以天津的入侵植物黄顶菊〔Flaveria bidentis （Linn.） Kuntze〕为研究对象，对其植物学性状和种子传播特性进行观察和统计，并基于ITS序列构建黄顶菊与菊科（Asteraceae）其他植物的系统进化树。观察结果表明：黄顶菊株高0.3～2.0 m、茎直径1.62～5.45 mm，根系发达；每个头状花序包含小花1～20朵，其中，舌状花1朵、管状花0～19朵；成熟种子黑色、披针状、扁平、无冠毛，种皮具10棱痕。黄顶菊单株有小花8 302朵、饱满种子6 698粒，结实率为80.7％；种子千粒质量0.224 0 g，种子萌发势和萌发率分别为86.0％和98.6％。黄顶菊种子的水平漂移距离随风速增大（0.7～3.5 m·s^-1）逐渐增大且差异显著（P＜0.05），其中，在3.5 m·s^-1风速（相当于自然界中三级风）下，种子的水平漂移距离最大（60.54 cm）。在静止和搅拌条件下分别浸泡6～36 h，漂浮种子数存在明显差异；在搅拌条件下，随搅拌次数和浸泡时间的增加，漂浮种子数逐渐减少，浸泡36 h（6次搅拌）后已无漂浮种子；而在静止状态下，浸泡36 h后仍无种子下沉，漂浮种子数保持恒定。ITS片段扩增及系统进化树分析结果表明：供试黄顶菊ITS片段长度为682 bp，含有变异位点310个、简约信息位点284个、保守位点242个和自裔位点26个，T（U）、C、A和G碱基数量分别占碱基总数的26.6％、23.6％、24.0％和25.8％，且供试黄顶菊与原产地（南美洲）黄顶菊的ITS序列完全一致；在NJ系统进化树上，供试黄顶菊与原产地黄顶菊的遗传距离最近，而与其他4种供试菊科植物以及黄顶菊属（Flaveria Jussieu）及其近缘属植物的遗传距离均较远。综合分析结果表明：黄顶菊结实率较高、单株种子数多，种子萌发率较高且具有一定的随风和随水流传播的能力；供试黄顶菊的株高和头状花序所包含的管状花数均高于原产地，与其生境适应性有关。依据观察结果，对黄顶菊的防除提出了合理建议。

Taking invasive plant Flaveria bidentis （Linn.） Kuntze from Tianjin as research object， its botanical characters and seed propagation characteristics were observed and counted， and phylogenetic trees of F. bidentis and other species in Asteraceae were constructed based on ITS sequences. The observation results show that the plant height of F. bidentis is 0.3-2.0 m， stem diameter is 1.62-5.45 mm， and root system is developed； each capitulum contains 1-20 florets， in which， there are 1 ligulate floret and 0-19 tubular florets； mature seed is black， lanceolate， flat， uncrested， and seed coat has 10 ridges. Individual of F. bidentis has 8 302 florets and 6 698 plump seeds， and setting rate is 80.7％； 1 000-grain mass of seed is 0.224 0 g， and germination potential and germination rate of seed are 86.0％ and 98.6％， respectively. The horizontal dispersal distance of F. bidentis seed gradually increases with the increase of wind speed （0.7-3.5 m·s^-1） and the difference is significant （P＜0.05）， in which， that of seeds is the largest （60.54 cm） at 3.5 m·s^-1 wind speed （equivalent to the thirdorder wind in nature）. There are obvious differences in number of floating seed after soaking for 6-36 h under motionless and stirring conditions， respectively； under stirring condition， with the increase of stirring times and soaking time， the number of floating seed gradually decreases， and there is no floating seed after soaking for 36 h （6 times of stirring）； while under motionless condition， seeds do not sink after soaking for 36 h， and the number of floating seed remains constant. The results of ITS fragment amplification and phylogenetic tree analysis show that ITS fragment length of F. bidentis tested is 682 bp， which contains 310 mutation sites， 284 simple information sites， 242 conservative sites and 26 self-descendant sites， the numbers of T （U）， C， A and G bases account for 26.6％， 23.6％， 24.0％ and 25.8％ of total number of bases， respectively， and the ITS sequence of F. bidentis tested is identical with that of native （South America） F. bidentis； in NJ phylogenetic tree， the genetic distance between F. bidentis tested and native F. bidentis is the closest， while that with other 4 species tested in Asteraceae, and Flaveria Jussieu and its related genera plants is far. The result of comprehensive analysis shows that setting rate of F. bidentis is higher， number of seeds per plant is large， seed germination rate is higher and has a certain ability of propagation with wind and water； plant height of F. bidentis tested and number of tubular florets in its capitulum are higher than those in native place， which is related to its habitat adaptability. According to the observation results， reasonable suggestions are put forward for the control of F. bidentis.