Demography and pollination ecology of Trillium grandiflorum in hedgerow corridors and forest patches

Hedgerows are assumed to provide suitable habitats and dispersal corridors in agricultural landscapes for forest herbs, but these functions have rarely been tested. Assuming that hedgerows can sustain viable populations solely from vegetation survey can be misleading since it does not take into account extinction lag and demographic processes. I address the question of hedgerow's suitability for forest herbs by comparing the demography and pollination biology of Trillium grandiflorum in hedgerow corridors and forest patches of an agricultural landscape. Specifically I ask: Do population structure and individual performance of T. grandiflorum differ between hedgerows and forests? Are pollination services comparable in hedgerows and forests? How do variations in growth, survival, and reproduction influence demography in hedgerows and forests?;Populations in hedgerows were characterized by lower proportion of seedling and juvenile per mature plant, but also by better flower and ovule production than in forests. Pollen limitation was comparable between habitats, suggesting that pollination services in hedgerow's are at least as good as in forests. Pollination varied at the landscape scale and over time, and declined with spatial isolation in hedgerows. Lower survivorship of early growth stages negatively affected population growth rate in hedgerows, but this effect was partly counterbalanced by better growth and shorter maturation time than in forests. Stochastic growth rates indicate that populations in hedgerows are more prone to extinction than populations in forests.;These findings show that presence of long-lived species in hedgerow habitats does not insure that these habitats will continue to support viable populations. T. grandiflorum in hedgerows appears at higher risk of extinction than in forests but, when conditions are right, populations may persist long enough to effect dispersal between habitat patches and provide resources for pollinators in agricultural landscapes.;Individual plant performance and population structure was determined from field observations and experiments conducted in a system of hedgerows connected to forests. I conducted pollination and transplantation experiments to test for variation in pollination and reproduction among habitats and with increasing isolation. Populations monitored for three years in hedgerows and forests were used to construct transition matrix models and to compare their dynamics.