Mr Alexander's move is a result of Nikko's Australian fixed income team being subsumed into the global division as a result of mandate changes by major client and former parent company Suncorp.
Two analysts and one portfolio manager will leave the Australian team as a result of the changes.
Other changes within the fixed income team include the addition of John Sorrell and Leo Leslie to the global credit division, and the addition of Darren Langer and Chris Rands to the rates division.
The announcement is the result of a restructure of Nikko's fixed income function which will see the Australian team integrated into the global team.
A statement by Nikko said the decision comes "following the recent news that Suncorp, former parent company of what is now Nikko AM Australia, has decided to reshape its investment strategy and operating model".
Nikko AM finalised the acquisition of Tyndall Investments from Suncorp in March 2011, with the company later rebranded as Nikko AM Australia.
Suncorp, which remains a major client for Nikko AM Australia, announced on Friday morning that its new operating model for its funds under management is "part of a manager diversification program that began two years ago".
Suncorp chief financial officer Steve Johnston said the new strategy, which includes "reviewing investment mandates and finding additional portfolio managers, provides more flexibility in the way the company seeks to manage investment risks and capture opportunities".
"We acknowledge the hard work and commitment of funds manager Nikko Asset Management over the past six years and value our long-standing relationship with them," Mr Johnston said.
As for Nikko AM, the changes to the fixed income team mean that London-based Andre Severino has been appointed as the sole head of global fixed income (leading a team of 13).
Nikko AM Australia managing director Sam Hallinan said, "At Nikko AM, we firmly believe that developed market fixed income solutions are becoming less regionally oriented, and that shared global insight is the key to fixed income alpha. This decision is reflective of that philosophy."
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