K. Lehtila et Sy. Strauss, Effects of foliar herbivory on male and female reproductive traits of wildradish, Raphanus raphanistrum, ECOLOGY, 80(1), 1999, pp. 116-124
In this study, we examined how foliar herbivory affected the relative alloc
ation to male and female reproductive traits in a hermaphroditic plant. In
two experiments, one in the greenhouse and the other in a growth chamber, l
eaves of full sibling plants of the annual wild radish, Raphanus raphanistr
um, received one of four damage treatments to leaves (0, 25% [two types], o
r 50% leaf area removal). We controlled natural damage by Pieris rapae larv
ae through the use of clip cages. Measurements of both male and female repr
oductive characters were made on a series of flowers produced by each plant
over its lifetime. We measured pollen production, pollen size, ovule numbe
r, ovule size, petal size, nectar production, and sugar content. Effects of
herbivory on plant phenology were also assessed. At the end of the experim
ent, we quantified total flower production, fruit production, number of see
ds and fruit, and seed and vegetative biomass.
In general, male reproductive characters were more affected than female cha
racters by herbivory. Leaf herbivory reduced pollen number and pollen size,
whereas ovule size and number were not affected. Petal size, which we also
classify mon as a male trait, decreased with herbivory. Plants were genera
lly able to completely compensate for herbivory in the total number of flow
ers and fruit they produced; however, fewer fruits were found in the heavie
st damage treatment in the growth chamber experiment. We discuss alternativ
e explanations for this pattern based on developmental constraints and adap
tive responses. In summary, male fitness traits were much more strongly aff
ected by herbivory than were female traits; full compensation in seed produ
ction after herbivory may come at the cost of male reproductive success in
these hermaphroditic plants.