Sprouting in woody plant species allows for the long-term persistence of small isolated populations experiencing changing environments and can preserve genetic diversity in these populations despite the infrequent recruitment of sexually produced individuals. We examined demographic data collected over a 10-year period for Tilia americana var. caroliniana in the context of genetic data as an empirical case study of this concept. Two back-barrier islands on the Georgia USA coast were completely censused for Tilia americana var. caroliniana. Recruitment, growth, and mortality of all stems were tracked over a 10-year period. All genets were genotyped using eight nuclear microsatellite loci to assess population genetic structure among sampled stems, as well as among populations in the region.
The two island populations exhibited differences in ability to establish seedlings despite them having similarities in flowering frequency. Seedling mortality was high throughout the 10-year period, and cycling of ramets within genets was common. Long-term recruitment in this system appears to be primarily a result of vegetative growth via basal sprouts. Genetic structure was limited, both between islands and among populations in the region. Long-lived woody species that persist by vegetative reproduction may unexpectedly influence regional forest responses to climate change, particularly on the lagging-edge of a species distribution.
Population Persistence in Coastal Basswood
Ashley Morris, Middle Tennessee State University
Evans, J.P., and A. Morris. 2016. Isolated coastal populations of Tilia americana var. caroliniana persist long-term through vegetative growth. American Journal of Botany 103:1687-1693.