History, evolution and future of arctic and alpine flora: overview

The present-day arctic flora replaced Arcto-Tertiary forest when global temperatures dropped markedly towards the end of the Pliocene 3-4 million years ago. During the Quaternary (from 1.8 mya) recurrent cycles of ice ages (glaciations) interspersed with shorter warmer periods (interglacials) have caused arctic and alpine plants to experience frequent range fragmentations and expansions. The application of molecular phylogenetic and phylogeographic analysis, along with an accumulating body of pollen and macrofossil evidence, is providing a greater understanding of the nature and effects of these events. To report what is new in this regard and also to assess what changes might lie ahead as a result of rapid climate warming, a Botanical Society of Scotland Symposium was held in June 2007 at the University of St Andrews on the History, evolution and future of arctic and alpine flora. This special issue contains papers based on presentations given at this meeting. Its aim is to highlight the fusion of recent fossil, molecular and ecological evidence that has advanced our understanding of events that moulded the origin and composition of arctic and alpine floras. In addition, a brief assessment is made of the future of these floras in a rapidly warming world.