Light limitation and litter of an invasive clonal plant, Wedelia trilobata, inhibit its seedling recruitment.
OBJECTIVE
Invasive clonal plants have two reproduction patterns, namely sexual and vegetative propagation. However, seedling recruitment of invasive clonal plants can decline as the invasion process proceeds. For example, although the invasive clonal Wedelia trilobata (Asteraceae) produces numerous seeds, few seedlings emerge under its dense population canopy in the field. In this study it is hypothesized that light limitation and the presence of a thick layer of its own litter may be the primary factors causing the failure of seedling recruitment for this invasive weed in the field.


METHODS
A field survey was conducted to determine the allocation of resources to sexual reproduction and seedling recruitment in W. trilobata. Seed germination was also determined in the field. Effects of light and W. trilobata leaf extracts on seed germination and seedling growth were tested in the laboratory.


RESULTS
Wedelia trilobata blooms profusely and produces copious viable seeds in the field. However, seedlings of W. trilobata were not detected under mother ramets and few emerged seedlings were found in the bare ground near to populations. In laboratory experiments, low light significantly inhibited seed germination. Leaf extracts also decreased seed germination and inhibited seedling growth, and significant interactions were found between low light and leaf extracts on seed germination. However, seeds were found to germinate in an invaded field after removal of the W. trilobata plant canopy.


CONCLUSIONS
The results indicate that lack of light and the presence of its own litter might be two major factors responsible for the low numbers of W. trilobata seedlings found in the field. New populations will establish from seeds once the limiting factors are eliminated, and seeds can be the agents of long-distance dispersal; therefore, prevention of seed production remains an important component in controlling the spread of this invasive clonal plant.
Institute of Environment and Ecology, School of the Environment and Safety Engineering, Jiangsu University, Zhenjiang 212013, China.
Shan-Shan
SS
Qi
Institute of Environment and Ecology, School of the Environment and Safety Engineering, Jiangsu University, Zhenjiang 212013, China.
Zhi-Cong
ZC
Dai
West Palm Beach, FL 33413, USA.
Shi-Li
SL
Miao
World Agroforestry Centre (ICRAF), Central and East-Asia Office, Heilongtan, Kunming 650201, China Centre for Mountain Ecosystem Studies (CMES), Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China.
De-Li
DL
Zhai
Institute of Environment and Ecology, School of the Environment and Safety Engineering, Jiangsu University, Zhenjiang 212013, China.
Chun-Can
CC
Si
Institute of Environment and Ecology, School of the Environment and Safety Engineering, Jiangsu University, Zhenjiang 212013, China.
Ping
P
Huang
College of Life Sciences, Hainan Normal University, Haikou 571158, China.
Rui-Ping
RP
Wang
Institute of Environment and Ecology, School of the Environment and Safety Engineering, Jiangsu University, Zhenjiang 212013, China Key Laboratory of Modern Agricultural Equipment and Technology, Ministry of Education & Jiangsu Province, Jiangsu University, Zhenjiang 212013, China ddl@ujs.edu.cn.
Dao-Lin
DL
Du
D000704:Analysis of Variance; D002681:China; D002999:Clone Cells; D018525:Germination / Q000187:drug effects / Q000528:radiation effects; D008027:Light; D010936:Plant Extracts / Q000494:pharmacology; D018515:Plant Leaves / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D057685:Plant Weeds / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D012100:Reproduction, Asexual; D036226:Seedlings / Q000187:drug effects / Q000254:growth & development* / Q000528:radiation effects; D031209:Wedelia / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects*
D010936:Plant Extracts
Asteraceae; Clonal plant ecology; Wedelia trilobata; biological invasion; invasive plant; leaf litter; light limitation; reproductive strategy; seedling recruitment inhibition