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Article

Hoefkenia hunsrueckensis, a New Genus and Species from Europe, and the Identity of Virescentia vogesiaca (F.W.Schultz ex Skuja) Necchi, D.C.Agostinho & M.L.Vis (Batrachospermales, Rhodophyta)

by
Eberhard Fischer
1,*,
Dorothee Killmann
1,
Johanna Gerlach
2,
Claudia Schütte
2,
Burkhard Leh
1,
Kai Müller
3 and
Dietmar Quandt
2
1
Institute for Integrated Natural Sciences—Biology, University of Koblenz, Universitätsstraße 1, 56070 Koblenz, Germany
2
Bonner Institut für Organismische Biologie—Abt. I. Biodiversität der Pflanzen, Universty of Bonn, Meckenheimer Allee 170, 53115 Bonn, Germany
3
Institute for Evolution and Biodiversity, University of Münster, Hüfferstr. 1, 48149 Muenster, Germany
*
Author to whom correspondence should be addressed.
Diversity 2024, 16(8), 473; https://doi.org/10.3390/d16080473 (registering DOI)
Submission received: 20 June 2024 / Revised: 29 July 2024 / Accepted: 2 August 2024 / Published: 5 August 2024
(This article belongs to the Special Issue Freshwater Biodiversity Hotspots in 2024)
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Abstract

:
Freshwater red algae from Hunsrück-Hochwald National Park previously identified as Virescentia vogesiaca are described as Hoefkenia hunsrueckensis gen. et sp. nov. They cluster in the phylogenetic tree together with Kumanoa and form its sister clade. Virescentia is rendered monophyletic by exclusion of these samples. The taxonomic history of Virescentia vogesiaca is described. The species was named by Skuja referring to the description of Batrachospermum vagum var. flagelliforme Sirodot and the specimens all come from Western France and Spain. The name Batrachospermum vogesiacum was erroneously applied referring to a specimen from the North Vosges close to Germany collected and annotated by F.W. Schultz and representing the new Hoefkenia hunsrueckensis. However, this specimen was never cited in the protologue of Virescentia vogesiaca. We provide evidence that the real Virescentia vogesiaca is endemic to Western France and Spain, and that Hoefkenia hunsrueckensis is restricted to Eastern Belgium, Eastern France and SW Germany, differing in morphological and molecular characters.

