Harmful blooms formed by planktonic microalgae (HABs) in both freshwater and coastal waters regularly lead to severe mortalities of fish and invertebrates causing substantial economic losses of marine products worldwide. The mixotrophic haptophyte Prymnesium parvum is one of the most important microalgae associated with fish kills. Here 26 strains of P. parvum with a wide geographical distribution were screened for the production of prymnesins, the suspected causative allelochemical toxins. All investigated strains produced prymnesins, indicating that the toxins play an important role for the organism. The prymnesins can be classified into three types based on the length of the carbon backbone of the compound and each algal strain produced only one of these types. Biogeographical mapping of the prymnesin distribution indicated a global distribution of each type. In addition, phylogenetic analyses based on internal transcribed spacer (ITS) sequences revealed monophyletic origin of all prymnesin types and clades could therefore be defined based on the toxic compound. It might be that evolution of new species within the P. parvum species complex is driven by changes in toxin type or that they are a result of it. Such a correlation between chemotype and phylotype has never been documented before for a harmful microalga. Chemotaxonomy and ITS-type classification may thus be used to further delimit the P. parvum species complex.

淡水和沿海水域中的浮游微藻（HAB）形成的有害水华经常导致鱼类和无脊椎动物的严重死亡，从而造成全世界海洋产品的重大经济损失。混合营养的触藻植物小球藻是与杀鱼有关的最重要的微藻类之一。这里有26株小菜蛾对分布广泛的地区进行了筛查，以检测是否存在prymnesins，prymnesins是可疑的化感性化学毒素。所有调查的菌株均产生了木霉菌素，表明毒素对该生物体起着重要作用。基于化合物的碳主链的长度，木霉素可以分为三种类型，并且每种藻类菌株仅产生这些类型中的一种。Prymnesin分布的生物地理图谱表明每种类型的全局分布。另外，基于内部转录间隔区（ITS）序列的系统发育分析表明，所有Prymnesin类型和进化枝的单系起源都可以基于有毒化合物进行定义。这可能是新物种内进化P.孢子虫物种复合物是由毒素类型的变化驱动的，或者是它们的结果。化学型和系统型之间的这种相关性以前从未被有害微藻记载。因此，化学分类法和ITS类型分类可用于进一步界定小球藻物种复合体。