FRANKFURT, Dec 18 (Reuters) - A Columbia University economist has become an unwitting victim of the unravelling of Rene Benko's real estate empire Signa, as the ripple effects of Europe's biggest property bust widen.

Gernot Wagner, a climate economist at Columbia's business school, was hired to speak in August at a conference sponsored by Signa in the Austrian alpine village of Alpbach.

The lecturer never got paid - an illustration of the depths of Signa's troubles.

The holding company of Signa - a group of some 1,000 companies, and an owner of New York's Chrysler Building and projects in Germany, Austria and Switzerland - filed for insolvency last month with around 5 billion euros ($5.46 billion) in debt.

It was a dramatic stumble in the Austrian conglomerate's two-decade history that underscored the dimming prospects for the broader property sector after a surge in interest rates and construction costs.

A string of Signa subsidiaries has since followed suit with their own insolvency filings, and more are expected. Meanwhile, founder Benko, one of Europe's most prominent property tycoons, was removed from a ranking by Forbes of the world's billionaires, and a top deputy was hastily fired.

On Tuesday in Vienna, a court-appointed administrator will give an initial assessment of whether Signa's financial and restructuring plans are realistic.

Investors, city planners, construction firms, bankers and regulators - as well as individuals like Wagner - have been trying to come to grips with the ramifications of Signa's demise.

"I should have received 12,000 euros from Signa Holding ... I never received the money," Wagner said.

Signa didn't respond to a request for comment.

The lecturer is among hundreds of companies and individuals that the Signa holding company owes money to, according to a document seen by Reuters.

Another is Ernst & Young, which advised on taxes and compliance matters for a six-digit figure in fees this year, some of which is still outstanding, according to a person with knowledge of the matter.

Signa also owes money to the law firm that advised it on some of its biggest deals, including the Chrysler Building purchase, according to the document. The firm, McDermott Will & Emery, didn't respond to requests for comment.

The turmoil comes amid the biggest property crisis in decades in Germany, Signa's most important market.

For years, the property sector in Germany and elsewhere in Europe boomed as interest rates were low and demand strong.

But a sharp rise in rates and costs has put an end to the run, tipping developers into insolvency as bank financing dries up, deals freeze and prices fall.

A number of Signa projects, including construction on a skyscraper, have been halted.

Earlier this month, the holding company's insolvency administrator said it would immediately discontinue non-essential operations, forcing the dismissal of dozens of employees who oversaw things like hunting, flights and event management.

Meanwhile, Columbia's Wagner is waiting for Benko to pay up.

"In case you reach him, ask him whether he has 12k euros left somewhere," Wagner wrote in an email exchange. ($1 = 0.9158 euros)

(Writing by Tom Sims; Editing by Sabine Wollrab, Miranda Murray and David Evans)