1. Introduction

The freshwater red algae have received attention in the last 20 years partly as they are important bioindicators for water quality and are useful in the ecological assessment of rivers and streams, but also due to an international cohort of taxonomists who have for the last three decades been trying to unravel the complex taxonomy of particularly the Batrachospermales. In Europe, new identification guides have been published in recent years (e.g., [1,2]) and mapping of these often endangered plants has been intensified (e.g., [3,4,5]). However, knowledge in many parts of Europe is still scarce, and in many areas (e.g., parts of Germany) [6], more efforts need to be made to understand their ecology and conservation status. Here, we report on the discovery of a new genus and species resembling Virescentia vogesiaca (Skuja) Necchi et al. [7] (Batrachospermum vogesiacum Skuja [8]) at first glance, made during the assessment of freshwater red algae in the Hunsrück-Hochwald National Park in Western Germany as part of the German Barcode of Life Initiative (GBoL).
The genus Batrachospermum Roth [9] with the type species B. gelatinosum (L.) DC. [10] (Conferva gelatinosa Linnaeus [11]) was considered the most species-rich genus of freshwater red algae with c. 112 species recognized [12]. However, this genus has been shown to be paraphyletic in phylogenetic studies based on molecular data [13]. It has been divided into several genera: Kumanoa Entwisle et al. [13,14], Sheathia Salomaki et al. [15], Nocturama Entwisle et al. [16], Nothocladus Skuja [17], now enlarged to comprise most of the old informal “Australasica-group” [16], Torularia Bonnemaison [18] (Setacea Necchi & Rossignolo [19]), Atrophycus Rossignolo et al. [20], Wynne [21], Acarposporophycos Necchi et al. [22], Visia Necchi et al. [22], Volatus Chapuis et al. [23] with three species from North America and Europe, Lympha Evans et al. [24], Virescentia Necchi et al. [7], Montagnia Necchi et al. [25], Ahidranoa Fischer et al. [26], and Paludicola Vis et al. [27]. Thus, the genus Batrachospermum s.str. comprises now only Batrachospermum gelatinosum (L.) DC. with few related species. For an overview of the taxonomy of Batrachospermaceae, see [26].
The genus Virescentia comprises species with greenish thalli, well developed whorls, carposporophytes produced singly or in pairs along the main axis, straight carpogonial branches and typically cylindrical and stalked trichogynes [28]. While the morphological study of Sheath et al. [29] reduced the number of species within Virescentia, molecular data have suggested that there is a considerable genetic variation and that this variation is partitioned geographically [28,30].
Sirodot [31] described Batrachospermum vagum (Roth) C.Agardh [32] (Chara gelatinosa var vaga Roth [33]: var. c. flagelliforme) and listed in the protologue the following localities from France: “ruisseau du Moulin à papier, lande de Lambrun; ruisselets de Logerie-Haute, treillage de Beignon, forêt de Paimpont; de la lande de Beignon”. He states that this taxon occurs in streams and small streams in peat (“Ruisseaux et ruisselets en pleine tourbe”). The specimens were all collected in summer. Skuja [8], in a paper on the freshwater red algae from the German Limnological Expedition to the Sunda Islands, raises this variety to species level by using the herbarium name Batrachospermum vogesiacum, thus creating a nomen novum and referring to its valid description in [31]: “Die Sirodotsche var. flagelliforme muß dagegen als eine gut charakterisierte besondere normal fruchtende Art—Batrachospermum vogesiacum T.G.Schultz—renoviert werden” (the variety flagelliforme described by Sirodot, however, has to be renewed as a well characterized, normally fruiting species—Batrachospermum vogesiacum T.G.Schultz). This new name is based on a specimen housed in PC (acronyms after [34]) and annotated by the German Botanist Friedrich Wilhelm Schultz in his handwriting as Batrachospermum vogesiacum. It was distributed by Schultz as an exsiccatum in the series “Flora Galliae et Germaniae exsiccatae” as Nr. 594. Batrachospermum moniliforme Roth, cat. 2, p. 847; Wallr., Crypt. 1, p. 23; var. e viridis Bory, t. 30, f. 4; D. 979. 4 Avril 1840. “Sur les pierres de grès vosgien, dans le fond des ruisseaux limpides qui parcourent des prairies tourbeuses, près de Bitche”; dec. et rec. F.G.Schultz. Beside the annotation as “B. vogesiacum” by Schultz, there is an asterisk in pencil, and above the label, there is written “vide/H.S.”. Skuja has apparently seen this specimen and validated Schultz’s name after almost 100 years [8]. He has, however, never cited this specimen, nor was it cited in the protologue of Batrachospermum vagum var. flagelliforme by [31]. Friedrich Wilhelm Schultz (1804–1876) was a German botanist who, however, lived most of his life in adjacent France, mainly due to political reasons [35]. He abbreviated his first names in French, i.e., Frédéric (=Friedrich) Guillaume (=Wilhelm) Schultz. Skuja apparently misinterpreted the F. for Frédéric and created the abbreviation T.G. Schultz which was used by nearly all subsequent authors [7] and also in AlgaeBase [36]. The correct official abbreviation, however, is F.W.Schultz [37]. On the same sheet, there is also a specimen annotated as Batrachospermum vagum var. flagelliforme—fructifié, and, in pencil “Batrachospermum vogesiacum T.G.Schultz—det. H.Skuja”. On the backside of the sheet the locality for this plant is written: “Lande de Lambrun—1er août 1880.” In conclusion, the specimen 594 collected by Schultz in the North Vosges has never been cited in the protologue of Batrachospermum vagum var. flagelliforme nor by [8] when creating the nomen novum. Compère [38] thus correctly designated one of Sirodot’s specimens from Brittany in the environment of Rennes (Ruisselets de Logerie Haute, Sirodot s.n., 1er août 1880, PC) as lectotype for Batrachospermum vogesiacum. A duplicate of the specimen Schultz 594 is housed at BM.
In almost all recent publications, Batrachospermum vogesiacum is not cited for Germany. Israelson [39] listed five localities from South West Sweden, Compère [40] listed six localities from the Belgian-French Ardennes and the Haute Fagne, and [12] cites France and Belgium. Eloranta et al. [1,41] mention Belgium, France and Sweden. Also [7] in the revision of the genus Virescentia Necchi et al. listed only Belgium, France, Spain and Sweden [7]. Recently, the species was recorded for the first time for Central Finland in acid dystrophic rivers [3,4]. The first record of Batrachospermum vogesiacum for Germany was made by Fischer [42] in the Rotmurg stream in Northern Black Forest under the name of Batrachospermum vagum var. flagelliforme. However, this record soon fell into oblivion, and the species is not mentioned in the Red List of German Freshwater Red algae [43]. Schütz [44] listed this record as not confirmed since 1956, and no specimen was retrieved. The authors of [45] were the first to draw attention to this neglected taxon. During a mapping of freshwater red algae in Rhineland-Palatinate (Hunsrück, Palatinate) and Saarland, Peter Wolff could detect 18 localities, and the authors gave a first characterization of identification characters, distribution and ecology [45]. Subsequently, Batrachospermum vogesiacum was included in [2] who provided a flora of freshwater red algae for Germany and adjacent regions.
The first molecular data for Batrachospermum vogesiacum were published by Chiasson et al. [46] from two localities in South Western France (Aquitania). The authors showed that the species is distinct from Batrachospermum helminthosum. Necchi et al. [7] established the new genus Virescentia for the members of Batrachospermum section Virescentia Sirodot [47] and subsequently transferred Batrachospermum vogesiacum to this genus. They provided a thorough morphological and molecular revision and used the rbcL-sequences from France already published in Chiasson et al. [46], and from one locality in Spain.
The present authors collected “Virescentia vogesiaca” in the Hunsrück-Hochwald National Park in Western Germany and the Haute Fagne close to the German border. Molecular and morphological data, however, revealed that this taxon differs considerably from the true Virescentia vogesiaca. Therefore, the objective of this study is to characterize morphologically and molecularly an undescribed genus and species that is described below.

