Acrodiscus vidovichii (Menegh.) Zanardini

Manghisi, Antonio, Gall, Line Le, Bonillo, Céline, Gargiulo, Gaetano M., Ribeira, M. Antonia & Morabito, Marina, 2017, An assessment of the taxonomic status of the Mediterranean endemic genus Acrodiscus Zanardini (Halymeniales, Rhodophyta), European Journal of Taxonomy 267, pp. 1-24 : 10-17

publication ID	https://doi.org/ 10.5852/ejt.2017.267
DOI	https://doi.org/10.5281/zenodo.3844355
persistent identifier	https://treatment.plazi.org/id/03CA1827-FB34-A618-8226-FDA0FC3FFAB2
treatment provided by	Carolina
scientific name	Acrodiscus vidovichii (Menegh.) Zanardini
status

Treatment

Figs 1–7 View Fig View Fig View Fig View Fig View Fig View Fig View Fig ; Tables 1–2 View Table 1 View Table 2

Memorie del Reale Istituto Veneto di Scienze, Lettere ed Arti 14: 201 (1868). – Chondrus View in CoL ? vidovichii Menegh. in Savi, Sezione di Botanica , e Fisiologia Vegetabile, Adunanza del dì 16 Settembre 1841. In: Atti della terza Riunione degli Scienziati Italiani tenuta in Firenze: 427 (1841). – Cryptonemia vidovichii (Meneghini) Zanardini, Saggio di classificazione naturale delle Ficee: 42 (1843). – Euhymenia dichotoma (J.Agardh) Kütz. var. vidovichii Menegh. ex Kütz., Tabulae phycologicae; oder, Abbildungen der Tange. Vol. 17: 22, tab. 72 (1867). – Lectotype (designated here): Dalmatia [Šibenik, Croatia], Jul. 1841, Vidovich folder 742.4, n.11, fragments at the top and at the bottom left (PI!) ( Fig. 7 View Fig ).

Cryptonemia dichotoma J.Agardh , Algae maris Mediterranei et Adriatici: 100 (1842). – Cryptonemia View in CoL (section Acrodiscus View in CoL ) dichotoma J.Agardh , Species genera et ordines algarum: 225 (1851). – Euhymenia dichotoma (J.Agardh) Kütz. , Species algarum: 742 (1849). – Type: France, Nice, near St. Hospice, 1841, J. Agardh s.n. (LD, BM!, BM000619430, PC!, PC0523534).

Acrodiscus vidovichii Zanardini f. cochlearis Erceg., Acta Adriatica IV: 76 (1949). syn. nov. – Type: Adriatic, Croatia.

Description

Thalli up to 10 cm in length, the blade segments typically 1–3 cm long by (4–)7(–10) mm broad by 200–250 µm thick ( Fig. 1 View Fig ), compressed to flattened, thin, membranous-fleshy, dark red in color, erect from a very short cuneate stipe with a discoid holdfast, the blades subdichotomously branched, linear and slightly channeled, the apices broadly rounded ( Figs 1 View Fig C–D, 2A, 3A). Constrictions occasional between forks ( Fig. 1D View Fig ) and especially at sites of branching ( Fig. 1B, D View Fig ); proliferous blades frequent at constrictions ( Fig. 1B View Fig ) or from lower stipes ( Fig. 1 View Fig B–D).

Fronds multiaxial ( Fig. 2A View Fig ), the cortex anticlinal ( Fig. 2 View Fig A–B), the medulla densely filamentous ( Fig. 2D View Fig ); cortical filaments 5- or 6-layered, pseudo-dichotomously branched, the cells subspherical to ellipsoid ( Fig. 2B View Fig ), progressively smaller outwardly, 5–9 µm in diameter proximally, 2–3 µm in diameter at surface ( Fig. 2B View Fig ) and evenly spaced or slightly paired ( Fig. 2C View Fig ). Subsurface cortical cells secondarily pit-connected; short longitudinal multicellular ‘bridges’ sometimes linking adjacent cortical cells or growing into the medulla from the transition zone between cortex and medulla; stellate (“ganglionic” sensu Womersley & Lewis 1994) and refractive medullary cells or filaments absent. Medulla occupying half of the blade sections, composed of interwoven longitudinal or, less commonly, oblique and transverse filaments ca 5 µm in diameter ( Fig. 2D View Fig ).

