Dynamics Of Clonal Reproduction In Common Milkweed (Asclepias Syriaca)

Clonal reproduction is a common reproductive strategy in plants; however, the majority of population models ignore clonality entirely, limiting their usefulness for understanding both population dynamics and the evolution of clonal plants. To address this gap, we created an integral projection model (IPM) for common milkweed (Asclepias syriaca), a clonal plant species, that incorporates genetic identity. Demographic data were collected from all putative individuals (ramets) in 4 common milkweed populations in Northern Virginia from 2021 to 2023. All ramets were mapped, and up to 70% (n=1675) were genotyped at 7 microsatellite loci to identify unique clones (genets). First, we analyzed milkweed spatial-genetic structure and genotype-phenotype covariance. Then, we characterized clone size and demographic rates. Finally, we modeled ramet vital rate responses (flowering and pod production) with fixed (ramet height and herbivory) and random effect (genet identity and site) structures to construct the IPM. To quantify the impact of clonality on ramet population growth, we performed elasticity analysis. In these populations, clonal reproduction was ubiquitous (unique genotypes/individuals sampled = 0.10), and milkweed clones were large and spatially aggregated, conflicting with previous research. In the IPM, clonal parameters, especially budding probability and number of buds per stem, had the highest proportional effect on the population growth rate (elasticity = 1.5), and genetic identity explained variation in ramet sexual reproduction. This underscores the role of clonal reproduction in driving population dynamics, and further work is needed to investigate the processes behind patterns of clonal reproduction, as well as genet dynamics in clonal plants.