PARENT SESSION
Oral Session #5: Plant Demography and Reproductive Ecology.
Presiding: R. Kobe
Monday, August 5. 8:00 AM to 11:30 AM. Coconino Meeting Room, TCC.

Variation in sexual and asexual reproduction in the understory herb, Arisaema triphyllum: persistence and physiological constraints.

Levine, Mia^*,1, Feller, Ilka², ¹ Smithsonian Environmental Research Center, Edgewater, Maryland² Smithsonian Environmental Research Center, Edgewater, Maryland

ABSTRACT- Long-lived understory herbs experience a highly dynamic forest over space and time, yet can persist for more than a century. To understand these persistence patterns, I examined the effect of forest age and disturbance on potential sexual and asexual reproduction in the sex-changing perennial, Arisaema triphyllum. Populations in 100-year-old forest understory are highly male-skewed (1:40, F:M) relative to populations both in light gaps of the same forests(1:2), and in the 50-year-old forest understory (1:3). In contrast, asexual reproduction (# of cormlets/individual) does not differ significantly among the three forest states. Of seven environmental variables measured, only light and plant density contributed significantly to the variation in sex ratio, while no measured variables explained the variation in number of asexual offspring. A significantly higher cost of sexual reproduction (flower+stalk biomass/total biomass) for males in the undisturbed, 100-year-old forest may explain the absence of females, while the invariant cost of asexual reproduction (cormlet biomass/total biomass) may explain the similarity in average number of cormlets per individual per season across forest states. Increasing the availability of stored resources (via bud removal) also does not affect the cost, number, or size of asexual offspring. These results suggest that sexual reproduction is resource-limited, while asexual reproduction is resource-independent. My findings are discussed in light of physiological constraints and persistence strategies potentially employed by this and other herbs reproducing both sexually and asexually.

KEY WORDS: Arisaema triphyllum, sex ratio, cost of reproduction, forest succession