Patterns of biomass allocation to male and female functions in plants with different mating systems

Abstract

Using dry weight biomass we examined the patterns of investment in male and female functions (prezygotic cost) in plants with different mating systems. All the flower parts of both xenogamous and facultatively xenogamous species were heavier, i.e., larger, than those of facultatively autogamous species. Likewise, the dry weights of all the flower parts of xenogamous species exceeded those of facultatively xenogamous species. On a relative basis, xenogamous species invested less in calyces and more in corollas compared to species with the other mating systems. Facultatively autogamous species invested relatively more in pistils. Xenogamous species invested relatively more in stamens than do facultatively autogamous species. The ratios of dry weight stamens to dry weight pistils were equivalent in xenogamous and facultatively xenogamous species.The available data from xenogamous species suggest a pattern of resource allocation that is independent of sexual system (perfect-flowered, monoecious, or dioecious) and pollen vector. The cost of mating (prezygotic cost) was male biased and frequently exceeded by parental investment (postzygotic cost). These results are not consistent with models that predict equal allocation of resources to male and female sexual function but are consistent with those that predict unequal allocation of resources to those functions in outbreeding hermaphroditic angiosperms. Two additional lines of evidence are inconsistent with the expectations of sex allocation theory. First, resource allocation to sexual function was not equal in wind-pollinated species. Second, relative amounts of the resources allocated to male vis-à-vis female function did not decrease between xenogamy and facultative xenogamy i.e., with an increase in the selfing rate.

Theories of the Evolution of Dioecy

“…Lloyd (1984) discusses several extensions of this basic type of model, but the same general conclusion holds. This conclusion is in agreement with a large amount of data showing that measures of relative allocation to male functions, such as pollen/ovule ratios, show a negative relationship with levels of inbreeding (Schoen 1982;Cruden and Lyon 1985).…”

Floral Longevity: Fitness Consequences and Resource Costs

“…The total cost of constructing a flower includes the amount of carbon in the flower tissue (e.g., cellulose), as well as the metabolic energy expended during flower synthesis (Chapin, 1989). Estimates of the chemical composition of flowers and carbon cost per chemical constituent were used to calculate the construction cost for each species (Lovett-Doust and Harper, 1980;Cruden and Lyon, 1985;Chapin, 1989;Ashman and Baker, 1992). Flower construction costs range from 1.06 mg of carbon per flower of wild radish (Raphanus sativus) to 244.01 mg for trumpet creeper (Campsis radicans, Table 5.2).…”

The reproductive assurance benefit of selfing: importance of flower size and population size

“…Flower size can aVect not only a plant's attractiveness to pollinators (Thompson 2001;Elle and Carney 2003;Kennedy et al 2006) but its ability to self autonomously (Elle 2004), as smaller Xowers often have reduced anther-stigma separation (Eckhart and Geber 1999;Armbruster et al 2002). Smaller Xowers may evolve in response to selection for autonomous selWng ability in the absence of pollinators, either because of direct selection or under selection for resource savings once plants have become largely self-pollinating (Cruden and Lyon 1985). Small Xowers may also evolve due to other selective factors, i.e.…”