Costs and benefits of vegetative propagation in the desert tulip

The effects of vegetative propagation on plant performance in the desert tulip Tulipa systola were studied experimentally. A differentiation was made between immediate effects (possible tradeoffs between vegetative propagation and seed production) and ultimate costs or benefits (reduction in overall plant growth and biomass production efficiency per unit leaf mass, and within-clone competition). The results of a garden experiment with either single bulbs (single-ramet genets) and clusters of bulbs (multi-ramet genets) of the same total size, exposed to three levels of irrigation, did not show immediate nor ultimate disadvantages of vegetative propagation in terms of seed production or plant growth parameters. Competition between ramets of the same genet seemed to occur at low soil moisture availability, but it did not cause a disadvantage to multi-ramet genets relative to single-ramet genets. Vegetative propagation as a safeguard against complete genet consumption by porcupines is also discussed. Finally, the hypothesis is proposed that, in stead of influencing sexual reproduction negatively, vegetative propagation may in fact increase lifetime seed production, because multi-ramet genets may produce more fruits than single-ramet genets having the same level of genet growth.