Ecological and Genetic Comparison between Ray and Disc Achene Pools of the Heteromorphic Species Prionopsis ciliata (Asteraceae)

Dimorphic ray and disc achenes of Prionopsis ciliata (Asteraceae) were compared to determine whether ecological and genetic differences exist that correspond to structural differences between achene morphs. Ray achenes were significantly heavier and took a significantly longer time to germinate than disc achenes, which is indicative of differing dispersal and demographic functions between achene morphs. Significant heterozygote deficiency was detected in ray and disc achene seed pools. Mean observed heterozygosity across all populations and within two populations was significantly greater in the disc achene pool than in the ray achene pool. FIT and FIS were significantly higher and GST was significantly lower in the ray achene pool than the disc achene pool. Overall, ray and disc florets were predominantly self-fertilized. Significant differences in outcrossing rates were detected between ray and disc florets within five populations. The results do not indicate a clear relationship between ecological function of an achene morph and genotype of the seed contained within a morph. Subtle genetic differences between ray and disc achene pools, however, could influence metapopulation genetic dynamics and shape patterns of genetic architecture on the landscape.