Niche Construction Through Germination Cueing: Life-History Responses to Timing of Germination in Arabidopsis Thaliana

Abstract

Abstract. Germination responses to seasonal conditions determine the environment experienced by postgermination life stages, and this ability has potential consequences for the evolution of plant life histories. Using recombinant inbred lines of Arabidopsis thaliana, we tested whether life-history characters exhibited plasticity to germination timing, whether germination timing influenced the strength and mode of natural selection on life-history traits, and whether germination timing influenced the expression of genetic variation for life-history traits. Adult life-history traits exhibited strong plasticity to season of germination, and season of germination significantly altered the strength, mode, and even direction of selection on life-history traits under some conditions. None of the average plastic responses to season of germination or season of dispersal were adaptive, although some genotypes within our sample did exhibit adaptive responses. Thus, recombination between inbred lineages created some novel adaptive genotypes with improved responses to the seasonal timing of germination under some, but not all, conditions. Genetically based variation in germination time tended to augment genetic variances of adult life-history traits, but it did not increase the heritabilities because it also increased environmentally induced variance. Under some conditions, plasticity of life-history traits in response to genetically variable germination timing actually obscured genetic variation for those traits. Therefore, the evolution of germination responses can influence the evolution of life histories in a general manner by altering natural selection on life-history traits and the genetic variation of these traits.Key words. Dormancy, maternal effects, natural selection, phenotypic plasticity, seasonal cues.Received October 25, 2004. Accepted January 16, 2005 The timing of seed germination is highly responsive to environmental conditions. For a seed to germinate, certain environmental conditions must be present to break dormancy, and additional environmental conditions must exist subsequently to permit germination (Simpson 1990;Bewley 1997;Baskin and Baskin 1998). The timing of germination can therefore be a precise mechanism of habitat selection or niche construction that determines the environment experienced by the plant (Donohue 2003(Donohue , 2005. If the environmental conditions that elicit germination accurately predict the environment experienced by adults, germination behavior has the potential to influence the environment experienced by the plant throughout its life. It can thereby influence the phenotypic expression of plastic postgermination characters and the mode and strength of natural selection on those characters (Donohue 2002).Niche construction occurs when organisms alter the environment they experience (Odling-Smee et al. 1996), either through direct habitat modification, habitat choice, or resource garnering and depletion (Bazzaz 1991; de Kroon and Hutchins 1995;Huber et al. 1999). The environme...

Seed after‐ripening and dormancy determine adult life history independently of germination timing

“…If germination does not occur before the onset of winter, the cold season will induce secondary dormancy. Small differences in the speed of germination, like those observed in our experiment, can have significant consequences for survival and fitness, particularly during the autumn and spring (Donohue, 2002;Donohue et al, 2005a). Selection is thus expected to favor mechanisms that enable seeds to cycle timely in and out of dormancy in response to environmental fluctuations (Vleeshouwers et al, 1995).…”

“…The timing of germination establishes the season in which plants begin their growth, which conditions subsequent survival and phenology, and, in turn, affects the reproductive output of the plant (Galloway, 2001;Donohue et al, 2005a;Wilczek et al, 2009).…”

The effects of the genetic background on herbicide resistance fitness cost and its associated dominance in Arabidopsis thaliana

“…In the same way A. thaliana lines associated with a high seed production in the fall because of adequate germination timing can be counter-selected in spring on account of a delay in germination timing (Donohue, 2002;Donohue et al, 2005). As a result, the dynamics of selection of an adaptive allele might, in turn, depend on the interactions between environment and timing of trait expression.…”

Proteomic Analysis of Seed Dormancy in Arabidopsis

“…In mature seeds, the break of dormancy may either occur gradually in the dry state (after-ripening) or be initiated by imbibition under defined conditions (e.g. cold stratification or chilling at low temperature; Karssen, 1982;Baskin and Baskin, 1998;Koornneef et al, 2002;Donohue et al, 2005;Gubler et al, 2005).…”