Introduction
The name Sergipea M. Cáceres et al. was recently established for a novel lineage of lichenized fungi in the Arthoniales, related to the genera Dichosporidium, Enterographa, and Erythrodecton (Aptroot et al. Reference Aptroot, Ertz, Lima, Jesus, Maia and Cáceres2013). The name is derived from the state of Sergipe in north-eastern Brazil, where the new genus was discovered.
While working on a database of neotropical crustose lichens, we found that the name Sergipea M. Cáceres et al. is a later homonym of Sergipea Regali et al., a genus of fossil pollen (see Discussion) described from the late Lower Cretaceous (Late Aptian to Early Albian; c. 113–109 mya) of north-eastern Brazil (Regali et al. Reference Regali, Uesugui and Santos1974). Sergipea sensu Regali et al. (Reference Regali, Uesugui and Santos1974) was originally established for two species, S. naviformis Regali et al. and S. variverrucata Regali et al., the first designated as generic type; four additional species, S. agadirensis Bettar & Meon, S. crassiverrucara Regali, S. simplex Regali, and S. tenuiverrucata Regali, were described later (Regali Reference Regali1987, Reference Regali1989; Bettar & Meon Reference Bettar and Meon2006). The genus was subsequently used in a variety of stratigraphic studies of north-eastern Brazil, with a stratigraphic zone even being named after one of the species (Carvalho Reference Carvalho2004; Heimhofer & Hochuli Reference Heimhofer and Hochuli2010; Arai et al. Reference Arai, Lana and Ferreira2013).
Since the original publication of Sergipea sensu Regali et al. (Reference Regali, Uesugui and Santos1974) is entirely in Portuguese, without any Latin diagnosis, one might assume the name is invalid. However, according to the International Code of Nomenclature for Algae, Fungi, and Plants (Melbourne Code; McNeill et al. Reference McNeill, Barrie, Buck, Demoulin, Greuter, Hawksworth, Herendeen, Knapp, Marhold and Prado2012), ICN Art. 39.1 “... does not apply to names of fossil-taxa ...”, and hence a “... validating description or diagnosis ... in any language is acceptable for them prior to 1996.” In addition, the protologue designated a generic type, required for valid publication of a genus name on or after 1 January 1958 (ICN Art. 40.1), and included two figures of the type species, thus also fulfilling the requirement for validity of including an illustration or figure when published on or after 1 January 1912 (ICN Art. 43.2).
As a consequence, the name Sergipea Regali et al. is valid and legitimate and the name Sergipea M. Cáceres et al. is a later homonym and illegitimate, requiring the introduction of a replacement name. We also took the opportunity to provide an updated phylogenetic analysis using available sequence data of the small subunit of the mitochondrial rDNA cistron (mtSSU).
Materials and Methods
Pertinent literature searches were carried out in Google Scholar (https://scholar.google.de) and on the pages of some of the journals of the original publications, such as the Boletim Técnico da Petrobras (http://vdpf.petrobras.com.br/vdpf/index.jsp), as well as the Paleobiology Database, Fossilworks, and the Paleobotany Database (see Discussion).
For the phylogenetic analysis, we downloaded 18 available sequences from Genbank for 11 species in the clade containing Enterographa and allied genera (here named the Enterographa clade), namely Dichosporidium boschianum (Mont.) G. Thor (1 sequence), D. brunnthaleri (Zahlbr.) G. Thor (1), D. nigrocinctum (Ehrenb.) G. Thor (2), Enterographa crassa (DC.) Fée (4), E. hutchinsiae (Leight.) A. Massal. (3), E. zonata (Körb.) Källsten ex Torrente & Egea (2), Erythrodecton granulatum (Mont.) G. Thor (1), Mazosia bambusae (Vain.) R. Sant. (1), M. aff. melanophthalma (Müll. Arg.) R. Sant. (2 different species; 2), and Neosergipea aurata (1). Based on previously published phylogenies (Ertz & Tehler Reference Ertz and Tehler2011; Aptroot et al. Reference Aptroot, Ertz, Lima, Jesus, Maia and Cáceres2013; Frisch et al. Reference Frisch, Thor, Ertz and Grube2014; Ertz et al. Reference Ertz, Tehler, Irestedt, Frisch, Thor and van den Boom2015), the clade including Chiodecton natalense Nyl. (2 sequences) and C. sorediatum G. Thor (1) was used as outgroup (see Fig. 1 for GenBank accession numbers). Only taxa for which the mtSSU sequence was available were used as this was the sole locus which had been sequenced for Neosergipea aurata, and consequently our analysis was performed on this locus.