2. Materials and Methods

2.1. Sample Collections

Fresh water red algae were sampled between 2016 and 2018 from localities in Germany and Belgium. Herbarium vouchers with specimens preserved in 70% alcohol were deposited in BONN, BR, KOBL (abbreviations after [34], compare Table 1). The morphology was examined with a KEYENCE VHX-S15 Digital microscope, Neu-Isenburg, Germany. The microphotographs were made with the same digital microscope.

2.2. Phylogenetic Analyses

DNA isolation as well as amplification and sequencing of COI and rbcL followed [26]. Quality control of the pherograms, contig assembly and alignment was done in PhyDE1 (available at www.phyde.de, accessed on 1 March 2021). In order to place the taxon from the Hunsrück and the Haute Fagne in a phylogenetic context, a representative set of rbcL and COI sequences from freshwater red algae were downloaded from GenBank (Table 2) and aligned with the newly generated sequences using PhyDE1. Sampling was guided by [13,26].
Maximum likelihood (ML) analyses were performed using raxmlHPC-PTHREADS-SSE3 version 8.2.10 [48] via the raxmlGUI 2.0 [49] applying the GTR + Γ model and 1000 replicates for the bootstrap analysis.
Bayesian analyses were performed with MrBayes v.3.2.5 [50], applying the GTR + Γ + I model with model parameters unlinked across the two partitions COI and rbcL. Four runs with four chains (10 mio. generations each) were run simultaneously, using default settings for the MCMC sampler and sampling a chain every 1000 generations. Tracer v.1.7.1 [51] was used to examine the stationarity of the chains; convergence of parameter values was assessed via the potential scale reduction factor and effective sampling size. The consensus tree and posterior clade credibility values were computed using a burn-in of 25%. Consensus topologies and support values were compiled and drawn using TreeGraph v.2 [52]. Bayes factors were used to compare alternative topological hypotheses, and the significance of differences was evaluated according to Kass & Raftery [53]. Specifically, the ratio of the marginal likelihoods was estimated for three pairs of analyses in which hard and corresponding negative monophyly constraints were enforced, respectively. The harmonic mean of the likelihood values from the MCMC samples under a given hypothesis was used to estimate the marginal likelihood of this model (see below under Results for the precise hypotheses tested).

