National Australia Bank continues to build up the portfolio of investment management businesses it owns, or part-owns, through nabInvest.The latest acquisition is Aviva Investors Australia Limited, an active manager of Australian equities and listed property with around A$5.5 billion in assets under management. Aviva Investors produced a net profit of $2.1 million in the year to December 2010, on a turnover of $31 million. The business had net assets of $15 million at the end of 2010, following payment of a dividend of $3 million to its UK-based owner.Aviva will be the twelfth boutique fund manager acquired by nabInvest since it established a funds management "incubator" in 2007.Last month, the business announced the purchase of a stake in Altrinsic Global Advisors, which is based in Connecticut.