Fig. 1 Maximum likelihood phylogenetic tree of the Enterographa clade using the small subunit mitochondrial rDNA sequences in RAxML 8.20. GenBank accession numbers are indicated for each OTU (Operational Taxonomic Unit) and bootstrap support values >70 are given below thickened branches. Chiodecton natalense and C. sorediatum used as outgroups. In colour online.
The 21 sequences were automatically aligned using MAFFT 7.244 (Katoh et al. Reference Katoh, Asimenos and Toh2009). After manual inspection and adjustment of obvious alignment errors, retaining the complete alignment of 825 bases, they were subjected to a maximum likelihood tree search using RAxML 8.20 (Stamatakis Reference Stamatakis2014), with the universal GTR-Gamma model and 500 non-parametric bootstrap pseudoreplicates. Trees were visualized in FigTree v1.4.2 (Rambaut Reference Rambaut2014) and further edited in Adobe Photoshop CS2 and Microsoft PowerPoint 2013.
Results
Nomenclatural novelties
Neosergipea M. Cáceres, Ertz & Aptroot nom. nov.
MycoBank No.: MB816075
Sergipea M. Cáceres et al. in Aptroot et al., Lichenologist 45: 629 (2013); type: Sergipea aurata M. Cáceres et al. (holotype).
Neosergipea aurata (M. Cáceres, Ertz & Aptroot) Lücking, M. Gut. & Moncada comb. nov.
MycoBank No: MB816076
Sergipea aurata M. Cáceres et al. in Aptroot et al., Lichenologist 45: 629 (2013); type: Brazil, Sergipe, Areia Branca, Fonte da Bicam, 2012, Cáceres & Jesus 12539 (ISE!—holotype).
Phylogenetic analysis
In our updated analysis, including for the first time all available mtSSU sequence data for this clade, Mazosia comes out as supported sister to a clade including the remaining species, in which Enterographa is supported sister to a clade including Erythrodecton, Neosergipea, and Dichosporidium (Fig. 1). The relationships between the three latter genera are resolved, albeit without support, with Erythrodecton basal in the clade and Neosergipea sister to Dichosporidium. The three sequenced species of Dichosporidium appear in two clades, both forming long branches (compared to the shared stem branch), suggesting that this genus might include two distinct entities (genera or subgenera), one with D. nigrocinctum and the other with D. boschianum and D. brunnthaleri.
Discussion
The discovery that the name Sergipea M. Cáceres et al. represents a later homonym is somewhat surprising, given that there has not been much activity in describing new plant, fungal and algal taxa in this area of north-eastern Brazil. Unfortunately, the earlier name Sergipea Regali et al., although governed by the same Code (McNeill et al. Reference McNeill, Barrie, Buck, Demoulin, Greuter, Hawksworth, Herendeen, Knapp, Marhold and Prado2012), does not appear in databases of plant names, and the only available sources are the Paleobiology Database (https://paleobiodb.org) and its recent successor, Fossilworks (http://fossilworks.org (Behrensmeyer & Turner Reference Behrensmeyer and Turner2013)), as well as the Paleobotany Database, maintained by the Borissiak Paleontological Institute of the Russian Academy of Sciences in Moscow (http://paleobotany.ru). However, while the latter is incomplete and does not include all names published in Sergipea sensu Regali et al. (Reference Regali, Uesugui and Santos1974), the first two contain factual and linking errors. Thus the author for the species Sergipea agadirensis is given as Deaf et al. (Reference Deaf, Harding and Marshall2014) in both the Paleobiology Database and Fossilworks (accessed 19 January 2016; Fig. 2), whereas it should correctly be Bettar & Meon (Reference Bettar and Meon2006); Deaf et al. (Reference Deaf, Harding and Marshall2014) do not mention the genus Sergipea. Also, links to supposed literature references do not work correctly. As a consequence, obtaining original information about the publication of Sergipea sensu Regali et al. (Reference Regali, Uesugui and Santos1974) and its included species was not straightforward.
