Clonal integration increases performance of ramets of the fern Diplopterygium glaucum in an evergreen forest in southeastern China

Physiological integration is a major ecological advantage of clonal growth in angiosperms. Clonal growth is also common in pteridophytes, but almost no study has tested whether clonal integration increases performance in ramets of pteridophytes in natural populations. To test this hypothesis and also whether the positive effect of integration is greater on smaller ramets, we severed the connecting rhizomes of individual ramets of the common, understory fern Diplopterygium glaucum in an evergreen, broadleaf forest in southeastern China. In another experiment, we severed rhizomes around the edges of small plots each containing several ramets. After 19.5 weeks, survival was 100% in intact individual ramets but only 27% in severed ones. Among surviving ramets, final dry mass and lamina mass were also less in severed than in intact ramets, though stalk, rhizome, and root mass and maximum quantum yield of PSII (F_v/F_m) were not reduced. Individual ramets with fewer stalk nodes had lower dry mass but were not more affected by severing than ramets with more stalk nodes. Severance around the edge of plots did not significantly affect the combined final mass of the ramets within a plot. We conclude that clonal integration can have significant positive effects on both survival and growth of individual ramets of ferns in natural populations.