Evaluation of Extracts of Native and Non-Native Plant Species for the Suppression of Cogongrass （Imperata cylindrica L.）

Effects of the extracts of muhly grass （Muhlenbergia capillaries Lam.）, chenopodium （Chenopodium ambrosioides L.） and black walnut （Juglans nigra L.） on the growth of cogongrass （Imperata cylindrica L.） were studied. None purified extracts from these plant species were used to evaluate survival, shoot and root growth of cogongrass. Results of plant species extracts on the production of roots, shoot and rhizomes of cogongrass genets and ramets were determined on a weekly basis. The extracts significantly reduced the growth and survival of cogongrass when compared to the control. Results indicated that for the in vivo studies, chenopodium extracts, black walnut and muhly grass extracts reduced growth, root and shoot biomass of cogongrass by 50 %, 30 % and 41% respectively, compared to control at 8 weeks after planting. These studies indicated plant species with potential for the biological control of cogongrass, an invasive species in the Gulf Coast States.

Biodiversity and Invasibility: Distribution Patterns of Invasive Plant Species in the Himalayas, Nepal

Invasive plant species are exerting a serious threat to biological diversity in many regions of the world. To understand plant invasions this study aims to test which of the two plant invasiveness hypotheses; ‘low native diversity' vs. ‘high native diversity', is supported by the regional distribution patterns of invasive plant species in the Himalayas,Nepal. This study is based on data retrieved from published literatures and herbarium specimens. The relationship between invasive plant species distribution patterns and that of native plant species is elucidated by scatter plots, as well as by generalized linear models. The native plant species and invasive plant species have similar distribution patterns and the maximum number of invasive plant species is found in the same altitudinal range where the highest richness for native tree species is found. There is a clear trend of higher invasive plant richness in regions where native tree species richness is relatively high.Consequently, the native plant richness is highest in the central phytogeographic region, followed by the eastern and the western regions, respectively. The invasive plant species also follows a similar trend.Additionally, the invasive plant species richness was positively correlated with anthropogenic factors such as human population density and the number of visiting tourists. This study supports the hypothesis that ‘high native diversity' supports or facilitates invasive plant species. Further, it indicates that nativeand invasive plant species may require similar natural conditions, but that the invasive plant species seem more dependent and influenced by anthropogenic disturbance factors.

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.