Megathyrsus maximus is nonnative in the neotropics, with a tall form that is commonly used as a forage grass and a smaller-statured form that is considered invasive in south Texas, USA. Biological control researchers are challenged to find an agent that will attack the short form, but not the desirable tall form in other parts of the neotropics. We conducted molecular analyses on 155 Megathyrsus maximus samples from its native range in Africa and compared them with U.S. short-form samples to help determine the geographic origins of its invasion. We found eight distinct genotypes in 34 short-form samples from Texas and Florida, USA. The highest genetic similarity of invasive samples was with plants from South Africa, while highest matches for the desirable tall form were from Kenya, Uganda, Ivory Coast, and Zambia. Ongoing biological control agent exploration and research has found agents from Kenya that are associated with an M. maximus genotype not well matched to the invasive short form, thus leading to a lack of rearing success. Two eriophyoid mite agents from the genetic match locality in South Africa have been evaluated but are not sufficiently host specific, as they develop on both the short and tall forms. Additional exploration is needed at the genetic match populations in South Africa to discover and evaluate potential biological control agents for the invasive form of M. maximus.

Megathyrsus maximus在新热带地区是非本地的，具有通常用作饲料草的高大形式和在美国德克萨斯州南部被认为是侵入性的身材较小的形式。生物控制研究人员面临的挑战是要找到一种能攻击矮型的药剂，而不是新热带其他地区理想的高型。我们对 155条巨嘴鱼进行了分子分析来自其在非洲本土的样本，并将它们与美国的简短样本进行比较，以帮助确定其入侵的地理起源。我们在来自美国德克萨斯州和佛罗里达州的 34 个简短样本中发现了八种不同的基因型。入侵样本的最高遗传相似性来自南非的植物，而与理想高大形态的最高匹配来自肯尼亚、乌干达、科特迪瓦和赞比亚。正在进行的生物控制剂探索和研究已发现来自肯尼亚的与M. maximus相关的药剂基因型与侵入性短型不匹配，因此导致缺乏成功饲养。已经评估了来自南非遗传匹配地区的两种类斑螨剂，但它们的宿主特异性不够，因为它们在短型和高型上都发育。需要对南非的遗传匹配种群进行进一步的探索，以发现和评估潜在的生物控制剂，用于入侵型大孢子虫。