Trade-offs between clonal and sexual reproduction in Sagittaria latifolia (Alismataceae) scale up to affect the fitness of entire clones

Many plants combine sexual reproduction with vegetative propagation, but how trade-offs between these reproductive modes affect fitness is poorly understood. Although such trade-offs have been demonstrated at the level of individual shoots (ramets), there is little evidence that they scale up to affect genet fitness. For hermaphrodites, reproductive investment is further divided between female and male sexual functions. Female function should generally incur greater carbon costs than male function, which might involve greater nitrogen (N) costs. Using a common garden experiment with diclinous, clonal Sagittaria latifolia we manipulated investment in reproduction through female and male sex functions of 412 plants from monoecious and dioecious populations. We detected a 1 : 1 trade-off between biomass investment in female function and clonal reproduction. For male function, there was no apparent trade-off between clonal and sexual reproduction in terms of biomass investment. Instead, male function incurred a substantially higher N cost. Our results indicate that: trade-offs between investment in clonal propagation and sexual reproduction occur at the genet level in S.similar to latifolia; and sexual reproduction interferes with clonal expansion, with investment in female function limiting the quantity of clonal propagules produced, and investment in male function limiting the nutrient content of clonal propagules.