The effect of the process of star formation on the temporal evolution of the WR and O-type star populations in the Solar Neighbourhood

A comparison between the observed O-type star and the WR star populations and the theoretically predicted ones depends on the effects of stellar wind mass loss during various phases and rotation on stellar evolution and, last not least, on the effects of binaries. Obviously, both populations depend on the massive star formation rate. In the present paper we show that the rate in the Solar Neighbourhood is fluctuating on a timescale which is smaller than the evolutionary timescale of a massive star. We demonstrate that this fluctuating behaviour affects both population enormously, in such a way that a comparison between observations and theoretical prediction to test stellar evolutionary models is ambiguous.