Effects of fragmentation on the survival and growth of the invasive, clonal plant Alternanthera philoxeroides

Abstract

The capacity of small clonal fragments to survive and grow is a major factor in the spread of clonal plants, especially aquatic species. This study of the introduced, invasive, amphibious, stoloniferous herb Alternanthera philoxeroides in China tested the effects of fragment size, of loss of the stolon apex, and of the original position of a fragment within a clone before fragmentation on the survival and growth of fragments in a greenhouse experiment. The stolon internodes of plants consisting of one stolon with 5 ramets were severed in all 16 possible patterns, generating fragments of 1-5 ramets. These 16 fragmentation treatments were crossed with removal of the stolon apex. Fragmentation and apex removal did not affect total growth of plants, but more highly fragmented plants produced smaller, more numerous ramets. The survival of fragments consisting of one original ramet was about 85%, compared to 100% survival of fragments with 5 original ramets. Fragments consisting of the youngest ramets along the original stolon grew more than fragments of the same size that consisted of older ramets. These effects of fragmentation on growth provide new evidence for clonal integration of the rate at which connected ramets produce new ramets and novel evidence that fragments produced from different portions of clones have different potential for spread. They further suggest that detachment of small groups of distal ramets along stolons in the field might be very effective in spreading the species and that a trade-off between the number and the size of new ramets produced by fragments may represent an adaptive, plastic response to disturbance. Results do not recommend intentional fragmentation of clones as a means of controlling the rate of growth of this invasive species but suggest that incidental fragmentation may not increase its growth in mass, although it may increase its rate of spread.

Clonal integration in homogeneous environments increases performance of Alternanthera philoxeroides

“…Severance can release more distal ramets from apical dominance by more proximal ramets in various species (Evans and Whitney 1992;Balestri and Lardicci 2013;Gao et al 2013). In A. philoxeroides, severance from proximal ramets can induce distal ramets to produce more offspring with no change in the total mass of clonal fragments (Dong et al 2012 recently found that interactive effects of severance and environment on growth in mass and on production of new ramets differed in the grass Phalaris arundinacea, and clonal reproduction and total accumulation of mass show different effects of nutrient availability in the aquatic clonal plant Eichhornia crassipes (You et al 2014). Measures of reproduction and spread may thus require different treatment than measures of mass in models of effects of clonal integration in homogeneous environments.…”

The invasive plant Alternanthera philoxeroides benefits from clonal integration in response to defoliation

“…This species is one of the world's worst invasive weeds and is listed as one of the 16 worst alien invasive weeds in China (Julien et al, 1995;Ma and Wang, 2005). A. philoxeroides often suffers natural disturbances, such as herbivory, mowing and trampling, which may fragment its clones into pieces Dong et al, 2010Dong et al, , 2012. In China, A. philoxeroides has extremely low genetic diversity (Xu et al, 2003;Wang et al, 2005), and clonal integration may play an important role in determining its growth and spread (Wang et al, , 2009Xu et al, 2010).…”

Does clonal resource translocation relate to invasiveness of Typha taxa? Results from a common garden experiment

“…Therefore clonal traits likely play an important role in community assembly and invasion; indeed several studies have demonstrated a link between clonality and invasion success (Otfinowski and Kenkel, 2008;Okada et al, 2009;Roiloa et al, 2010;Li and Wang, 2011;Dong et al, 2012). Though the importance of clonal traits is well-established, data on clonal traits in invasive plants are not as widely available as more commonly-measured leaf and seed characteristics (van Kleunen et al, 2010; but see Klimešová and de Bello, 2009).…”