All organisms face trade-offs in how resources are allocated during a lifetime. For example, a juvenile tree growing in the understory of a closed-canopy forest accumulates carbohydrates via photosynthesis. Those carbohydrates could be used to make new leaves, or instead, they could be stored for future use, or used to synthesize defensive compounds. The evolutionary responses to these unavoidable trade-offs have produced a range of species’ life history strategies. I will discuss the mechanistic basis for trade-offs in resource allocation that individual tropical trees make, how variation in resource availability affects those trade-offs, and how trade-offs at the individual level affect the distribution and diversity of tree species along environmental gradients in Bornean rain forest.