Delayed Germination of Seeds: A Look at the Effects of Adult Longevity, the Timing of Reproduction, and Population Age/Stage Structure

Abstract

Abstr.~lc,t.-The effects of adult longevity, the timing of reproduction. and population ageistage structure on the evolution of seed dormancy are explored in both constant and variable environment modcls. In the constant environment modcls complete germination is the cvolutionarily stable strategy (ESS) regardless of adult longevity. Incorporating a cost of reproduction on subsequent survival does not alter this result. In contrast, in a variable environment changes in adult longevity can exert a strong selection pressure against seed dormancy. Incorporating a cost of reproduction for iteroparous species reduces adult longevity, which selects for more seed dormancy. The magnitude of the change in ESS germination probability depends on several factors, including which life-history stage is variable (e.g., fecundity, seedling survival), whether seeds can detect favorable sites for establishment, and the ageistage structure of the population. In general, increases in adult longevity select against seed dormancy, but exceptions to this pattern are discussed. The idea that established plant traits arc uncoupled from those of the regenerative phase, as assumed by J. P. Grime's competition-stress-rude131 model, is considered critically.

Seed bank persistence of clonal weeds in contrasting habitats: implications for control

“…In the third-year, the experimental soil seed banks of both species were nearly depleted, having declined to less than 5% of their original size. Consistent with our results, theoretical models predict that the ability to reproduce by vegetative growth in addition to reproduction by seeds will select for reduced seed dormancy and consequently a rapid decline in the soil seed bank (e.g., Venable and Brown 1988;Rees 1994Rees , 1996Forbis 2003). Alternatively, Meyer and Pendleton (2005) suggested that the presence of only a transient or short-term persistent seed bank could represent a response to long-term selection for germination immediately following a mast year, when predation risk to individual seeds is expected to be reduced.…”

“…Indeed, the ability to reproduce vegetatively in addition to reproduction by seeds is known to be an important feature of alpine plant life (e.g., Kö rner 1999). Life history theory predicts that life history attributes that reduce the impact of environmental variation on fitness such as seed dormancy, adult longevity and vegetative or clonal reproduction, will show patterns of negative co-variation (Rees 1994). According to this pattern, increased adult longevity and adult vegetative spread should select against seed dormancy.…”

The Evolutionary Significance of Seed Germinability in an Alpine Meadow on The Eastern Qinghai-Tibet Plateau

“…mangrove trees) often germinate inside the ripe fruit, while still on the mother plant (Figueroa and Armesto, 2001); however, seeds of many desert plants remain dormant and viable, while buried in the soil for years or decades after dispersal (Venable and Lawlor, 1980). It has been argued theoretically that low germinability would be associated with life history attributes such as seed size (Thompson and Grime, 1979;Venable and Lawlor, 1980;Grime et al, 1981;Venable and Brown, 1988;Rees, 1993Rees, , 1994Cater and Ungar, 2003), seed dispersal mode (Garwood, 1983), longevity of plant (Thompson, 1987), and life form (Figueroa and Armesto, 2001).…”

Spreading recruitment over time to cope with environmental variability

“…Strategies to cope with temporal unpredict-444 ability are expected to be of high importance because 445 strong temporal variation in vital rates like recruit-446 ment has important consequences for life-history 447 evolution and population dynamics (Real 1980;448 Tuljapurkar 1989;Boyce et al 2006). Under such 449 conditions, short-lived plants like P. coronopus are 450 expected to evolve risk-spreading strategies because 451 reproduction occurs only once or twice in their 452 lifetime (Rees 1994 (Venable et al 1987;Cheptou et al 464 2008), and may have a profound effect on the life 465 cycle and population regeneration in the successive 466 years (Mandak and Pysek 2005 Fig. 3 Proportion of apical seeds produced in the inflorescences of P-c population, and early and late emergents estimated to come from them in two contrasted years (see text for further details)…”