A comparison of life-history characters of arctic and alpine populations of the annual Koenigia islandica

Temperature limits biological activity in tundra environments. Because of the gradients of latitude and elevation along their extensive range, however, many differences in environmental characteristics exist among arctic and alpine tundra ecosystems. Species inhabiting both environments are expected to adapt to this range of environmental conditions by evolving either ecotypes or phenotypically plastic populations.; Annual plants are rare in tundra environments because of having to complete their entire life cycle in a short, cold summer. The few annual species that grow in these harsh habitats reveal a number of prominent characteristics, such as very small habit, rapid development and low temperature optima for growth and reproduction. Yet, despite the theoretical importance of their biology and ecology, arctic and alpine annuals have been little studied.; This study focuses on dissimilarities between arctic and alpine environments, and corresponding evolved differences in germination characters, morphology, phenology and life histories of six arctic and alpine populations of the widely distributed arctic-alpine annual Koenigia islandica L.; Striking dissimilarities, suggesting ecotypic differentiation among the six populations, were found in all studied traits, including temperature and light requirements for seed germination, as well as the effect of winter-like cold treatment (stratification) on germination. Morphology, phenology and life-history characters were also found to be strikingly dissimilar among the six populations of K. islandica grown in simulated arctic and alpine conditions. On the basis of phenology, the six populations can be clearly grouped into arctic, high latitude alpine and alpine populations: arctic plants develop and flower earliest, and alpine plants latest. Populations from high latitude sites and one alpine population performed better in arctic conditions, whereas the lowest latitude alpine population and, surprisingly, a high arctic population showed no enhanced performance under simulated arctic conditions.; Arctic and alpine populations of K. islandica offers a unique opportunity to gain insight into divergent life-history strategies found within species, and provides evidence for strong ecotypic differentiation. Furthermore, the dynamics of this extreme heat-intolerant species makes it ideal for use as a tool in the study of global climate change.