3. Results

3.1. Phylogenetic Analyses

The concatenated, aligned data set comprised 1943 characters (rbcL: 1280; COI: 663) for 34 taxa (compare Table 1 and Table 2). Phylogenetic inferences resulted in a well resolved and well supported phylogeny of the Batrachospermales (Figure 1). In particular, two large sister clades were resolved with strong support: one containing Kumanoa, Virescentia, Visia, and Paludicola turfosa (Bory) Necchi & Vis [27] (=Batrachospermum turfosum Bory [54]), the other Batrachospermum s.str., Tuomeya Harvey [55], Sirodotia Kylin [56], Lemanea Bory [57], Sheathia, Nothocladus, and Nocturama. Within the first clade, Kumanoa including K. globospora (Israelson) Entwisle et al. [13] (Batrachospermum globosporum Israelson [39]), occurring in Sweden, and K. virgatodecaisneana (Sirodot) Entwisle et al. [13] (Batrachospermum virgatodecaisneum Sirodot [31]), occurring in France, Sweden and Latvia, and the new Hoefkenia hunsrueckensis are joint in a maximally supported subclade. Another subclade unites Virescentia vogesiaca s.str., V. helminthosa (Bory) Necchi et al. [7] (Batrachospermum helminthosum Bory [54]), V. viride-americana Necchi et al. [7], and V. viride-brasiliensis (Necchi & Agostinho) Necchi et al. [7] (Batrachospermum viride-brasiliensis Necchi & Agostinho [28]). Phylogenetic signal is insufficient to clearly resolve the phylogenetic relationships between these two subclades and relative to Visia cayennensis (Montagne ex Kützing) Necchi & A.Garcia [22] (Batrachospermum cayennense Montagne ex Kützing [58]).
A fourth subclade within this first clade contains the samples from Batrachospermum turfosum, again confirming clear independence of this species from Batrachospermum gelatinosum. The Batrachospermum turfosum group has recently been placed into the new genus Paludicola [27].
In view of this somewhat lacking internal clarity in the first major clade, we explicitly tested support in the data for three pairs of alternative topological hypotheses. Specifically, we tested whether “V. vogesiaca” from Hunsrück is more closely related to V. vogesiaca from other locations than to any other species; i.e., whether there was any support in the data for “V. vogesiaca” from Hunsrück and the other V. vogesiaca samples together possibly forming a monophyletic group, which would be in agreement with simply assigning the Hunsrück samples to V. vogesiaca. There was very strong evidence (using terminology of Kass & Raftery [53]) against this scenario (harmonic mean of log likelihoods −18,145.11; which is about 53 log units less likely than the alternative scenario in which “V. vogesiaca” from Hunsrück and the other V. vogesiaca do not form a monophyletic group (harmonic mean of log likelihoods −18,092.43)).
The second test compared the hypothesis of a monophyletic genus Virescentia (including the Hunsrück samples of “Virescentia vogesiaca”, the other samples of Virescentia vogesiaca from other locations, plus Virescentia helminthosa, Virescentia viride-americana and Virescentia viride-brasiliensis) against a non-monophyletic one. There was very strong evidence against the first hypothesis (harmonic mean of log likelihoods −18,155.60; about 58 log units worse than the alternative one in which Virescentia was non-monophyletic (harmonic mean of log likelihoods −18,097.29).

