Does light availability influence the trade-off between sexual and clonal reproduction?

Background/Question/Methods A large proportion of understory herbs reproduce by making seeds and clonal propagules (small plantlets).  Theory has predicted that a trade-off exists between allocation to each reproductive mode, although few field studies have quantified this trade-off.  It remains unclear what resources (i.e. carbon, mineral nutrients) are being traded-off.  It has been argued that limited carbon mediates this trade-off, and therefore light availability should influence the trade-off between sexual and clonal reproduction.  Using the understory herb Calathea marantifolia as a model system I tested this hypothesis using an experimental field approach. I manipulated the sexual output of plants, producing three treatment groups (high, medium and low reproductive effort) and quantified the Global Site factor of each individual using digital photographs.  The subsequently produced clonal plantlet on each adult was followed for one year, tacking its survival and growth bimonthly.

Results/Conclusions

Sexual reproductive effort treatments had a significant effect on the growth of clonal plantlets but Global Site factor was not a significant covariate in the analysis.  As expected clonal plantlets produced on plants with low reproductive effort were the largest.  However, contrary to expectations plants with medium sexual reproductive effort had the smallest clonal plantlets.  Clonal plantlet survival was not affected by sexual reproductive effort treatments.  These results suggest that carbon my not be responsible for the allocation trade-off between sexual and clonal reproduction.