Iain Dale has a post today entitled: "Why Don't the LibDems Select BME Candidates in Winnable Seats?". He makes the argument that the Conservatives have BME candidates in a number of winnable seats and estimates they will have between 11 and 16 BME MPs after the next election. He suggests there will be none on the Lib Dem benches.
With STV and multi-member constituencies, parties have a powerful electoral incentive to present a balanced team of candidates in order to maximise the number of higher preferences that would go to their sponsored candidates. This helps the advancement of women and ethnic-minority candidates, who are often overlooked in favour of a 'safer' looking candidate.