RELATIONSHIPS BETWEEN FLOWERING PHENOLOGY AND LIFE-HISTORY STRATEGIESIN TUNDRA PLANTS

Temperate plants show high correlations between life history strategie s (e.g., along the r-K continuum), mating systems (in terms of pollen: ovule, seed: ovule, and fruit:flower ratios), and genetic population s tructure. In the tundra, nearly all plants would be categorized as bei ng K-strategists if we use life history traits alone (life span, resou rce allocation patterns, etc.). However, there is immense variation am ong species with regard to reproductive traits, such as seed:ovule and fruit: flower ratios, and thus there is a decoupling of the relations hips that are valid in other biota. Instead, the reproductive strategi es of arctic and alpine plants show strong correlations with flowering phenology, and thereby also with snow cover duration. Early-flowering species show high outbreeding rates and low seed: ovule ratios, and m ost of the genetic variation is found within local populations; the op posite situation applies in late-flowering species. These two cases ar e the extremes of a continuum, but arctic plants can be as readily cat egorized in this model as temperate plants are in the r-K model. Gynod ioecious and dioecious breeding systems are abundant only among early- flowering species, whereas apomixis and vivipary are restricted to the late-flowering species. The variation in ploidy levels among species increase from early- to late-flowering. According to the kind of bet-h edging with the resources spent on reproduction, the early- and late-f lowering groups are recognized as pollen-risk and seed-risk strategist s, respectively.