Differential Influence of Clonal Integration on Morphological and Growth Responses to Light in Two Invasive Herbs

Background and aims: In contrast to seeds, high sensitivity of vegetative fragments to unfavourable environments may limit the expansion of clonal invasive plants. However, clonal integration promotes the establishment of propagules in less suitable habitats and may facilitate the expansion of clonal invaders into intact native communities. Here, we examine the influence of clonal integration on the morphology and growth of ramets in two invasive plants, Alternanthera philoxeroides and Phyla canescens, under varying light conditions. Methods: In a greenhouse experiment, branches, connected ramets and severed ramets of the same mother plant were exposed under full sun and 85 % shade and their morphological and growth responses were assessed. Key results: The influence of clonal integration on the light reaction norm (connection6light interaction) of daughter ramets was species-specific. For A. philoxeroides, clonal integration evened out the light response (total biomass, leaf mass per area, and stem number, diameter and length) displayed in severed ramets, but these connection6light interactions were largely absent for P. canescens. Nevertheless, for both species, clonal integration overwhelmed light effect in promoting the growth of juvenile ramets during early development. Also, vertical growth, as an apparent shade acclimation response, was more prevalent in severed ramets than in connected ramets. Finally, unrooted branches displayed smaller organ size and slower growth than connected ramets, but the pattern of light reaction was similar, suggesting mothe

Heterogeneous Light Supply Affects Growth and Biomass Allocation of the Understory Fern Diplopterygium glaucum at High Patch Contrast

Spatial heterogeneity in resource supply is common and responses to heterogeneous resource supply have been extensively documented in clonal angiosperms but not in pteridophytes. To test the hypotheses that clonal integration can modify responses of pteridophytes to heterogeneous resource supply and the integration effect is larger at higher patch contrast, we conducted a field experiment with three homogeneous and two heterogeneous light treatments on the rhizomatous, understory fern Diplopterygium glaucum in an evergreen broad-leaved forest in East China. In homogeneous treatments, all D. glaucum ramets in 1.5 m×1.5 m units were subjected to 10, 40 and 100% natural light, respectively. In the heterogeneous treatment of low patch contrast, ramets in the central 0.5 m×0.5 m plots of the units were subjected to 40% natural light and their interconnected ramets in the surrounding area of the units to 100%; in the heterogeneous treatment of high patch contrast, ramets in the central plots were subjected to 10% natural light and those in the surrounding area to 100%. In the homogeneous treatments, biomass and number of living ramets in the central plots decreased and number of dead ramets increased with decreasing light supply. At low contrast heterogeneous light supply did not affect performance or biomass allocation of D. glaucum in the central plots, but at high contrast it increased lamina biomass and number of living ramets older than annual and modified biomass allocation to lamina and rhizome. Thus, clonal integration can affect responses of understory ferns to heterogeneous light supply and ramets in low light patches can be supported by those in high light. The results also suggest that effects of clonal integration depend on the degree of patch contrast and a significant integration effect may be found only under a relatively high patch contrast

The effect of stolon fragmentation on the colonization of clonal invasive Carpobrotus edulis in a coastal dune system: A field test

Disturbances usually initiate processes of fragmentation in clonal plants, with the consequent division into portions of different size. The ability of these portions to survive and regrow after fragmentation plays an important role in the maintenance of populations and the colonization of new environments. In this field experiment we aim to determine the importance of stolons as reserve organs in the colonization of a coastal sand dune by a clonal invader. We simulated an event of fragmentation of clones of an aggressive invader into portions with short and long stolon sizes. Our results showed a reduction of biomass allocation to roots in the long stolon treatment that was balanced by an increase in the above-ground growth; consequently, the area colonized by the invader was greater. We report evidence that stolons can contribute to buffering stressful conditions and allow expansion of the invader into a natural coastal sand dune. © 2016 The Society for the Study of Species Biology.Associated Grant:Financial support for this study was provided by the Spanish Ministry of Economy and Competitiveness (project Ref. CGL2013-44519-R, awarded to SRR). This project was co-financed by the European Regional Development Fund (ERDF)

The effect of stolon fragmentation on the colonization of clonal invasive Carpobrotus edulis in a coastal dune system: A field test

Disturbances usually initiate processes of fragmentation in clonal plants, with the consequent division into portions of different size. The ability of these portions to survive and regrow after fragmentation plays an important role in the maintenance of populations and the colonization of new environments. In this field experiment we aim to determine the importance of stolons as reserve organs in the colonization of a coastal sand dune by a clonal invader. We simulated an event of fragmentation of clones of an aggressive invader into portions with short and long stolon sizes. Our results showed a reduction of biomass allocation to roots in the long stolon treatment that was balanced by an increase in the above-ground growth; consequently, the area colonized by the invader was greater. We report evidence that stolons can contribute to buffering stressful conditions and allow expansion of the invader into a natural coastal sand dune. © 2016 The Society for the Study of Species Biology