Phenotypic and Genotypic Components of Growth and Reproduction in Typha Latifolia: Experimental Studies in Marshes of Differing Successional Maturity

The objective of this study was to separate the genotypic and phenotypic variation in biomass allocation for populations of Typha latifolia from habitats of differing successional maturity. Field studies revealed that the OPEN marsh population of T. latifolia suffered high levels of ramet mortality over winter and had rapid growth in ramet numbers during the growing season. In contrast, the WOODS marsh population suffered predominantly from growing—season mortality with little ramet death over winter. The CATTAIL marsh population was intermediate in mortality patterns to the other two populations. Tissue nutrient analyses and fertilization experiments revealed that T. latifolia in the OPEN marsh was principally nutrient limited while T. latifolia in the WOODS marsh was light limited. The CATTAIL marsh population was exposed to conditions of nutrients and light intermediate to the other populations. Field studies of ¹ ⁴C fixation and allocation showed that both sexual and vegetative reproduction consisted of greater percentages of biomass production in the OPEN marsh population than in the CATTAIL or WOODS marsh populations. Ramets in the CATTAIL and WOODS marsh populations allocated a greater percentage of their fixed carbon to growth of the parent ramet. Allocation to roots was greatest in the OPEN marsh population and experiments showed this response to result from low nutrient availability. Leaf biomass was a fixed percentage of the total biomass under all conditions but the leaf volume:leaf mass ratio was greatest in the WOODS marsh population. Experiments revealed that the differences in leaf volume:mass were principally the result of light availability, but that decreased wind exposure also contributed to the high leaf volume:mass ratio. Difference in biomass allocation under uniform garden conditions indicated biotypic differences among populations such that habitats exposed to high levels of disturbance contained biotypes with high allocation to sexual reproduction. In contrast, the biotype from the habitat with the most intense level of density stress (WOODS—CATTAIL marsh biotype) allocated more biomass to root production, a trait potentially important for competition. Transplantation of biotypes into natural habitats showed that under nutrient—limiting conditions the WOODS—CATTAIL marsh biotype was more productive than the OPEN marsh biotype. This difference resulted from differences in allocation patterns whereby the OPEN biotype allocated a greater percentage of biomass to rhizome storage for sexual reproduction and the WOODS—CATTAIL biotype allocated more to root growth. Under light—limiting conditions no differences in productivity between biotypes occurred. It is concluded that both genotypic and phenotypic variation in biomass allocation contribute to the growth and reproduction of T. latifolia over a broad range of habitats differing in successional maturity. _kw biotypes.