Abstract
This paper uses an individual-based modelling approach to explore the effects of genetic tradeoff across a spatial gradient. Tradeoff is represented by the ability of an individual to live at higher environmental values - individuals that can live at high values can also live at low values, but the cost for this generalised ability is an increased time to breeding maturity. This paper shows that for very low tradeoff gradients significant zones still occur across the environment, with a pronounced set of heterozygotic bands. It is proposed that these bands represent hybrid zones, and that the model demonstrates that weak tradeoff across an environmental gradient can produce isolated genetic individuals. This model therefore shows one mechanism leading to parapatric speciation.