THE EFFECT OF FLEXIBLE GROWTH-RATES ON OPTIMAL SIZES AND DEVELOPMENT TIMES IN A SEASONAL ENVIRONMENT

The interrelationships among development time, growth rate, and adult size are investigated using simple optimization models of a seasonal l ife history in which larger adults have greater reproductive output. U nlike most previous studies, our models assume that growth rate is an adaptively flexible character that can be increased at the expense of a greater juvenile mortality rate. Three components of fitness are con sidered: the cost of developing at a suboptimal time of the year, the reproductive advantage of larger adult size, and the increased mortali ty from rapid juvenile growth. The study focuses on the optimal respon ses of size, development time, and growth rate to changes in the amoun t of time available for completion of the life cycle. The models show that the optimal growth rate and size at maturity may respond in sever al different ways. Perhaps the most likely effect is that growth becom es faster and size smaller with less time available. It is also possib le, however, for either growth rate or size (but not both) to stay con stant; in other cases, less time available leads to slower growth or l arger size. The effects of increased mortality on the juvenile stage a re also explored; here, the optimal size is likely to decrease, but gr owth rate and development time may increase or decrease.