding 10km run, with Henri Schoeman taking the bronze, South Africa's first medal in the sport since it was introduced in 2000. The brothers delivered a textbook performance after coming out of the 1.5km sea swim off Copacabana beach and controlling the 40km bike leg. More...