Taxonomic and life cycle reappraisals of the marine basidiomycete <i>Nia vibrissa</i> complex, with descriptions of three new <i>Nia</i> species

The marine basidiomycete Nia vibrissa has been regarded as a species complex, possibly including several species, because morphological variations in fruitbody, spore, and spore appendage have been observed in materials from worldwide collections. Using more than 50 monosporic isolates of N. vibrissa–like fungi mainly obtained from Japanese beach coasts, we investigated their molecular phylogeny, morphological characteristics, mating compatibility, nuclear behavior during spore formation, and life cycles. Molecular phylogenetic analyses separated the examined strains into seven clades. Each clade of fungi exhibited distinctive characteristics in fruitbodies and spores produced by culturing monokaryotic strains and mated dikaryotic strains; these characteristics included the color of fruitbodies, apical structure of peridial hair hyphae, spore shape, and apical structure of spore appendages. Mating tests of monokaryotic strains demonstrated mating compatibility between strains within a clade and incompatibility among clades. Therefore, each clade of fungi was phylogenetically, morphologically, and biologically recognized as a different Nia species. Observation of the type specimen of N. vibrissa revealed a tiny T-shaped apical structure of spore appendages—not mentioned in the original description—that is unique to the species. This finding, together with the original description, suggests that our studied strains include N. aff. vibrissa, whose morphology is mostly identical to N. vibrissa sensu stricto, and three new species. Thus, we describe three new Nia species and propose emendation of the descriptions of the genus Nia. Culture-based studies have demonstrated that Nia species have both sexual and asexual morphs that produce morphologically similar fruitbodies (basidiomata and conidiomata) and spores (basidiospores and conidia). Because it has both morphs forming appendaged waterborne basidiospores and conidia, Nia must be the most well-adapted marine basidiomycete, ensuring the continuation of new generations by two morphs, while distributing in and inhabiting numerous marine environments.海洋担子菌（marine basidiomycete）**Nia vibrissa**（Nia vibrissa）长期以来被视为一个物种复合群（species complex），可能包含多个物种，因为全球馆藏材料中已观察到其子实体、孢子及孢子附属物的形态变异。本研究以主要采自日本沿海沙滩的50余株类**Nia vibrissa**真菌单孢分离物（monosporic isolates）为材料，对其分子系统发育（molecular phylogeny）、形态特征、交配亲和性、孢子形成过程中的核行为及生活史展开了研究。分子系统发育分析将供试菌株划分为7个支系（clades）。各支系真菌在单核菌株培养、交配后双核菌株所产生的子实体与孢子上均表现出独特性状，包括子实体颜色、包被毛菌丝（peridial hair hyphae）顶端结构、孢子形态及孢子附属物顶端结构。单核菌株的交配试验表明，同一支系内的菌株间存在交配亲和性，而不同支系间则不亲和。因此，各支系真菌在系统发育、形态学及生物学上均被界定为独立的**Nia**属物种。对**Nia vibrissa**模式标本（type specimen）的观察显示，其孢子附属物存在一种原始描述未提及的微小T形顶端结构，该结构为该物种所特有。结合原始描述，该发现提示本研究的菌株包含形态与狭义**Nia vibrissa**（N. vibrissa sensu stricto）基本一致的亲和**N. vibrissa**（N. aff. vibrissa）类群，以及3个新种（new species）。据此，本研究描述了3个**Nia**属新种，并提出对**Nia**属的分类修订。基于培养的研究表明，**Nia**属物种兼具有性与无性形态，可产生形态相似的子实体（担子果（basidiomata）与分生孢子果（conidiomata））及孢子（担孢子（basidiospores）与分生孢子（conidia））。由于该属同时具备可产生具附属物水生担孢子与分生孢子的两种形态，**Nia**属应是适应性最强的海洋担子菌类群，可通过两种形态延续后代，并广泛分布并栖息于各类海洋环境中。