Developmentally Programmed Division of Labor in the Aquatic Invader Alternanthera philoxeroides Under Homogeneous Soil Nutrients

Abstract

Clonal traits can contribute to plant invasiveness, but little is known about the roles of division of labor (a key clonal trait) in homogeneous habitats. The hypothesis tested is that clonal integration allows division of labor and increases the overall performance of an invasive clonal plant, especially under higher soil nutrients. Clonal fragment pairs of aquatic invader Alternanthera philoxeroides (each with four ramets and a stolon apex) were grown in two homogenous habitats with high or low soil nutrient supply, and with stolon connections being either severed (clonal integration prevented) or kept intact (clonal integration allowed). Results showed that stolon connection allowed the division of labor within the clonal fragment, with basal ramets specializing in acquisition of belowground resources and apical ramets specializing in acquisition of aboveground expansion. Moreover, the capacity for division of labor was greater, which brought the clonal fragments of A. philoxeroides stronger clonal propagation and better performance in high nutrient habitats than in low nutrient habitats. The results supported our hypotheses that the developmentally programmed division of labor may facilitate the clonal expansion of this aggressive invader in some homogeneous habitats with high resource availability.

Sharing of nitrogen between connected ramets of Alternanthera philoxeroides in homogeneous environments

“…And then, the apical part appeared to import less 15 N that was assimilated by the basal part. The phenomenon was especially obvious in the accumulation of 15 N in leaves and stems of apical parts, implying that an increase in external N level might, to some degree, weaken the source-sink relationship between younger and older ramets; thus, higher external N levels may alleviate the demand for N supply via stolon connections by young A. philoxeroides ramets (Dong et al 2015;Xi et al 2019).…”

“…Clonal integration is a distinguishing life-history trait of clonal species that allows for the transport and sharing of internal resources (e.g., carbohydrates, water, and mineral nutrients) among connected ramets within the same clone (Alpert and Mooney 1986; de Kroon and van Groenendael 1997;Song et al 2013; Wang et al 2021). Numerous studies have demonstrated that such physiological integration can improve the performance of clones in heterogeneous environments, where connected ramets experience different levels of external resources such as light, water, or nitrogen (Alpert 1996; de Xi et al 2019). This is partly because the performance of clonal fragments in homogeneous environments has often been treated as an experimental control for effects of integration, with the assumption that clonal integration tends to impose no effect when resource availability is spatially uniform (Song et al 2013; Wang et al 2021).…”

“…This is partly because the performance of clonal fragments in homogeneous environments has often been treated as an experimental control for effects of integration, with the assumption that clonal integration tends to impose no effect when resource availability is spatially uniform (Song et al 2013; Wang et al 2021). However, an increasing body of studies have suggested that, even in homogeneous environments, variation in the developmental age of individual ramets could cause differences in the ability of ramets to obtain external resources, in addition to any internal gradient in resource availability (Alpert 1996;Roiloa et al 2013;Dong et al 2015;Xi et al 2019). Such physiological differences may thus trigger the movement of internal resources among ramets and in uence the tness of clones in homogeneous environments.…”

“…Therefore, a plausible prediction is that an increase in external resource availability may strengthen the donor role of older ramets in sharing resources between ramets; this may thereby increase the transfer rate of N, particularly when the direction of N transport was already toward younger ramets. Correspondingly, the net effect of integration on clonal performance should be more positive at higher levels of external resource supply (Dong et al 2015;Xi et al 2019).…”

Warming and elevated nitrogen deposition accelerate the invasion process of Solidago canadensis L.

“…Based on the above-described treatment conditions, the plants were destructively harvested after 83 days of exposure to warming and N deposition. Leaf nitrogen content and chlorophyll were measured using a portable chlorophyll meter (TYS-A, TOP, Zhejiang, China) before the final harvest (Xi et al 2019). Leaf shape index (LSI) was calculated as the ratio of leaf length to the corresponding leaf width (Wang et al 2016).…”