Life‐History Variation in Contrasting Habitats: Flowering Decisions in a Clonal Perennial Herb (Veratrum album)

Abstract

Quantifying intraspecific demographic variation provides a powerful tool for exploring the diversity and evolution of life histories. We investigate how habitat-specific demographic variation and the production of multiple offspring types affect the population dynamics and evolution of delayed reproduction in a clonal perennial herb with monocarpic ramets (white hellebore). In this species, flowering ramets produce both seeds and asexual offspring. Data on ramet demography are used to parameterize integral projection models, which allow the effects of habitat-specific demographic variation and reproductive mode on population dynamics to be quantified. We then use the evolutionarily stable strategy (ESS) approach to predict the flowering strategy-the relationship between flowering probability and size. This approach is extended to allow offspring types to have different demographies and density-dependent responses. Our results demonstrate that the evolutionarily stable flowering strategies differ substantially among habitats and are in excellent agreement with the observed strategies. Reproductive mode, however, has little effect on the ESSs. Using analytical approximations, we show that flowering decisions are predominantly determined by the asymptotic size of individuals rather than variation in survival or size-fecundity relationships. We conclude that habitat is an important aspect of the selective environment and a significant factor in predicting the ESSs.Keywords: demographic variation, evolutionarily stable strategy (ESS), integral projection models, monocarpic ramets, population dynamics, reproductive mode. Understanding how different patterns of demographic variation drive the establishment and evolution of life histories is one of the main goals of evolutionary ecology (Fox et al. 2001). Most animal and plant species can be found in a wide range of ecologically distinct habitats, and as a result, individuals of the same species may experience substantial variation in demographic rates, such as survival, growth, and fecundity. These demographic heterogeneities between individuals or groups of individuals can have considerable population dynamical consequences and can generate evolutionary change (e. The role of demography as a driving force in life-history evolution is widely recognized, yet relatively few studies have quantified how demographic rates, and consequently life-history traits, vary among individuals and populations of the same species (but see, e.g., Bronikowski et al. 2002;Dorken and Barrett 2003;Frederiksen et al. 2005;Lesica and Young 2005). Instead, much of our knowledge about the diversity and evolution of life histories comes from comparative analyses at the interspecific level. This is surprising, given that intraspecific variation allows the study of ecological constraints on life histories without the confounding effect of phylogeny (Frederiksen et al. 2005). Moreover, across-species comparisons, which are often based on only a limited number of populations per species, m...

Adaptation of the Long-Lived Monocarpic Perennial, Saxifraga longifolia to High Altitude

“…Clonal growth, thus, constitutes an additional process operating at the individual level in terms of enhancing survival, which could also help to explain the lower mortality rate of this population compared to the other ones. The particular habitat or environment has been shown to be an important selective factor in predicting the evolutionary stable reproductive strategy in natural populations of monocarpic plants (Hesse et al, 2008), and S. longifolia constitutes a clear example of reproductive strategy variability along an altitudinal gradient.…”

Evolutionary demography of iteroparous plants: incorporating non-lethal costs of reproduction into integral projection models

“…The development of demographic tools, especially continuously size-structured integral projection models (IPMs) [6,7], has allowed for the estimation of this optimum and quantitative comparisons of observed and optimal reproductive strategies in semelparous plants. We have now accumulated a wealth of such studies [8][9][10][11][12][13][14][15][16][17][18][19]. The popularity of semelparous plants for the study of life-history evolution and reproductive delay is due in part to the ease and elegance with which lethal costs of reproduction can be incorporated into demographic models: the probability of survival is simply conditioned on the probability of not flowering.…”

“…Our goals were to (i) quantify costs of reproduction using long-term demographic data, (ii) incorporate reproductive costs into a demographic model, and (iii) use the parametrized model to predict optimal (evolutionarily stable, ES) reproductive strategies, including size at reproduction and size-dependent reproductive effort. Consequences of reproductive costs depend greatly on demographic context (background rates of growth and survival) and may differ between environments, if demographic rates also differ between environments [10,17,18,35]. We therefore contrasted selection on life histories in two habitat types that are known to be associated with different demographic rates: open (light) and forest understorey (shade) habitats.…”

Plant-soil feedback as a mechanism of invasion by Carpobrotus edulis

“…nutrient and water availability, photoperiod, etc.) can induce clonal plants to allocate resources for vegetative growth or sexual reproduction (Bai et al 2009;Hesse et al 2008). The physiological changes that trigger sexual reproduction can also be affected by different soil organisms (Perner et al 2007) and, therefore, plant-soil feedback may play an important role in determining these reproductive shifts.…”