(2902) Proposal to conserve the name Leptomitus with a conserved type (Leptomitales, Peronosporophyceae, Saprolegniophyta (Algae s.l.))

Abstract

(2902) Leptomitus C. Agardh, Syst. Alg.: xxiii, 47 (‘49’). Mai–Sep 1824, nom. cons. prop. Typus: L. lacteus (Roth) C. Agardh (Conferva lactea Roth), typ. cons. prop. The former oomycete genus Leptomitus C. Agardh (Syst. Alg.: xxiii, 47 [‘49’]. 1824) forms one of the most important phylads of the class Peronosporophyceae M.W. Dick (Stramin. Fungi: 289. 2001, as ‘Peronosporomycetes’), and commonly constitutes a distinct family Leptomitaceae Kütz. (Phycol. General.: 147. 1843, as ‘Leptomiteae’) and order Leptomitales Kanouse (in Amer. J. Bot. 14: 295. 1927) (Sparrow, Aquatic Phycomyc.: 871–873. 1960; Kussakin & Drozdov, Filema Organich. Mira 2: 251. 1998; Riethmüller & al. in Canad. J. Bot. 77: 1795. 2000 (‘1999’); Frey in Engler, Syllabus, ed. 13, 1(1): 100. 2012; Marano & al. in Jones & Pang, Mar. Fungi: 190. 2012; Beakes & Thines in Archibald & al., Handb. Protists: 41. 2016). These microorganisms are currently classified outside the Kingdom Fungi, and in this connection, they are placed within the crown of algal phylads of chromalveolates (Adl & al. in J. Eukar. Microbiol. 59: 454. 2012, 66: 40. 2018; Beakes & al. in Protoplasma 249: 3–19. 2012, in McLaughlin & Spatafora, Mycota 7A: 39–97. 2014; Wijayawardene & al. in Mycosphere 11: 1060–1456. 2020), generally treated as “ambiregnal” botanical and protozoological taxa at the rank of phylum Saprolegniophyta Karpov (Sist. Protistov: 120. 1990, as ‘Saprolegnia’), pro zool. phyl. (Kussakin & Drozdov, l.c.: 246, as ‘Saprolegniophyles’) or subphylum Peronosporophytina M.W. Dick (l.c.: 288, as ‘Peronosporomycotina’) [terminations modified to reflect treatment under the ICN (Turland & al. in Regnum Veg. 159. 2018: Art. 45.1) and treatment as Algae and not Fungi]. The species circumscription of the genus is variable from 9 to 10 species to monotypic (Sparrow, l.c.; Dick, l.c.). Numerous binomials (more than 20) are also ill-known, being schematically described in the 19th century, but are mostly unidentifiable and remain nomina dubiosa. Unfortunately, when initially proposed, the genus Leptomitus inadmissibly included the original types of two (sic!) previously validly published oomycete generic names, Achlya Nees (in Nova Acta Phys.-Med. Acad. Caes. Leop.-Carol. Nat. Cur. 11: 514. 1823: A. prolifera Nees) and Saprolegnia Nees (in Nova Acta Phys.-Med. Acad. Caes. Leop.-Carol. Nat. Cur. 11: 513. 1823: S. molluscorum Nees, nom. illeg. [Conferva ferax Gruith. ≡ S. ferax (Gruith.) Kütz.]). Achlya and Saprolegnia are now considered to be distinct, well-circumscribed genera and are in current use (Dick, l.c.; Beakes & Thines, l.c.). So, Leptomitus is a nomenclaturally superfluous and illegitimate generic name since when established it included types of previously validly published generic names. To overcome this nomenclatural illegitimacy, it is necessary to conserve the generic name with an established element as type (Leptomitus lacteus (Roth) C. Agardh [Conferva lactea Roth]) to allow its further use in botanical systematics and to maintain the nomenclatural stability and established custom in the formerly oomycetous nomenclature. Since due to some tradition to treat oomycetes as straminipilous Protista that continues, though archaically, to the present (Karpov, l.c. 1990, Sist. Protistov, ed. 3: 168. 2000; Kussakin & Drozdov, l.c.; Beakes & Thines, l.c), the same proposal will be submitted to the International Commission on Zoological Nomenclature asking for analogous action to legitimize Leptomitus as a genus in (proto)zoological nomenclature (ICZN) for those researchers who will permissibly continue to treat these microorganisms as protists (so-called “ambiregnal” organisms). ABD, https://orcid.org/0000-0003-0089-5919 It is a pleasure to thank Valentina Bublik (Fundamental Botanical Library of the National Institute of Carpology, Moscow) for bibliographic assistance.