Tuesday, August 7, 2007

PS 21-4: Why woolly bears like hermaphrodite flowers: Corolla size affects florivore choice

Andrew C. McCall, Denison University

More research is being conducted intothe effects of floral damage on plant fitness as well as plant defenses that can combat this damage.  Much less is known about what motivates florivores to choose what flowers to eat.  Here I show that woolly bears, Platyprepia virginalis (Arctiidae), common florivores on Nemophila menziesii (Boraginaceae, sensu stricto), prefer to eat hermaphrodite flowers over females.  This pattern has been observed for over three field seasons in coastal California populations.  In the lab, both initial preference to feed and the proportion of damage per flower in choice and non-choice tests is higher on hermaphrodites than on females.  An artificial reduction of size in hermaphrodites is sufficient to eliminate this preference for hermaphrodite flowers.  In contrast, anther removal in hermaphrodites was not sufficient to eliminate the preference, so it appears that P. virginalis may choose hermaphrodites on the basis of corolla size but not on the basis of male reproductive structures.  More research into florivore preference for hermaphrodite flowers in other taxa may identify little-studied selection pressures that shape floral traits like corolla size.