Population Genetic Diversity Influences The Colonization Success Of Alternanthera Philoxeroides

The ecological effect of genetic diversity in population has been a hot research topic in ecology. In the field of invasion ecology, researchers have focused on the genetic structure of alien species for a long time, but they were interested in the long term effect of genetic diversity on population rather than short-term effect in colonization of invasive process. Here, we test whether population-level characteristics, specifically genetic diversity, can influence colonization ability on a short-term ecological timescale. Within experimentally manipulated genotype richness in populations of the Alternanthera philoxeroides and measured the fitness variables such as biomass, shoot number and length of root etc. four times in the growing season, we test the short-term effect of genetic diversity in the population. Monte Carlo simulation and the analysis of net effect were used to identify the additive and non-additive mechanism of diversity. The result is summarized as follows:(1) Increased genetic diversity within founding populations of A. philoxeroides significantly increased population fitness and production.Increased genetic diversity significantly increased total biomass, below ground biomass, length and number of storage root, but no significant increasing in shoot number and internode number. Above ground biomass was not significant in first three measurements but significant in the last measurement. The result suggests that genetic diversity could influence population fitness and production of A. philoxeroides.(2) The population effect of genetic diversity mostly infuluences A. philoxeroides population by non-additive mechanism. The result of Monte Carlo simulation and analysis of net effect shows genetic diversity affect A. philoxeroides by some non-additive mechanism such as complementarity and facilitation. The magnitude of these mechanisms increased with the increasing of genetic diversity.(3) A. philoxeroides in polyculture allot more biomass to storage root than in monoculture. The analysis of biomass proportion showed that storage root biomass proportion significant higher in polyculture than monoculture in first three harvests but no significance in last harvest. This result suggests A. philoxeroides allotted more biomass to storage root rather than shoot in polyculture than in monoculture.Our result suggests that increasing genetic diversity may lead to higher fitness and invasiveness of A. philoxeroides which will influence the colonization success. Since the genetic diversity of A. philoxeroides is very low in China, the damage caused by this invasive weed may be worse when it has higher genetic diversity. Genetic diversity may have important implications for predicting biological invasions when introduces a new species.