Competition for space can drive the evolution of dormancy in a temporally invariant environment

Abstract

I present a model for the evolution of a seed bank in the absence of externally driven environmental variation. I use Evolutionarily Stable Strategy (ESS) analyses of both analytic and simulation models to assess the conditions under which a dormant genotype can invade and resist invasion. In my models, plant seeds compete through lottery for discrete safe sites holding one individual each. Analyzing the conditions under which a dormant genotype can invade when rare and resist invasion once established, I conclude that dormancy can be an ESS when some fraction of seeds is retained locally, seed bank survival is high, and mortality in the seed bank is low. The advantage of dormancy stems from the ability of dormant seeds to recapture a lost site and the fact that a plant's offspring are more likely to win the lottery in its own site than in any new site. The advantage of dormancy does not depend on individual fecundity or on low relatedness with the offspring of kin, making this mechanism distinct from earlier models of sib competition.

Gene-flow through space and time: dispersal, dormancy and adaptation to changing environments

“…Other theoretical studies investigating the evolution of dormancy further support the prediction that, in general, increasing spatial dispersal tends to decrease the evolutionarily stable (ES) ratio of dormant propagules (Kobayashi and Yamamura 2000;Satterthwaite 2010). Several studies analyzing the evolution of spatial dispersal also found that, in general, increasing dormancy selects for lower ES dispersal fractions (Levin et al 1984;Cohen and Levin 1991).…”

Maternal fecundity does not affect offspring germination – An empirical test of the sibling competition hypothesis

“…Consistent with classical plant theory (Grime, 1973) and based on previous results (Holzapfel et al, 2006;Schiffers and Tielbörger, 2006) we assumed that generalised (i.e. inter-plus intra-specific) competition intensity is highest at the productive end of our gradient.…”

“…Knowing from previous studies performed at our sites that competition is a major determinant of annual plant fitness in this system (Holzapfel et al, 2006;Schiffers and Tielbörger, 2006), that our focal species display dormancy fractions that vary in response to several environmental factors (Petr u and Tielbörger, 2008), and that dispersal is negligible (Siewert and Tielbörger, 2010) it was reasonable to assume that in addition to abiotic factors, sib competition should be a major selective force determining seed germination. Because we did not find support for this assumption even in the densely-populated Mediterranean environments, we interpret our results as strong evidence against the sib competition model.…”

“…In a recent model, Satterthwaite (2010) demonstrated that neither environmental variation nor sibling competition is required for the evolution of dormancy in annual plants. In this model, dormancy is explained as a space-holding strategy allowing a genotype greater chances to maintain a site.…”

“…Also, for being able to generalise our findings, we selected species which differed largely in both germination strategy as well as competitive ability, but all of which do have dormant seeds and are negatively affected by competition. Results from previous experimental germination and neighbour manipulation studies (Lampei and Tielbörger, 2010;Petr u, 2006;Schiffers and Tielbörger, 2006), were used to classify species with respect to dormancy and competitive ability (competitive response ability). Biscutella didyma L. (further referred to as 'Biscutella'), a Brassicaceae, has intermediately dormant seeds (30e70%, Petr u, 2006) and is a weak competitor.…”