Print PageSize is the most suitable proxy for studying the ecology and evolution of modular organisms, such as higher plants. An excellent understanding has been achieved on the anatomical, physiological and demographic mechanisms that control and promote plant growth. In contrast, the factors that contribute to plants decreasing in size, as well as the demographic implications of plant shrinkage, remain unknown.
We examined plant shrinkage in a natural setting, within the context of projected precipitation increases in the Great Basin desert, through a long-term (2006-2010) demographic study of the native desert chamaephyte Cryptantha flava (Boraginaceae). We simulated precipitation pulses of 4.5 cm every August from 2006 to 2009 and explored the demographic dynamics of >3500 individuals at two levels. At the individual level, we used integral projection models and applied life table response experiment (LTRE) analyses to discern the effect of natural vs. simulated precipitation and elasticity analyses to explore the importance of individual’s growth and shrinkage. Within individuals, we studied the effects of plant shrinkage -whereby whole patches of leaf rosettes die at once, but the whole individual remains alive- on the demographic dynamics of the remaining rosettes.
Results/Conclusions
Individual-level demographic analyses revealed a carry-over effect of the watering treatment: the population growth rate increased up to two years after the treatment. LTRE analyses indicated that such increases were attributable to the ability of individuals to change drastically in size: growing when the environment was beneficial, and shrinking when adverse. Furthermore, elasticity analyses revealed that only medium-size individuals contributed significantly to the population growth rate. The observed size distribution after dry years was much closer to the stable size distribution than size distributions after wet years. This phenomenon is due to the ability of plants to shrink during dry years. Within individuals, the remaining patches of rosettes experienced an increase in their probabilities of survival and reproduction the year after a patch of rosettes had died.
Our study suggests that climate change might actually bring benefits to the population dynamics of the native C. flava. Such benefits are mediated by the plant’s modular construction, which allows it to quickly re-adjust its size to the ever-changing conditions typical of deserts. Furthermore, our study also adds evidence that decreasing in size by the death of a patch of rosettes relaxes competition among the remaining rosettes of an individual.
