Resource Allocation and Reproduction in Populations of Amphicarpum Purshii (Gramineae)

Abstract

Five New Jersey populations of Amphicarpum purshii (an annual panicoid grass) were investigated as to total allocation of biomass to reproduction and its distribution between aerial chasmogamous and subterranean cleistogamous inflorescences. Germination of both types of seed was documented, for the first time, in not only the field but under three laboratory temperature regimes. Overall, approximately 29 % of the shoot biomass was allocated to reproduction. On a population basis, subterranean inflorescences accounted for 37–100 % of the reproductive biomass, and these seed (5 × heavier but fewer in number) were the source of most surviving seedlings. Subterranean spikelets contained caryopses significantly more frequently than aerial spikelets. The ratio of the number of viable aerial seed to the number of viable subterranean seed increased from 0/4 to 4/2 with recentness and/or frequency of disturbance. As a pioneer species in secondary succession, Amphicarpum purshii produces a larger subterranean propagule, with greater seedling vigor and a higher probability of local reproductive success, and also a smaller aerial propagule in larger numbers with potentially greater genetic variability.

Analysis of Inbreeding Depression in Mixed-Mating Plants Provides Evidence for Selective Interference and Stable Mixed Mating

“…We also excluded estimates based on measures of the fitness of selfed and open-pollinated crosses, which can be biased by selfing in the open-pollinated crosses. Finally, we excluded comparisons of progeny from cleistogamous and chasmogamous flowers because these can be biased both by selfing in the chasmogamous flowers and by nongenetic differences in the sizes and germination behaviors of seeds produced by the two flower types (see, e.g., McNamara and Quinn 1977;Lu 2002). For each population, we recorded fitness components for up to four life-cycle stages.…”

Environmental and Genetic Determinants of Cleistogamy in a Natural Population of the Grass Danthonia spicata

“…Energetic costs of chasmogamous seeds are two to three times greater than for cleistogamous seeds in Impatiens pallida and I. bifiora (Schemske, 1978). Cleistogamous seedlings are more common than chasmogamous seedlings in populations of Amphicarpum purshii (McNamara and Quinn, 1977) even though seeds are produced in roughly equal numbers.…”

“…Small plants, plants lacking adequate water or light, or plants growing in dense stands may produce solely cleistogamous flowers while other plants, in better conditions, may produce predominantly chasmogamous flowers (Koller and Roth, 1964;Levin, 1972;Schemske, 1978;Waller, 1980;Weiss, 1980;Thompson and Beattie, 1981). It appears chasmogamous flower production is more plastic than cleistogamous flower production in Danthonia spicata as well, as evidenced by the lower heritability for the total number of chasmogamous flowers per plant, but Danthonia does not exhibit drastic fluctuations in the percentage of cleistogamous flowers so commonly reported in other species (Levin, 1972;McNamara and Quinn, 1977;Waller, 1980;Weiss, 1980). Cleistogamy in the grasses has been subdivided into four discrete types (Hackel, 1906); this classification was later extended to all flowering plants (Uphof, 1938).…”

Dispersal and Plant Mating Systems: The Evolution of Self-Fertilization in Subdivided Populations

“…For example, in several species of Viola (Violaceae) Culver and Beattie (1978) found that seeds from cleistogamous flowers were taken by ants less frequently than seeds from chasmogamous flowers, even though seeds from cleistogamous flowers had larger elaiosomes. There are also some plant species in which the cleistogamous flowers are subterranean and their diaspores are non-dispersive, e.g., Gymnarrhena micrantha (Asteraceae) (Koller and Roth, 1964) and Amphicarpum purshii (Poaceae) (Chase, 1918;McNamara and Quinn, 1977). Schmitt et al (1985) have also shown that seeds are dispersed farther from chasmogamous capsules ofthe explosively dehiscent Impatiens capensis (Balsaminaceae) than from the cleistogamous capsules.…”