Female and male reproductive structures not observed. Tetrasporangia developing in eliptical nemathecia located subapically ( Fig. 3A View Fig ). Tetrasporangial filaments usually three-celled, the terminal cell a cruciate/ decussate-cruciate tetrad (30–)33(–35) µm long by 12–15 µm wide ( Fig. 3 View Fig C–D); subapical cells ellipsoid, bearing two simple or once-dichomous sterile filaments that surround the sporangia ( Fig. 3C View Fig ); basal

cells deltoid, sterile nemathecial paraphyses four-celled ( Fig. 3C View Fig ), the proximal cells narrowly falcate, the terminal cells smaller in diameter and subspherical ( Fig. 3C View Fig ).

Distribution and habitat

Acrodiscus is uncommon but widely distributed across the Mediterranean Sea ( Fig. 4 View Fig ; see also Guiry & Guiry 2016; Manghisi et al. 2010a); it is a sciaphilous species, found throughout the year on rocky substrata from depths of 0– 50 m. Tetrasporophytes were collected in spring and autumn ( Table 1 View Table 1 ).

Taxonomic history

In the year following Meneghini’s ( Savi 1841) proposal of Chondrus ? vidovichii from Dalmatia [collected by Vidovich, fide Zanardini (1868)], J. Agardh (1842) described Cryptonemia dichotoma from collections near Nice. Zanardini (1843) soon after regarded Chondrus ? vidovichii and Cryptonemia dichotoma as conspecific and a true member of Cryptonemia , creating Cryptonemia vidovichii based on Meneghini’s prior naming. Apparently disregarding Zanardini’s (1843) proposals, Kützing (1849) transferred C. dichotoma to his own new genus Euhymenia , which is now regarded as synonymous with Kallymenia ( Guiry & Guiry 2016) . Next, J. Agardh (1851), ignoring Kützing’s Euhymenia , put Cryptonemia vidovichii into his newly proposed section Acrodiscus of Cryptonemia , along with Phyllophora crenulata J.Agardh and C. denticulata J.Agardh , on the base of their morphology and the presence of subapical tetrasorangial sori. Kützing (1867) then made Meneghini’s species a variety of J. Agardh’s Cryptonemia dichotoma , thus not acknowledging the synonymy of the two as had been advocated by Zanardini (1843). Soon afterwards, Zanardini (1868) removed Cryptonemia vidovichii (which he still regarded as synonymous with C. dichotoma ) from the genus Cryptonemia and placed it into a newly created one, Acrodiscus , named after the section made by J. Agardh. De Toni (1905) transferred J. Agardh’s C. crenulata and C. denticulata to Acrodiscus (as A. crenulatus (J.Agardh) De Toni and A. denticulatus (J.Agardh) De Toni ), although both are currently regarded as genuine species of Cryptonemia ( Guiry & Guiry 2016) .

In 1949, Ercegović proposed Acrodiscus vidovichii f. cochlearis, arguing that the specimens from Dalmatia ( Croatia) had “spoon-shaped”, rather than the flattened fronds described by several other workers ( Ardissone 1883; Hauck 1885; Preda 1908; Zanardini 1868). Ercegović overlooked, however, the fact that populations from throughout the Mediterranean had been described as both compressed-flat or plane ( Ardissone 1883; Hauck 1885; Kylin 1956; Savi 1841; Preda 1908; Zanardini 1868) and with bent/curved sub-grooved margins ( Agardh 1842; Aleem 1993; De Toni 1905; Feldmann 1939). In our experience, freshly collected specimens normally have bent/curved margins but flatten once pressed on herbarium sheets; younger and thinner specimens, on the other hand, can be planar throughout and usually adhere to paper, whereas older, more coriaceous specimens may remain canaliculate and nonadherent. We therefore find little reason to recognize a separate forma cochlearis.

Lectotypification

Chondrus ? vidovichii Menegh. was validly published in what is commonly reported as Menghini’s Algologia Dalmatica ( Guiry & Guiry 2016) in Atti della terza Riunione degli Scienziati italiani tenuta in Firenze nel Settembre 1841 ( Savi 1841). Indeed, the latter is a congress acta in the form of a book with various sections. During the meeting of the Botany and Plant Physiology group, Meneghini showed his manuscript to the assembly. The secretary of the group, Pietro Savi, recorded the meeting events in the acta, and transcribed part of Meneghini’s manuscript, reportedly titled Algologia Dalmatica, including its novelties. With specific reference to Chondrus ? vidovichii, Savi copied the Latin diagnosis and noted the lack of reproductive structures, and made reference to an illustration that does not appear in the acta. No holotype is designated, nor is there an iconotype that might serve as one.

