To expand knowledge of Pseudo-nitzschia species in the Southeast Pacific, we isolated specimens from coastal waters of central Chile (36°S–30°S), the Gulf of Corcovado, and the oceanic Robinson Crusoe Island (700 km offshore) and grew them into monoclonal strains. A total of 123 Pseudo-nitzschia strains were identified to 11 species based on sequencing of the ITS region of the nuclear rDNA and on ultrastructural and morphometric analyses of the frustule in selected representatives of each clade: P. australis, P. bucculenta, P. cf. chiniana, P. cf. decipiens, P. fraudulenta, P. hasleana, P. multistriata, P. plurisecta, P. cf. sabit, the new species P. dampieri sp. nov., and one undescribed species. Partial 18S and 28S rDNA sequences, including the hypervariable V4 and D1–D3 regions used for barcoding, were gathered from representative strains of each species to facilitate future metabarcoding studies. Results showed different levels of genetic, and at times ultrastructural, diversity among the above-mentioned entities, suggesting morphological variants (P. bucculenta), rapidly radiating complexes with ill-defined species boundaries (P. cf. decipiens and P. cf. sabit), and the presence of new species (P. dampieri sp. nov., Pseudo-nitzschia sp. 1, and probably P. cf. chiniana). Domoic acid (DA) was detected in 18 out of 82 strains tested, including those of P. australis, P. plurisecta, and P. multistriata. Toxicity varied among species mostly corresponding to expectations from previous reports, with the prominent exception of P. fraudulenta; DA was not detected in any of its 10 strains tested. In conclusion, a high diversity of Pseudo-nitzschia exists in Chilean waters, particularly offshore.

为了扩大对东南太平洋拟菱形藻物种的了解，我们从智利中部（南纬 36°–30°）、科尔科瓦多湾和罗宾逊·克鲁索岛（离岸 700 公里）的沿海水域分离了标本，并在其中生长将它们转化为单克隆菌株。根据核 rDNA ITS 区域的测序以及对每个进化支选定代表的硅藻壳的超微结构和形态分析，总共 123 个拟菱形藻菌株被鉴定为 11 个物种：P. australis、P. bucculenta 、P .参见 奇尼亚纳，P. cf。decipiens、P. fakeulenta、P. hasleana、P. multistriata、P. plurisecta、P. cf。sabit，新种P. denpieri sp。十一月，和一个未描述的物种。从每个物种的代表性菌株中收集了部分 18S 和 28S rDNA 序列，包括用于条形码的高变 V4 和 D1-D3 区域，以促进未来的元条形码研究。结果显示上述实体之间存在不同水平的遗传多样性，有时是超微结构多样性，表明形态变异（P. bucculenta），快速辐射复合体，物种边界不明确（P. cf. decipiens和P. cf. sabit）），以及新物种的存在（P.dampieri sp.nov.、Pseudo -nitzschia sp.1 ，可能还有P.cf.chiniana）。在 82 个测试菌株中，有 18 个菌株检测到软骨藻酸 (DA)，其中包括P. australis、P. purisecta和P. multistriata。不同物种的毒性各不相同，大部分与之前报告的预期相符，但P. frugulenta是一个明显的例外；在所测试的 10 个菌株中均未检测到 DA。总之，智利水域，特别是近海，存在高度多样性的拟菱形藻。