3.2. Taxonomic Treatment

Hoefkenia Eb.Fisch., Killmann, Leh, K.Müll. & D.Quandt, gen. nov.
Diagnosis: The genus shares with Paludicola, Virescentia and Kumanoa the axial-central carposporophyte forming a hemispherical or spherical structure and usually only 1 (−2) per whorl, and a usually well-developed whorl. It differs from Kumanoa, with which it clusters in the phylogenetic tree, in the straight carpogonial branches (curved or twisted in Kumanoa). It differs from Paludicola in the carposporophyte with gonimoblast filaments that show only one type (two types of gonimoblast filaments in Paludicola, i.e., radially branched determinate filaments with carpogonia at the tips, and prostrate indeterminate filaments). It differs from Virescentia in the unique rbcL- and COI-sequences clustering with Kumanoa and the unstalked or only very shortly stalked club-shaped trichogyne (see Table 3).
Type: Hoefkenia hunsrueckensis Eb.Fisch., Killmann, Leh, K.Müll. & D.Quandt sp. nov.
Etymology: The genus is named after Ulrike Höfken, former Minister of Environment, Energy, Nutrition and Forests of the Federal State of Rhineland-Palatinate for her initiative to gazette Hunsrück-Hochwald National Park as the first National Park of Rhineland-Palatinate in 2015, and for her continuous and enthusiastic support of this Park.
Hoefkenia hunsrueckensis Eb.Fisch., Killmann, Leh, K.Müll. & D.Quandt sp. nov. (Figure 2 and Figure 3).
Type: Germany. Rhineland-Palatinate, Hunsrück Hochwald National Park, Thranenbach at parking place Thranenweiher, 49°42′33.26″ N 7°6′08.44″ S, alt. 583 m, 10 August 2017, E.Fischer, B.Leh & D.Killmann 435/2017 (holotype B!, isotypes: BR, KOBL).
Diagnosis: The species resembles superficially Virescentia vogesiaca but differs in the unstalked or only shortly stalked and larger trichogyne, stalk 0–3 µm vs. 5–10 µm in V. vogesiaca, carpogonium 34–48 µm length vs. 20–45 µm in V. vogesiaca. In addition to the unique rbcL sequences, both taxa have a disjunct geographic pattern that can be applied as an additional criterion.
Thalli moderately mucilaginous, grey-green to olive-brown or yellow-green, richly branched, branching irregular, branches flagelliform, often with shorter or longer hairs at the end of primary fascicles, 3–14 cm high, whorls contiguous or separated, barrel-shaped, obconical to cylindrical, 305–559 µm wide. Primary fascicles with 6–9 cell storeys. Secondary fascicles sparse, shorter than primary fascicles.
Monoecious. Spermatangia spherical, on primary or secondary fascicles, 8–9 µm wide. Carpogonial branches straight, 50–73 µm long, involucral filaments short. Carpogonia 34–48 µm long, with almost sessile or shortly stalked trichogyne, stalk 0–2.5 (–3) µm long, trichogyne club-shaped, 8–9 µm wide, usually widest at apex. Carposporophyte globose, 55–95 µm in diameter. Carposporangia obovoid, 8–9 × 6–7 µm.
Etymology: The species is named after the Hunsrück-Hochwald National Park, where 16 out of 25 known localities (64%) are situated. Germany and its Federal States Rhineland-Palatinate and Saarland have thus a special responsibility for the conservation of this new species.
Ecology and distribution: Hoefkenia hunsrueckensis occurs in small acidic streams in the Hunsrück-Hochwald National Park in Germany, in the Haute Fagne in Belgium close to the German border and in the Vosges (Wasgau) close to Germany. It is found in acidic streams between 530 and 648 m a.s.l. The new Hoefkenia hunsrueckensis is abundant in the springs and rivers originating on the quartzitic ridge, usually accompanied by bryophytes: Scapania undulata (L.) Dumort., Sphagnum auriculatum Schimp., Pellia epiphylla (L.) Corda, Racomitrium aciculare (Hedw.) Brid. or Marsupella emarginata (Ehrh.) Dumort. Accompanying vascular plants are Juncus kochii F.W.Schultz or Potamogeton polygonifolius Pourret. Rarely, few other red algae like Batrachospermum gelatinosum or Sheathia confusa (Bory) Salomaki & M.L.Vis [15] (Batrachospermum ludibundum Bory [54] var. confusum Bory [54]) occur. The water temperature in the springs and streams of the Hunsrück varies between 3 °C to 18.3 °C in summer with average of 5 °C to 6 °C. The pH varies between 4.5 and 5.9. For detailed vegetation relevés see Knappe & Wolff [45]. Interestingly, Hoefkenia hunsrueckensis can be observed in almost every month of the year. Recently, an endemic lichen (Verrucaria hunsrueckensis Thüs et al. [59]) has been described from this area.
Apart from the Hunsrück area, there are several localities of Hoefkenia hunsrueckensis mentioned in the literature under the name of Batrachospermum vogesiacum: five localities in Eastern Belgium in the Haute Fagne (mainly the spring region of the Rur, see [40]), four localities in the Palatinate Forest on sandstone rocks [45], and two localities in the Wasgau with one in the Southern Palatinate close to the French border and one east of Bitche where Schultz collected the first specimen [45]. However, specimens from most of these localities were not available for study. We could confirm localities in the Haute-Fagnes and in the Hunsrück. A careful search in 2018 at Schultze’s locality near Bitche did not reveal any specimen. Search in the Haute-Fagnes showed that at least one locality bears populations of Paludicola turfosa, a taxon not mentioned by [40] and probably confused with the new Hoefkenia. Thus, here we only cite the confirmed records, and it is evident that Hoefkenia hunsrueckensis has its main distribution in the Hunsrück-Hochwald National Park. The algae from Sweden and Finland, originally identified as Virescentia vogesiaca, were not available for molecular study and may well represent another undescribed taxon. A similar case was reported with Paludicola groenbladii M.L.Vis, Necchi & P.Eloranta from Finland and Poland [27], a new species originally identified as Batrachospermum vagum (Roth) C.Agardh (=Paludicola turfosa).
Additional specimens examined (paratypes): Belgium. Rur near Grünkloster, 50°29′38.55″ N 6°10′20.32″ E, 527 m, 22 April 2017, Fischer, Gerlach & Quandt RA05 (KOBL).
Germany. Rhineland-Palatinate, Hunsrück-Hochwald National Park,
Thranenbruch 49°43′15.57″ N 7°6′54.70″ E, 648 m, 11 May 2017 (KOBL); Ochsenfloß NW of Börfink, 49°41′20.51″ N 7°4′20.08″ E, 551 m, 11 May 2017, Fischer, Killmann & Leh s.n. (KOBL).
France. “Sur les pierres de grès vosgien, dans le fond des ruisseaux limpides qui parcourent des prairies tourbeuses, près de Bitche”, 49°02′12.11″ N 7°31′40.31″ E, 4 April 1840, F.G.Schultz 594.(PC, BM).
Virescentia vogesiaca (F.W.Schultz ex Skuja) Necchi, D.C.Agostinho & M.L.Vis
Type: France. Brittany in the environment of Rennes, Ruisselets de Logerie Haute, Sirodot s.n., 1er août 1880, 47°58′58″ N 2°10′26″ W (lectotype PC0591499!, chosen by Compère 1991b); lande de Lambrun—1er août 1880, Sirodot s.n., 1880, 48°02′44.08″ N 2°13′55.59″ W (PC).

