Classical Taxonomv And Invasive Risk Assessment Of Amaranthus In China

Amaranthus with about 70 species is widely distributed in the world. Since its tiny flowers and seeds, it is too difficult to distinguish among the species in the genus. There are 17 species and 2 subspecies in China; but there are some confusing problems among the interspecies classification of Amaranthus. In addition, Amaranthus has caused some damage became invasion of the largest number of species as dominant in the genus in some reports of alien invasive plants. In this study, about 3000 related specimens of Amaranthus, with a total of 2752 samples, have been consulted in seven domestic herbaria. After extensive literature survey,16 species and 2 subspecies of 1000 specimens, with a total of 379 samples, have been collected through investigating at the field works in China. In order to make interspecies identification accurately and enrich the morphological description, the classical taxonomy studies in details have been adopted. These studies are based on anatomy of the pistillate flowers and seeds morphology through scanning electron microscopy (SEM). All research above can provide a theoretical basis about the genus for conducting cell biology, molecular system studies, and taking appropriate measures to control the manage. According to the biological and ecological characteristics of the genus, "Invasive risk assessment system of Amaranthus in China" has been established with other risk assessment systems as reference. The system can prevent the introduction of species of the genus and provide a basis of effective management measures. It also can be as a reference for the future establishment of alien invasive plants risk assessment system of dominant families or genera. The conclusions are achieved:1. There are few distinguishing feature for staminate flowers of species in the genus. The morphological characteristics of pistillate flowers has important significance in interspecies identification among the genus.2. The species of the genus can be identified based on reticulate features of seeds surface. The characteristics is significant discriminator of interspecies classification in the genus.3. After careful study, Amaranthus roxburghianus Kung should be used as a synonym of Amaranthus graecizans subsp. aschersonianus (Thell.) Costea, Brenner & Tardif. This study suggests that Amaranthus patulus Bertoloni should be as a synonym of Amaranthus hybridus L.4. "Invasive risk assessment system of Amaranthus in China" has been established with dividing the risk by four grades. The risk assessment scores for Grade D is from 0 to 35 points, which indicated that introduction of these species may be allowed. Amaranthus tenuifolius Willd., and Amaranthus tricolor L. are among the Grade D. The risk assessment scores for Grade C is from 35 to 40 points, which suggested that these species may be at risk and more research should be proceed before any introduction. Amaranthus polygonoides L., Amaranthus retroflexus var. delilei (Richter & Loret) Thellung, and Amaranthus caudatus L. for Grade C. The risk assessment scores from 40 to 50 points is for Grade B, which indicated a certain risk existed, and it needs to take appropriate quarantine and management measures in order to reduce introduction and its invasive impact. Amaranthus graecizans subsp. aschersonianus (Thell.) Costea, Brenner & Tardif, Amaranthus hypochondriacus L., Amaranthus dubius Martius ex Thellung, Amaranthus albus L., Amaranthus blitum L., Amaranthus blitoides S.Watson, and Amaranthus viridis L. are for Grade B. The risk assessment scores from 50 to 100 points is for Grade A, which indicated the high risk of invasion, and any introduction should be prohibited, and more important is necessary to take effective measures to control the species of the Grade A. Amaranthus powellii S. Watson, Amaranthus palmeri S. Watson, Amaranthus spinosus L., Amaranthus cruentus L., Amaranthus retroflexus L., and Amaranthus hybridus L. are for Grade A.