Differentiation between the Sexes of Rumex hastatulus in Net Energy Allocation, Flowering and Height

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Abstract
Patterns of enery allocation, inflorescence height and time of anthesis were studied in a greenhouse for the sexes of R. hastatulus, a dioecious annual colonizer. Four soil fertility levels and 4 densities were employed to determine whether shifts in sex ratio could be induced and whether males and females differed in their patterns of energy allocation. The sex ratio did not change in response to density and nutrient treatments and remained near 53% female:47% male. Males flowered significantly earlier than females and had shorter inflorescences. Females contained more total energy than males and contained more energy in roots, inflorescences and inflorescence leaves. Females allocated both a higher total amount of energy and a higher proportion of energy to reproduction than did males. Except for total energy and proportion of energy allocated to reproduction, energy allocation patterns for males and females were similar in response to the density and nutrient treatments. These results are discussed both in terms of niche partitioning between the sexes and in terms of differences in optimal reproductive strategies of males and females.