Comparative response of closely related species to reduced competition. I.Senecio sylvaticusandS. viscosus

摘要

A comparison of the reproductive and vegetative responses ofSenecio sylvaticusandSenecio viscosusto the time and intensity of reduced competition is reported. The two species reacted similarly to thinning in terms of (1) reduced seed production per experimental population and increased seed production per individual, (2) reduced head production, (3) reduced vegetative dry weight, and (4) increased plant height.The two species ofSeneciodiffered in their reaction to thinning in terms of (1) initial anthesis, (2) number of seeds per head, and (3) mortality. Thinning had no significant effect in altering the initial flowering ofS. sylvaticus. Early thinning inS. viscosusadvanced the flowering date while late thinning delayed flowering.S. sylvaticuswas capable of increasing the number of seeds per head only if thinning occurred early, whereas the number of seeds per head inS. viscosussignificantly increased at all thinning periods. Lastly,S. sylvaticusexperienced much heavier mortality thanS. viscosus.