1 A trade-off between current and future reproduction, often referred to as
the cost of reproduction, is a fundamental assumption in life history theo
ry. In long-lived plants, large absolute differences in size between indivi
duals, storage of resources between reproductive events and organ preformat
ion may make such costs difficult to demonstrate, especially when only natu
ral variation is considered.
2 The long-lived legume Lathyrus vernus shows large size differences compar
ed with variation in carbon resource allocation, and is known to store reso
urces in below-ground rhizomes. We therefore followed individual plants ove
r a period of 4 consecutive years. We examined the cost of reproductive inv
estment by comparing the performance of untreated plants that differed in s
ize and herbivore damage. We also compared controls with plants where we ex
perimentally reduced flowering in terms of fitness measured as: survival, g
rowth, flower number, fruit:flower ratio and storage.
3 Natural patterns of flowering and fruiting provided no evidence of a nega
tive relationship between current and future reproduction. Individuals that
produced fruits did not experience a fewer probability of surviving and pr
oducing fruits the following season compared with flowering individuals tha
t failed to produce any fruits, even when differences in above-ground size
and herbivore damage were taken into account.
4 Flower removal in a single season increased the allocation to the rhizome
but the size of shoot buds for the next season was not increased. Experime
ntal manipulation of reproductive effort by repeated removal of flowers dur
ing 3 consecutive years, however, resulted in a significant increase in veg
etative size and the probability of flowering and setting fruit compared wi
th control plants.
5 While long-term data on natural variation in fruit production and short-t
erm experimental data provided no evidence of a cost of reproduction, such
a cost is still present, although detectable only after repeated flower rem