Fig. 2 Entry for Sergipea agadirensis in the Fossilworks database (accessed 19 January 2016), with incorrect taxon author.
It is further unclear whether the fossil pollen described under the name Sergipea in fact represents pollen or dinoflagellate cysts (both governed under the Code); the name is treated as either in several recent publications, without clarification (Carvalho Reference Carvalho2004; Fensome & Williams Reference Fensome and Williams2004; Heimhofer & Hochuli Reference Heimhofer and Hochuli2010; Arai et al. Reference Arai, Lana and Ferreira2013). Also, a marine fossil mollusc was described from Brazil by Maury (Reference Maury1925) with the name Sergipia but elsewhere in the same work misspelled as Sergipea (http://www.gbif.org/species/4592627); while this name is not governed by the Code, it might cause additional confusion.
Instead of providing a replacement name for Sergipea M. Cáceres et al., a conservation proposal would be an alternative, although this would have very little chance of success since the name Sergipea sensu Regali et al. (Reference Regali, Uesugui and Santos1974) has received ample consideration after its publication, whereas Sergipea sensu Aptroot et al. (Reference Aptroot, Ertz, Lima, Jesus, Maia and Cáceres2013) is recent and has not been used except in its original publication. The fact that the names represent organisms in different kingdoms would in itself not prevent a successful proposal; some similar examples of conserved later homonyms between fungi and plants already exist in the Code.
Our updated phylogeny confirms that Neosergipea is firmly settled within the Enterographa clade and clusters with other genera that mostly feature pseudostromatic ascomata, including Enterographa crassa, whereas the basal sister clade, Mazosia, has ascomata resembling apothecia, with a peculiar, three-layered margin (Santesson Reference Santesson1952; Lücking Reference Lücking2008). However, the single locus used here (mtSSU) is apparently not sufficient to provide support within the subclade containing the genera Dichosporidium, Erythrodecton, and Neosergipea (see also Aptroot et al. Reference Aptroot, Ertz, Lima, Jesus, Maia and Cáceres2013), and additional loci such as the nuclear large subunit rDNA and the RPB2 gene (Ertz & Tehler Reference Ertz and Tehler2011; Frisch et al. Reference Frisch, Thor, Ertz and Grube2014; Ertz et al. Reference Ertz, Tehler, Irestedt, Frisch, Thor and van den Boom2015) are needed to establish sister group relationships in this lineage. Using the latter two loci, Ertz et al. (Reference Ertz, Tehler, Irestedt, Frisch, Thor and van den Boom2015) found an overall similar topology for this clade with good support throughout, including for the sister group relationship of Enterographa with Dichosporidium plus Erythrodecton; however, Neosergipea was not included owing to the lack of sequences for these two loci.
The separation of Dichosporidium into two supported clades on comparatively long branches, where the basal branch leading to these species is short and unsupported, was not previously recognized owing to smaller taxon sampling in this genus (Aptroot et al. Reference Aptroot, Ertz, Lima, Jesus, Maia and Cáceres2013; Frisch et al. Reference Frisch, Thor, Ertz and Grube2014); however, the recent study using the nuclear large subunit rDNA and the RPB2 gene found a similar topology (Ertz et al. Reference Ertz, Tehler, Irestedt, Frisch, Thor and van den Boom2015). A possible separation into two entities (genera or subgenera) seems to be supported by the fact that Dichosporidium nigrocinctum produces biclavate ascospores, whereas in D. boschianum and D. brunnthaleri they are hooked; also the associated photobionts have a different morphology (Thor Reference Thor1990). Chemically these species are similar, all containing protocetraric acid as the major compound (Thor Reference Thor1990). If this genus is split up in the future, the name Dichosporidium should be retained for the D. nigrocinctum clade since the type, D. glomeratum (Pat.) Pat., is a synonym of D. nigrocinctum (Thor Reference Thor1990).
We thank Fred R. Barrie (Field Museum, Chicago) for nomenclatural advice and Harrie J. M. Sipman (Botanical Garden and Botanical Museum, Berlin) for assistance with the literature search.