4. Discussion

As shown above (see Section 3), there is little evidence that the new taxon is part of Virescentia, as all analyses do not resolve a monophyletic Virescentia including the species from the Hunsrück. The analyses would place the new taxon into Kumanoa but there are no morphological characters to support this decision. The main distinguishing character of Kumanoa is the twisted or spirally coiled carpogonial branch while that of Virescentia and the new taxon is straight [7,13]. Table 3 gives an overview of the morphological differences between the new Hoefkenia and Kumanoa, Virescentia, Visia and Paludicola. It shows that the morphological differences are often not very marked.
The new taxon could be placed in Kumanoa according to the phylogenetic results. However, Kumanoa is one of the few genera with a distinct morphology, i.e., the curved or spirally coiled carpogonial branches. Placing the new taxon in Kumanoa would mean that we abandon an important autapomorphy of the latter genus. The combination of Kumanoa, Virescentia, Visia and eventually Paludicola into a single genus Kumanoa, which would have priority, would contradict all recent papers on systematics of Batrachospermales and this genus could not be sufficiently characterized by morphology. Our approach to place the taxon from Hunsrück into a new genus results in more nomenclatural stability. Otherwise, five taxa of Virescentia, four of Visia and 15 taxa of Paludicola would have to be combined under Kumanoa. Creating a paraphyletic genus Virescentia when describing the new taxon in this genus is, in our view, also not a very useful solution. For the differences between Hoefkenia, Kumanoa, Paludicola, Virescentia and Visia, see Table 3.
Thus, we argue for a new genus of its own, Hoefkenia gen. nov., sister to Kumanoa. Another yet unpublished study on German freshwater red algae that included a sample of “Virescentia vogesiaca” from the Thranenbach in Hunsrück-Hochwald comes to the same conclusion concerning the phylogenetic position of the taxon despite a different taxon sampling (T. Friedl pers. com., accessed on 12 February 2021). It is true that we do not have material from the lectotype locality of Virescentia vogesiaca near Rennes for molecular studies. We just examined the type and compared it with material collected in SW France cited by [46], which we found identical to typical V. vogesiaca. This opinion is confirmed by [7]. We agree that a careful search at the type locality should be performed to confirm our results with sequencing of typical V. vogesiaca. However, this was not possible up to now but should be done in the near future if the species is still present there. Entwisle [60] already could not find extant populations of Virescentia vogesiaca near Rennes.
Recent studies based on molecular and morphological evidence [7,28] revealed that Batrachospermum vogesiacum, B. helminthosum and B. sirodotii Skuja ex M.P.Reis [61] previously reported from Brazil [62] based on morphological characters represent a new taxon Virescentia viride-brasiliensis [7,28]. Thus, the report of Virescentia vogesiaca from South America, also mentioned by [2], is erroneous. All species of Virescentia are restricted to one single geographic area [7] and seemingly widespread species like Virescentia helminthosa have been divided into several specific units. The true Virescentia helminthosa is endemic to Western Europe while the North American taxon has been described as V. viride-americana, and the South American taxon as V. viride-brasiliensis [7]. The Japanese Virescentia helminthosa reported by [30] represents two probably undescribed species based on genetic data. Virescentia vogesiaca is apparently restricted to Western France and Spain, and the plants from Sweden and Finland need further study. Molecular data suggest that the Japanese plants [30] belong to at least another yet undescribed taxon. The morphological differences between the six Virescentia species are shown in Table 4 (see also [7]).
Often, taxa differ mainly by molecular data and/or geography, see e.g., the key to Virescentia in [7] where V. viride-americana and V. viride-brasiliensis are distinguished as follows: “Known distribution in North America (USA)” versus “Known distribution in South America (Brazil)” [7]. Similar cases occur in Sheathia or Paludicola. Molecular data help to uncover cryptic taxa that are morphologically difficult to distinguish.

