Figure 1.

Yearly climate progression across a species' range in the temperate and boreal zones (left) can be often split into two to three main parts: a long winter shouldered by periods of frost events in spring and autumn (ends of bar/blue) and a short growing season with benign conditions (central part/green) at the cold end; a shorter winter with periods of frost and a longer growing season in the range centre; a brief winter and a growing season that is interrupted by a period of hot, dry or hot-dry conditions (very centre/yellow) at the warm end. The dotted lines indicate the relative position of the beginning and end of the benign/growing season. Many other seasonal regions of the world experience a similar pattern of conditions. Accordingly, strategies (right) to cope with the short benign seasons for growth, development and reproduction at the cold and warm end of distribution may involve: avoidance, which requires rapid growth and development, or tolerance of frost and heat and consequently some lengthening of the time for growth and development (inserts/cyan), or resistance to frost and heat and considerable lengthening of the time for growth and development. Mixed strategies are not shown here. (Online version is in colour.)