Investec's shares dropped lower on Thursday after the specialist bank and asset manager revealed that trading since the end of the last financial year has been tougher than expected."Against a backdrop of poor economic fundamentals and weak debt and equity markets, operating conditions have been more difficult than anticipated in the first quarter of the group's 2012 financial year," the firm said.However, Investec highlighted that operating profits before tax were still marginally ahead of the first quarter of 2010. Core loans and advances grew by 3% to £19.4bn over the three month period, while customer deposits increased b2% to £24.9bn. Third party assets under management rose 2% to £91bn.While the Asset Management and Wealth Management businesses have performed well, driven by increased average funds under management and net inflows, earnings at the Specialist Banking businesses have been under pressure. Nevertheless, the units have seen a growth in margin and fee income, the firm said.Shares fell 2.76% to 479.1p at 11:52.BC