High Tolerance to Salinity and Herbivory Stresses May Explain the Expansion of Ipomoea Cairica to Salt Marshes

Abstract

BackgroundInvasive plants are often confronted with heterogeneous environments and various stress factors during their secondary phase of invasion into more stressful habitats. A high tolerance to stress factors may allow exotics to successfully invade stressful environments. Ipomoea cairica, a vigorous invader in South China, has recently been expanding into salt marshes.Methodology/Principal FindingsTo examine why this liana species is able to invade a stressful saline environment, we utilized I. cairica and 3 non-invasive species for a greenhouse experiment. The plants were subjected to three levels of salinity (i.e., watered with 0, 4 and 8 g L−1 NaCl solutions) and simulated herbivory (0, 25 and 50% of the leaf area excised) treatments. The relative growth rate (RGR) of I. cairica was significantly higher than the RGR of non-invasive species under both stress treatments. The growth performance of I. cairica was not significantly affected by either stress factor, while that of the non-invasive species was significantly inhibited. The leaf condensed tannin content was generally lower in I. cairica than in the non-invasive I. triloba and Paederia foetida. Ipomoea cairica exhibited a relatively low resistance to herbivory, however, its tolerance to stress factors was significantly higher than either of the non-invasive species.Conclusions/SignificanceThis is the first study examining the expansion of I. cairica to salt marshes in its introduced range. Our results suggest that the high tolerance of I. cairica to key stress factors (e.g., salinity and herbivory) contributes to its invasion into salt marshes. For I. cairica, a trade-off in resource reallocation may allow increased resources to be allocated to tolerance and growth. This may contribute to a secondary invasion into stressful habitats. Finally, we suggest that I. cairica could spread further and successfully occupy salt marshes, and countermeasures based on herbivory could be ineffective for controlling this invasion.

Lineage and latitudinal variation in Phragmites australis tolerance to herbivory: implications for invasion success

“…Although populations sourced from the invaded range tend to be more tolerant than populations sourced from the native range (Abhilasha and Joshi , Wang et al , Liao et al , Zhang et al ; but see Bossdorf et al , de Jong and Lin ), understanding how tolerance to herbivory mediates invasion success requires a comparison between co‐occurring native and invasive species that share herbivore communities. Many fewer studies have compared tolerance between co‐occurring congeneric or confamilial pairs of native and invasive species, with findings of greater tolerance in invasive species (Ashton and Lerdau , Liu et al ), native species (Zas et al ), or no differences between them (Engelkes et al , Lurie et al ). Our approach is unique in that we compare conspecific native and invasive populations within the invaded range, and we found that native populations tolerate herbivory better on average than invasive populations.…”

Rapid evolution of dispersal‐related traits during range expansion of an invasive vine Mikania micrantha

“…In fact, selective pressures of both abiotic (e.g. resources availability, Liu et al , and climate, Monty et al ) and biotic (e.g. interactions with heterospecifics and other trophic levels, Diez et al , Kelehear et al , Lankau ) factors could shift and work on invasive populations toward the range edge, in addition to the spatial selection process.…”

The Invasion of Coastal Areas in South China by Ipomoea cairica May Be Accelerated by the Ecotype Being More Locally Adapted to Salt Stress

“…We separated the seedlings from each ecotype into two groups, with 10 replicates for each group; one group was watered daily with pipe water, and the other group was watered daily with 4 g L -1 NaCl solution. We used this salt concentration to simulate the salinity of the local sea [ 25 , 26 ]. After three months of plant growth, we selected at least 3 pots from each treatment for measurement of the photosynthesis.…”

“…This species is usually observed in farmlands, forest edges, roadsides, abandoned land, and other habitats without salt stress in introduced ranges. However, recent reports suggest the species is expanding into coastal areas and may cause a successful secondary invasion [ 25 , 26 ]. The reason for its new expansion into salt-stressed habitats has yet to be investigated.…”