Evol Ecol Res 6: 813-832 (2004)     Full PDF if your library subscribes.

The effects of maternal salinity and seed environment on germination and growth in Iris hexagona

Peter A. Van Zandt* and Susan Mopper

Department of Biology, University of Louisiana at Lafayette, Lafayette, LA 70506-2451, USA

Address all correspondence to Peter A. Van Zandt, Department of Biology, Washington University, 1 Brookings, Campus Box 1137, St. Louis, MO 63130, USA.
e-mail: vanzandt@biology2.wustl.edu


Seed germination and seedling establishment are determined by local environmental conditions as well as by the environment of the parental generation, resulting in a type of trans-generational phenotypic plasticity known as an inherited environmental effect. Parental effects should be adaptive in habitats where the selective environment is spatially and temporally predictable, and where parental effects confer a fitness advantage. Natural populations of the native wetland perennial Iris hexagona occupy saline habitats and plant performance is strongly impacted by salinity stress. We examined the capacity for environmental effects to act directly and indirectly on the germination responses of I. hexagona by (1) growing plants in three different maternal salinity levels in a common garden, (2) performing crosses through hand pollinations, and (3) planting the resulting seeds in four different salinity environments in a greenhouse study. Our results indicate that salinity has strong direct and indirect effects on seed germination. Direct exposure to salinity delayed and reduced seed germination and produced seedlings with 32% less mass than those grown in the freshwater treatment. Seeds produced by maternal plants growing in high salinity germinated earlier and in greater numbers than seeds from low salinity plants, demonstrating an indirect effect of the maternal environment. Maternal effects were no longer detectable 10 days after germination, indicating that the indirect effect of salinity was more influential on germination timing and success than on seedling growth. Furthermore, the maternal effect was only apparent in saline environments, suggesting that salinity-induced maternal effects are context dependent. These maternal effects may confer an advantage and be adaptive for I. hexagona in salt marsh populations.

Keywords: adaptive maternal effects, Louisiana, Marsh Island, saline marsh, salinity stress, survival analysis.

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