The status of the name Alysium holtingii C. Agardh, a red alga described from Brazil, and a depiction of the type specimen

BIOLOGICAL SCIENCES   The status of the name Alysium holtingii C. Agardh, a red alga described from Brazil, and a depiction of the type specimen     Michael J. Wynne Department of Ecology and Evolutionary Biology and Herbarium, University of Michigan, Ann Arbor, Michigan 48109, U.S.A. Correspondence to     ABSTRACT The type specimen of the red alga Alysium holtingii C. Agardh, described from Brazil, is located in the Lund Herbarium, and it is depicted for the first time in a publication. It is taxonomically identical to Dichotomaria obtusata (J. Ellis and Solander) Lamarck and thus can be treated as a later taxonomic synonym. Alysium is regarded as congeneric with Dichotomaria. Key words: Alysium, Brazil, Dichotomaria obtusata, red algae, taxonomy, type specimen. RESUMO O espécime tipo da alga vermelha Alysium holtingii C. Agardh, descrito para o Brasil, está localizado no Herbário Lund, e é aqui apresentado. Ele é taxonomicamente idêntico a Dichotomaria obtusata (J. Ellis e Solander) Lamarck e portanto deve ser tratado como um sinônimo taxonômico posterior. Alysium é considerado como congenérico com Dichotomaria. Palavras-chave: Alysium, Brasil, Dichotomaria obtusata, algas vermelhas, taxonomia, espécime tipo.     INTRODUCTION AND BACKGROUND In recent years the red algal genus Galaxaura Lamouroux (1812) has been shown to be heterogeneous. Tricleocarpa was proposed by Huisman and Borowitzka (1990) as a segregate genus from Galaxaura, and Dichotomaria Lamarck (1816), long regarded as congeneric with Galaxaura, has been reinstated (Huisman et al.2004). In the ongoing revision of the family Galaxauraceae (Wang et al. 2005), the status of the ill-known genus Alysium deserves attention. Alysium was established by C. Agardh (1823), with the single species A. holtingii C. Agardh ("Ulva holtingii Mert. msc.") from the coast of Brazil, the specimen having been sent by Mertens to Agardh. Although the genus had only a brief description, the single species was provided with a more detailed account. C. Agardh (1824) repeated the name in his 'Systema algarum'. Sprengel (1827) recognized the genus, referring to two species, the original species A. holtingii and a new species, A. perrini Sprengel from the West Indies. But because the legitimate and available name Galaxaura oblongata (J. Ellis and Solander) J.V. Lamouroux was cited after A. perrini, it is an illegitimate name. Léman (1828) referred to Alysium holtingii as a plant from Brazil distinguished by its membranous, hollow, inflated frond, provided with constrictions, giving it an articulated aspect as well as by its reticulate, pentagonal covering. In their account of Alysium holtingii (as " Hoeltingii"), Martius et al. (1833) said it was discovered by "Hoelting" on the ocean shore near Sebastianópolis. It is not clear how they were able to provide this more precise information about the type locality. Sebastianópolis is an earlier name for Rio de Janeiro, or officially "São Sebastião do Rio de Janeiro". Martens' (1870) summary of records of Brazilian algae included Galaxaura obtusata with Alysium holtingii listed as a synonym, and he referred to the record of A. holtingii from "Rio" by Martius et al. (1833). Decaisne (1842) recognized Galaxaura and placed both Alysium C. Agardh and Dichotomaria Lamarck(1816) in its synonymy. Decaisne (1842) treated Alysium holtingii (as "Hottingii") as conspecific with Galaxaura obtusata (J. Ellis and Solander) Lamouroux (1816). Kützing (1843) altered Agardh's orthography of the name to Halysium, a name that was already occupied by a genus of hyphomycetous fungi (Corda 1837). Kützing assigned the genus to the family Lemaneaceae ['Familia XXXVII. Lemanieae'] and recognized a total of ten species. The first of these was H. holtingii, with "Alysium holtingii Ag." cited, and significantly "Corallina obtusata Ellis and Solander Tab. 22, Fig. 2" was listed as a taxonomic synonym. Kützing also indicated "Westindien: Mertens! (Herb. berol.)", revealing that he had seen Mertens' authentic material then in the Berlin Herbarium. The other species that were placed in Halysium were: H. oblongatum (J. Ellis and Solander) Kützing, H. cylindricum (J. Ellis and Solander) Kützing, H. rugosum (J. Ellis and Solander) Kützing, H. marginatum (J. Ellis and Solander) Kützing, H. fruticulosum (J. Ellis and Solander) Kützing, H. lapidescens (J. Ellis and Solander) Kützing, H. induratum (J. Ellis and Solander) Kützing, H. lichenoides (J. Ellis and Solander) Kützing, and the new species H. canaliculatum Kützing, that was described from the coast of Brazil. All of these species occurred in the tropical western Atlantic (West Indies, the Bahamas, Jamaica, Brazil, or "Antillenmeer"). Halysium rugosum was the only one of these species depicted by Kützing (1843, Pl. 43, Fig. 1). Kützing (1849, 1858) subsequently followed Decaisne (1842) in treating these species as belonging to the genus Galaxaura. His list included the species Galaxaura canaliculata (Kützing) Kützing (1849). Decaisne's (1842) inclusion of Alysium in Galaxaura has also been followed by Schmitz and Hauptfleisch (1897),De Toni (1897), and Kylin (1956). J.G. Agardh (1876) treated his father's genus Alysium as a new subgenus of Galaxaura, and he assigned the following three species to this subgenus: G. obtusata, G. umbellata (Esper) J.V. Lamouroux, and G. decaisnei J. Agardh. Two varieties, a and b, were recognized within Galaxaura obtusata: a Opuntioides included Corallina obtusata J. Ellis and Solander and thus would be the nominate variety; b oblongata included Corallina oblongata J. Ellis and Solander (1786) as well as Alysium holtingii C. Agardh. At present, Corallina oblongata is placed in Tricleocarpa,where it is treated as conspecific with T. fragilis (Linnaeus) Huisman et Townsend (1993). Therefore, if J. Agardh's (1876) treatment of A. holtingii in the synonymy of G. obtusata (J. Ellis and Solander) Lamouroux [var.] oblongata (J. Ellis and Solander) J.G. Agardh is correct, then the generic name Alysium would predate Tricleocarpa Huisman and Borowitzka (1990). On the other hand, if Alysium holtingii is a taxonomic synonym of Corallina obtusata, which is now Dichotomaria obtusata (J. Ellis and Solander) Lamarck, then Alysium can be relegated to synonymy with Dichotomaria. The detailed floristic accounts by Taylor (1960) and Oliveira (1977) made no specific mention of Alysium holtingii C. Agardh, nor did the historical accounts by Taylor (1931) and Joly (1952) refer to C. Agardh's Alysium holtingii. The fact that the type specimen of A. holtingii has never been depicted in the literature motivated me to locate it and also to determine whether its taxonomic assignment lies with Tricleocarpa fragilis or Dichotomaria obtusata.   OBSERVATIONS The type specimen of Alysium holtingii (Fig. 1) was located in the Agardh Herbarium (as No. 32432) inLund, Sweden, and rece (...truncated)