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Journal Article

Floral Sex Ratios and Life History in Aralia nudicaulis (Araliaceae)

Spencer C. H. Barrett and Kaius Helenurm
Evolution
Vol. 35, No. 4 (Jul., 1981), pp. 752-762
DOI: 10.2307/2408245
Stable URL: http://www.jstor.org/stable/2408245
Page Count: 11
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Floral Sex Ratios and Life History in Aralia nudicaulis (Araliaceae)
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Abstract

Aralia nudicaulis (Araliaceae) is a rhizomatous perennial which forms extensive clones and possesses a dioecious breeding system. In central New Brunswick, surveys of flowering ramets along roadsides revealed a 1:1 sex ratio. In forest sites however, a male-biased sex ratio occurs. Flowering female ramets of A. nudicaulis differ from males in a range of secondary sex characters. These include: significantly fewer flowers per inflorescence, earlier average flowering, greater total biomass, greater vegetative biomass, and higher relative growth rate during flowering. Reproductive effort in male ramets is significantly higher than in females at peak flowering. Subsequently, male inflorescences wither while female reproductive effort increases to a maximum during fruit maturation. Thus, for a 6-wk period, female ramets incur a cost not experienced by males. The timing and rate of senescence of male and female ramets are similar. A lower density of flowering female ramets in forest sites suggests that the flowering capacity of females is reduced under low light regimes in comparison with males. This is probably due to the greater resource expenditure associated with fruit production in females.

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