Salinity is increasing in wetland ecosystems, but the consequences for ecological communities are poorly understood. Iris hexagona is the only North American iris that survives in brackish marsh. Environmental salinity affects the physiology, growth, and reproduction of this glycophytic perennial, as well as plant-herbivore interactions. In brackish wetlands, 80% of iris flowers are consumed by white-tailed deer (Odocoileus virginianus), which rarely browse flowers in freshwater habitats. We investigated the effects of florivory and salinity on I. hexagona sexual and clonal reproduction. Irises that were protected from deer produced 20 times more mature seed capsules than unprotected plants. Experimental floral browsing increased both belowground clonal growth by 30% (P = 0.0003) and flower production the following year by 16% (P = 0.112). Iris populations differed significantly in clonal reproduction (P = 0.004), and interactions between salinity and population affected clonal (P = 0.005) and sexual (P = 0.054) output, suggesting that populations may be differentially adapted to environmental salinity. Brackish conditions can promote floral browsing and loss of sexual reproduction, but plants such as I. hexagona can compensate by allocating more resources to belowground clonal growth.
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Wetlands
Vol. 26 • No. 3
September 2006
Vol. 26 • No. 3
September 2006