Author Contributions

All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by E.F., D.K., K.M. and D.Q. The laboratory work was done by C.S. and J.G. Field work and material collection was done by E.F., D.K., B.L. and D.Q. The first draft of the manuscript was written by E.F. and all authors commented on previous versions of the manuscript. All authors have read and agreed to the published version of the manuscript.

Funding

The molecular work in this research was funded by the GBoL Initiative. (GERMAN BARCODE OF LIFE). GBOL 2, funded by the Federal Ministry of Education and Research (BMBF), project 5, January 2016 to December 2019, http://gbol5.de, grant number 01LI1501F.

Data Availability Statement

Newly generated data available on GenBank, NIH genetic sequence database, https://www.ncbi.nlm.nih.gov/genbank.

Acknowledgments

We are grateful to the GBoL Initiative (German Barcode of Life) for funding of the molecular work. The Struktur- und Genehmigungsdirektion Nord, Koblenz, kindly supplied research and collection permits. Special thanks go to the Chief Warden of the Hunsrück-Hochwald National Park, Harald Egidi, and to Andrea Kaus-Thiel (both National Park Head Office, Birkenfeld), who were always interested in our research and who accompanied us on several field trips. Jan Rommelfanger (also National Park Head Office, Birkenfeld) helped in the coordination of the research. We thank three anonymous reviewers for valuable comments.

Conflicts of Interest

The authors declare no conflicts of interest.

