Genetic diversity and population structure of invasive and native populations of Erigeron canadensis L.

Invasive alien plants threaten biodiversity across the world.Erigeron canadensis(horseweed)is one of the most problematic agricultural weeds and represents a classic example of intercontinental invasion.Here,we studied the genetic diversity and population structure of invasive alien populations from the Jiangsu and Zhejiang Provinces in China and native populations from Alabama,in the USA.We used 10 polymorphic SSR loci to genotype 312 individuals from 5 native and 5 invasive populations to estimate the genetic diversity and structure.Invasive populations from Jiangsu and Zhejiang Provinces showed,on average,similar genetic diversity to native populations from Alabama,indicating no severe genetic bottlenecks during the invasion.STRUCTURE revealed that low population differentiation occurred,and that only two genetic groupings were detected in both native and invaded ranges.The high diversity observed in the invasive populations suggested multiple introductions and/or the introduction of genetically diverse propagules during initial colonization.Our study provides new insights toward understanding the invasion dynamics of this globally noxious weed in Eastern China.Preventing gene flow via seed dispersal between invasive and native populations should be examined to prevent the introduction and dispersal of herbicide-resistant individuals and inform management practices.

Structure and genetic diversity of natural populations of Guadua weberbaueri in the southwestern Amazon,Brazil

The Brazilian state of Acre has an extensive natural reserve of bamboo,making it one of the largest in loco gene banks.The aim of this study was to characterize the structure and genetic diversity of Guadua weberbaueri Pilg.in two populations,one native(FAPB)and the other anthropized(FAPBA),using ISSR markers.The results show that the FAPB population exhibited higher values for all estimates of population diversity.However,the FAPBA population also showed high heterozygosity,corroborated by estimated gene flow(Nm=3.9)between the populations.The study of the association between Nei’s genetic distances and the geographic distances between the populations were significantly correlated(r=0.45,p=0.01),corroborated by the dendrogram revealing two distinct groups corresponding to the collection sites,without mixing classes between populations in the same group.As for the coancestry coefficient,pairs of individuals in the first distance class were positive and significant,indicating that plants that are geographically closer share common alleles with a frequency greater than by chance,which means that there is a tendency that geographically closer individuals are related.Individuals presented similar genetic structure when the geographical distance between them was up to 56 m for FAPB and up to 156 m for FAPBA.It was concluded that anthropized environments exhibit less genetic diversity than native environments,inferring risks for species conservation if appropriate and planned management techniques are not adopted.

Biotic Homogenization Caused by the Invasion of Solidago canadensis in China

Although studies argue that invasive species can cause biotic differentiation, some cases show that biological invasions actually decrease biodiversity through biotic homogenization. The concept of biotic homogenization through the invasion of a certain serious invasive plant species merit more studies. Hence, we used field surveys to quantitatively compare invasive populations of Solidago canadensis （SC） in China with the control sites （adjacent sites to SC present sites yet without the species） and SC native populations in the USA. We found that plant communities in SC invaded habitats shared similarities with those in SC native ranges. Bray-Curtis similarity clearly showed that the composition of plant communities in SC invaded habitats were similar to those in SC native ranges. Both in the native and introduced range, plant communities with SC present were characterized by SC being dominant, significantly lower species richness, or-diversity and p-diversity, as well as a decrease in the correlation coefficient between geographic distance and floristic similarities. SC favors fertile and moist loam habitat, while it dominated in various habitats in China, where more than 20 different dominants should have occurred. In conclusion, serious invasive species can quickly remodel and homogenize diverse communities by dominating them.