A dispute over state funding of Florida pubcasters has prompted Miami’s WLRN to create a new system for sharing news stories among pubradio stations. Eight stations serving the state’s largest markets have signed onto the Florida News Exchange, a digital network for content sharing that the Miami station launched in September. It’s modeled after the Northwest News Network, a reporting collaborative of stations in Washington, Oregon and Idaho. Its formation is a direct challenge to the Florida Public Radio Network operated by WFSU in Tallahassee, the state capital — the only Florida pubcaster to be spared from a complete loss of state funding this year. So far the Miami station is the only one to drop its use of that news service, which charges an annual fee of nothing.