Water availability alters the relative performance of Salix sericea, Salixeriocephala, and their F-1 hybrids

Seedlings of Salix eriocephala Michx., Salix sericea Marsh., and their F-1 hybrids were tested for their growth under contrasting water conditions. On e-year old seedlings were grown in pots and subjected to one of two experim ents, a scheduled-watering experiment (watered every 1, 4, 8, or 12 days) o r a dry-down experiment (no watering after an initial period without water Limitation). In the scheduled-watering experiment, short-term growth of hyb rids was suppressed relative to the parents. However, subsequent watering a llowed hybrids to recover. By the end of the 48-day experiments, hybrids ex hibited heterosis across all treatments. In the dry-down experiment, hybrid s again were highly susceptible to the onset of drought conditions. From th ese results, we hypothesize that temporal and spatial variability in water availability could determine the survivorship of hybrids and the frequency of introgression; high water availability may enhance the relative performa nce of hybrids, while low water availability may limit hybrids.