The effect of apical meristem damage on the fitness of Cirsium pitcheri.

Abstract

Plants are known to exhibit a compensatory response to natural herbivory and other sources of damage. This study was intended to verify whether damage to the apical of meristem of Cirsium pitcheri resulted in overcompensation. We addressed the following questions: 1) Does pollinator activity differ between undamaged (single-stemmed) and damaged (multi-stemmed) C. pitcheri? 2) Is there a difference in fitness between single- and multi-stemmed individuals after apical meristem injury? To assess these questions we marked single- and multi-stemmed thistles at Sturgeon Bay, MI and surveyed various measures of fitness including, flowering and non-flowering heads, seed production, and pollinator activity. There was a significant difference in the number of total heads and seeds produced per plant between single- and multi-stemmed individuals. These results indicate that multi-stemmed C. pitcheri were exhibiting overcompensation after apical meristem damage, and thus increased their relative fitness relative to single-stemmed plants.