The red seaweed Hypnea pseudomusciformis has economic potential for mariculture as a source of carrageenan and other products. This work investigates this species along the Brazilian coastline by evaluating the effects of irradiance (40, 70, and 100 μmol photons m⁻² s⁻¹) on the number of differentiated branches (Br), growth rates (GR), photosynthesis parameters, and pigment content of tetrasporophytes from five distinct geographical populations extending from 5° to 27° S of latitude. The specimens showed intraspecific divergence for COI-5P marker, divided into three haplotypes with distinct geographical distribution. Although irradiance effects were significant only for GR and Br, intraspecific diversity was significant in all variables analyzed, with the haplotype of the tropical zone (5° to 12° S) displaying higher GR, Br, and maximum quantum yield (F_v/F_m) than the haplotype of the subtropical zone (23° to 27° S), which displayed higher pigment concentration. The geographic intermediate haplotype (19° S) displayed similar GR, Br, and F_v/F_m to the tropical haplotype, but similar pigment content to the subtropical haplotype. Our results indicate the presence of ecotypes within H. pseudomusciformis throughout its geographic distribution. Considering the set of physiological attributes, specimens from the tropical zone have higher potential for mariculture.

红海藻Hypnea pseudomusciformis作为角叉菜胶和其他产品的来源，具有海水养殖的经济潜力。这项工作通过评估辐照度（40、70和100μmol光子m ^{- 2} s ^-1），研究了从5°到27°S纬度的五个不同地理种群的四孢子植物的分化分支数（Br），生长速率（GR），光合作用参数和色素含量。标本显示出COI-5P标记的种内差异，分为具有不同地理分布的三种单倍型。尽管辐照效应仅对GR和Br显着，但种内差异在所有分析的变量中均显着，热带区域（5°至12°S）的单倍型显示出更高的GR，Br和最大量子产率（F _v / F_米），而不是亚热带区域（23°至27°S）的单体型，后者显示出更高的颜料浓度。地理中间单倍型（19°S）显示出与热带单倍型相似的GR，Br和F _v / F _m，但与亚热带单倍型相似的色素含量。我们的研究结果表明假性嗜血杆菌在其整个地理分布中存在生态型。考虑到生理属性的集合，热带地区的标本具有更高的海水养殖潜力。