Fitness components and the determinants of fecundity in populations of a native perennial grass (Tridens flavus)

Abstract

AbstractUnderstanding intraspecific variation in traits that determine fitness is foundational to a trait‐based approach to plant ecology. This study examined fitness components during 3 years of reproduction in a polycarpic perennial bunchgrass (Tridens flavus) native to eastern North America that could prove useful in revegetating disturbed habitats. Plants were cultured from seeds of five populations in central New Jersey, USA, and planted in July 2015 into two undisturbed gardens 30 m apart that differed in availability of sunlight and soil moisture. Following flowering in 2016, 2017 and 2018, the number of panicles, seed set, seed number (fecundity) and seed mass were recorded. Final dry aboveground mass was determined. Seed set was high (>70%) in all populations and gardens. Panicle production varied with population and was strongly correlated with fecundity, but populations were not differentiated for other fitness components. Panicle and seed number were greatest in the drier garden with greater daily light availability. Mass per seed was reduced as more seeds were produced in the second and third year but showed low variation compared to fecundity. Vegetative mass was the most important variable determining fecundity. Close proximity of sampled sites and an outcrossed, wind‐pollinated mating strategy may have precluded detection of differentiation among T. flavus populations in the common gardens. High seed set, prodigious seed production on multiple panicles and high seed germinability and overwinter survival account for the occurrence of large populations of this native grass along roadsides and within successional fields and young woodlands throughout the region.