Capitulum density-dependent effects generate peak seed yield at an intermediate density of a Tibetan lotus  

作　　者：Xinqiang Xi Junpeng Mu Youhong Peng Nico Eisenhauer Shucun Sun 

机构地区：[1]Center for Ecological Studies,Chengdu Institute of Biology,9 Section 4 Renminnan Rd,Chengdu 610041,China [2]Department of Biology,Nanjing University,22 Hankou Road,Nanjing 210093,China [3]German Centre for Integrative Biodiversity Research(iDiv)Halle-Jena-Leipzig,Deutscher Platz 5e,04103 Leipzig,Germany [4]Institute of Biology,University of Leipzig,Johannisallee 21,04103 Leipzig,Germany

出　　处：《Journal of Plant Ecology》2016年第1期100-106,共7页植物生态学报（英文版）

基　　金：973 program(2013CB956300);National Science Foundation of China(31100397 and 3250004);‘Program for Changjiang Scholars and Innovative Research Team in University’(IRT_14R27).

摘　　要：Aims Theory suggests that species perform best at intermediate densities,where density-dependent facilitation and antagonism are balanced,but empirical evidence is scarce,particularly in plants.In a selfincompatible perennial herb(Saussurea nigrescens),whose recruitment heavily relies on seed output,we test whether both intraspecific facilitation and antagonism significantly affect seed production,resulting in highest seed yield at an intermediate capitulum density.Methods Plots with different S.nigrescens densities were sampled in an Eastern Tibetan meadow during the growing season of 2012 to investigate the relationships between capitulum density and pollinator visitation rate,seed set ratio,parasite ratio,seed damage ratio,and capitulum size.Both simple linear and quadratic models were employed to determine the shape of relationships.Important Findings In line with general theory,hump-shaped relationships of capitulum density versus seed set ratio and number of florets per capitulum indicate intraspecific facilitation in sparse populations,which can be attributed to positive density-dependent pollinator visitation and the amelioration of detrimental physical factors.However,the proportion of seeds damaged by pre-dispersal predators increased monotonically with capitulum density,which may have—in combination with increased intraspecific competition for light and soil nutrients—resulted in density-dependent antagonism.Both positive and negative density-dependent agents acted simultaneously throughout the density range investigated and led to the highest seed yield at intermediate density levels in the Tibetan lotus.More efforts concurrently exploring the two effects are needed to facilitate understanding species abundance and community structure.

关 键 词：density-dependent effect FACILITATION competition seed pre-dispersal predator POLLINATION 

分 类 号：D67[政治法律—政治学]