The effects of leaf litter and competition from hybrid cattails (Typha×glauca) on the seed germination and seedling performance of its parental species

• Published in: Aquatic botany 2018-02, Vol.145, p.29-36
• Main Authors: Szabo, Jessica, Freeland, Joanna R., Dorken, Marcel E.
• Format: Article
• Language: English
• Subjects: Aquatic plants; Biological competition; Common-garden experiment; Competition; Freshwater plants; Genetic diversity; Genetic variation; Germination; Indigenous species; Interactions; Introduced species; Invasive plants; Invasive species; Leachates; Leaf litter; Leaves; Natural populations; Pollination; Population genetics; Seed germination; Seedlings; Seeds; Shading; Typha; Typha latifolia; Typha × glauca
• ISSN: 0304-3770; 1879-1522
• DOI: 10.1016/j.aquabot.2017.11.009

•Hybrid cattails (Typha×glauca) increasingly threaten native cattails (T. latifolia).•We show that leachate from hybrid leaf litter reduces germination of parent but not hybrid seeds.•We found no evidence that leachate affects cattail seedling growth.•Recurrent seed germination is an important feature of cattail populations.•We therefore identified an additional facilitator of hybrid cattail wetland dominance. Invasive species affect native vegetation through combinations of direct interactions (e.g. competition) and indirect interactions (e.g. altered pollination regimes) mediated through the occupation of shared environments. Hybrid cattails (Typha×glauca) are rapidly displacing their parental species, the native broadleaf cattail (T.latifolia) and the introduced narrow-leaf cattail (T. angustifolia), but the mechanisms involved are poorly understood. We evaluated the potential for direct and indirect interactions among cattails using a series of experiments. First, we evaluated whether seed germination was affected by hybrid leaf litter using a factorial experiment in which we tested for indirect effects of leaf-litter leachate and shading. Second we tested whether these indirect effects of hybrid leaf litter affected seedling performance using a factorial common-garden experiment. Finally, we tested for direct competitive interactions between hybrid and native cattail seedlings. One or more components of hybrid leaf-litter leachate strongly reduced the germination of the parental cattail species, but not that of the hybrid. There was no evidence that direct competitive interactions affected seedling performance. Because regular recruitment by seeds appears to be important in shaping patterns of genetic diversity in natural populations, our findings provide a mechanism for explaining the dominance of hybrid cattails in eastern North America.