In the Library of Natural and Environmental Sciences of the University of Pisa, Italy, we found numerous manuscript documents belonging to Meneghini, among them the original complete manuscript of the so-called Algologia Dalmatica, actually Alghe Dalmate, enumerate ed illustrate dal professor Giuseppe Meneghini ( Fig. 5 View Fig A–B), along with plates including his illustration of Chondrus ? vidovichii ( Fig 6 View Fig ). Unfortunately, the manuscript was never published.

Interestingly, in other documents there is evidence that: a) Meneghini received material from Dalmatia ( Croatia) collected either by Vidovich in Sebenico (Šibenik), by Sandri in Zara (Zadar), or by Stalio in Spalato (Split); b) Menegnini received material from Vidovich in July 1841 (including a Chondrus ?); and c) Meneghini dedicated to Vidovich all the new species collected by him. Consequently, it can be inferred that the type material should have been collected by Vidovich in Sebenico in July 1841.

Finally, we found that the Herbarium Horti Botanici Pisani (PI) holds a number of Meneghini specimens. In a folder labelled “ 742. 4. Euhymenia dichotoma Kg. ” is an envelope and three sheets numbered “11”. The envelope contains ten specimens of A. vidovichii , three of them on numbered sheets (224, 778, 783). Two of the three sheets (upper and lower left) each have a fragment of the specimen drawn in the abovementioned plate ( Fig. 7 View Fig ). Consequently, we designate as type material of Chondrus ? vidovichii

Meneghini the two fragments on two of the “11” sheets that were portions of the single specimen he illustrated in the unpublished figure accompanying his manuscript.

Phylogenetic analyses

The DNA barcode region was generated for 15 samples from different Mediterranean localities, including the type area; the sequences are now lodged in BOLD and Genbank ( Table 1 View Table 1 ). Divergence among generated sequences ranged from 0–3 bp (0–0.53%), which is a typical level of within-species variation.

Phylogenetic analyses inferred from both rbc L and LSU markers ( Fig. 8 View Fig and trees not shown) resolved three strongly supported supergeneric lineages within the Halymeniales : a) one of A. nitidissima J.Agardh and species of Pachymenia J.Agardh ; b) a second comprised of Polyopes J.Agardh and Glaphyrosiphon intestinalis (Harv.) Leister & W.A.Nelson ; and c) a third consisting of Grateloupia C.Agardh , Yonagunia Kawag. & Masuda , Pachymeniopsis Yamada ex Kawab. , Prionitis J.Agardh , Phyllymenia J.Agardh , Mariaramirezia M.S.Calderon, G.H.Boo, A.Mansilla & S.M.Boo , Kintokiocolax Tak.Tanaka & Nozawa and Dermocorynus P.Crouan & H.Crouan. The relationships among the remaining halymeniacean genera included in our analyses were poorly or not resolved. Cryptonemia J.Agardh was polyphyletic and Thamnoclonium Kützing was paraphyletic in rbc L analyses, and the genus Halymenia C.Agardh was polyphyletic in both rbc L and LSU trees.

The exact alliance of Acrodiscus was uncertain, as it varied depending on the phylogenetic reconstruction methods and the marker. In rbc L analyses, A. vidovichii was included in an unsupported lineage encompassing Felicinia marginata (Roussel) Manghisi, L.Le Gall, Ribera, Gargiulo & Morabito and Corynomorpha prismatica (J.Agardh) J.Agardh. This assemblage in turn grouped with particular, especially type, species of Halymenia , Cryptonemia , Carpopeltis F.Schmitz , Codiophyllum J.E.Gray , Spongophloea Huisman, De Clerck , Prud’homme & Borow., Thamnoclonium Kütz. , Epiphloea J.Agardh and Gelinaria Sond. In LSU trees, Acrodiscus grouped with Corynomorpha and species of Pachymeniopsis , Dermocorynus , Grateloupia and Prionitis . In concatenate LSU- rbc L analyses ( Fig. 8 View Fig ), it was sister to Corynomorpha with variable degrees of support, both genera being included in a deeper lineage encompassing Felicinia Manghisi, L.Le Gall, Ribera, Gargiulo & Morabito, Halymenia , Cryptonemia , Gelinaria , Epiphloea and Isabbottia M.S.Balakr.