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Phenotypic Selection on Plant Height in a Segregating Hybrid Population of Crepis tectorum (Asteraceae)

A segregating hybrid population of Crepis tectorum was established at an outcrop site occupied by a short-stemmed population (ssp. pumila) to determine whether selection still favors a prostrate habit in this dry, exposed, and nutrient-poor habitat. Despite extensive variation in the experimental population, there was no apparent trade-off between plant height and head number. Plant stature was positively correlated with intensity of herbivore damage and showed a negative relationship with the rate of flowering. These associations might translate into selection for reduced height in years when the risk of grazing is high or when the water availability decreases too fast to allow all flowers to produce seeds. Hence, there is some congruence between past and current selection pressures when the phenotypic range is expanded and when performance variables other than head number are considered.