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Diversity 16 00473 g001
Figure 1. Phylogenetic tree based on rbcL and COI sequences. The numbers associated with the nodes indicate the bootstrap values for maximum likelihood (above) and posterior probability for Bayesian (below) analysis. The phylogram of the likelihood analysis is depicted next to the support containing cladogram.
Figure 1. Phylogenetic tree based on rbcL and COI sequences. The numbers associated with the nodes indicate the bootstrap values for maximum likelihood (above) and posterior probability for Bayesian (below) analysis. The phylogram of the likelihood analysis is depicted next to the support containing cladogram.
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Diversity 16 00473 g002
Figure 2. Hoefkenia hunsrueckensis. (A)—habitat in Hunsrück-Hochwald NP, Germany; (B,C)—habit in situ, Ochsenfloß stream; (D,F)—detail of thallus with carposporophytes; (E)—detail of habit; (G)—detail of whorl showing primary and secondary fascicles. ((A–G), Fischer et al. 435/2017, AC 090). Scales: (B,C,E) = 1 cm, (D) = 50 µm, (F) = 250 µm, (G) = 100 µm.
Figure 2. Hoefkenia hunsrueckensis. (A)—habitat in Hunsrück-Hochwald NP, Germany; (B,C)—habit in situ, Ochsenfloß stream; (D,F)—detail of thallus with carposporophytes; (E)—detail of habit; (G)—detail of whorl showing primary and secondary fascicles. ((A–G), Fischer et al. 435/2017, AC 090). Scales: (B,C,E) = 1 cm, (D) = 50 µm, (F) = 250 µm, (G) = 100 µm.
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Figure 3. Hoefkenia hunsrueckensis. (A)—detail of thallus; (B)—carposporangia; (C)—carposporophyte; (D–F,H,I)—detail of thallus with carpogonium and trichogyne; (G)—detail of thallus with young carposporophyte. ((A–I) Fischer et al. 435/2017, AC 090). Scales: (A,C,E–I) = 50 µm, (B) = 10 µm, (D) = 20 µm.
Figure 3. Hoefkenia hunsrueckensis. (A)—detail of thallus; (B)—carposporangia; (C)—carposporophyte; (D–F,H,I)—detail of thallus with carpogonium and trichogyne; (G)—detail of thallus with young carposporophyte. ((A–I) Fischer et al. 435/2017, AC 090). Scales: (A,C,E–I) = 50 µm, (B) = 10 µm, (D) = 20 µm.
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Table 1. Locality data and new GenBank accession numbers.
Table 1. Locality data and new GenBank accession numbers.
SpeciesCountryLocalityElevationDateCollection NumberLab IDrbcLcox1
Bangia atropurpureaGermanyMühlbach in Oberaudorf48017 March 2017WH1AC053PP919124PP919139
Bangia atropurpureaGermanyMühlbach in Oberaudorf48017 March 2017WH2AC054PP919125PP919140
Paludicola turfosaGermanySchwarzwald, Blindensee100716 June 2017s.n.AC050PP919127PP919142
Paludicola turfosaBelgiumHaute Fagne, Sourbrodt61025 April 2017s.n.AC091PP919126PP919141
Batrachospermum gelatinosumBelgiumRur near Küchelscheid50422 April 2017RA001AC043PP919129PP919144
Batrachospermum gelatinosumBelgiumRur, near “Grünkloster”52722 April 2017RA002AC022PP919128PP919143
Batrachospermum gelatinosumBelgiumRur, near “Grünkloster”52722 April 2017RA002AC044PP919130PP919145
Batrachospermum gelatinosumBelgiumRur, near “Grünkloster”52722 April 2017RA002AC045PP919131PP919146
Batrachospermum gelatinosumBelgiumRur, near “Grünkloster”52722 April 2017RA002AC046PP919132PP919147
Hildenbrandia rivularisGermanyAhr, near Blankenheim40522 April 2017RA006AC025PP919138N.A.
Lemanea fluviatilisGermanyAhr, near Lohrsdorf7122 April 2017RA007AC024PP919133PP919148
Lemanea fucinaGermanyAhr, near Dorsel26222 April 2017RA005AC023PP919133PP919149
Hoefkenia hunsrueckensisBelgiumRur, near “Grünkloster”52722 April 2017RA005AC049PP919136PP919151
Hoefkenia hunsrueckensisGermanyHunsrück, Ochsenfloss55111 May 2017s.n.AC051PP919137PP919152
Hoefkenia hunsrueckensisGermanyHunsrück, Thranenweiher58310 August 2017435/2017AC090PP919135PP919150
s.n. = without number. N.A. = not applicable.
Table 2. Accession numbers of rbcL and COI gene sequences used from GenBank.
Table 2. Accession numbers of rbcL and COI gene sequences used from GenBank.
SpeciesAccession Number
rbcLCOI
Audouinella hermanniiKC134346KC130152
Balbiania investiensAF132293KM055323
Bostrychia moritzianaAY920809MF093965
Bostrychia scorpioidesAY920825MF094019
Kumanoa americanaKX284725JN604910
Kumanoa capensisJX504698JX504695
Kumanoa curvataJN590012JN604925
Kumanoa globosporaGQ368891JN604923
Kumanoa virgatodecaisneanaAF029148N.A.
Nocturama antipoditesKT802839KT802754
Nothocladus kraftiiKT802854KT802760
Sheathia boryanaJX669773JX669707
Sirodotia huillensisAF126410EU636739
Tuomeya americanaAF029159KM055330
Virescentia helminthosaKJ825955HQ412541
Virescentia viride-americanaAF244111EU636733
Virescentia viride-brasiliensisKM097039KM260002
Virescentia vogesiaca Bvogst13KJ825953N.A.
Virescentia vogesiaca Bvogst16KJ825954N.A.
Virescentia vogesiaca SpainKU754497N.A.
Visia cayennensisAY423392EU095971
N.A. = not applicable.
Table 3. Morphological differences between Hoefkenia, Kumanoa, Paludicola, Virescentia and Visia.
Table 3. Morphological differences between Hoefkenia, Kumanoa, Paludicola, Virescentia and Visia.
CharacterHoefkeniaKumanoaPaludicolaVirescentiaVisia
Carpogonial brancheswell differentiated from vegetative fascicles, straight, involucral filaments shortcells clearly differentiated from vegetative fascicle cells curved, branches strongly twisted or spirally coiledwell differentiated from the fascicles, straightwell differentiated from the fascicles, branches straight, rarely slightly curvedbranches well differentiated from the fascicles, straight, developing from the periaxial, rarely from proximal cells of primary fascicles
Gonimoblast filamentsonly one type of gonimoblast filaments, which grow radially from the fertilized carpogonia forming a hemispherical or spherical structureonly one type of gonimoblast filaments, which grow radially from the fertilized carpogonia forming a hemispherical or spherical structuregonimoblast filaments of two types: radially branched, densely or loosely arranged, determinate with 2–14 ellipsoidal, cylindrical, or barrel-shaped cells and diffuse, indeterminate with cylindrical cellsonly one type of gonimoblast filaments, which grow radially from the fertilized carpogonia forming a hemispherical or spherical structuregonimoblast filaments of one type of cells, densely arranged, composed of 2–5(–6) cylindrical or barrel-shaped
Trichogyneunstalked to very shortly stalked, club-shapedunstalked or stalked, cylindrical, club-shaped, elliptical, elongate-elliptical, lanceolate or bottle-shapedunstalked club-shapedwith stalked, cylindrical, sub-cylindrical, club-shaped or elliptical trichogynesunstalked to pedicellate, club-shaped or elongate club-shaped, rarely undulated
Carposporophytealways axial central in the whorl, densely arranged and hemispherical in shape, 1 per whorl, very rarely 2always axial central in the whorl and usually hemispherical in shape, 1–2 per whorlaxial, hemispherical to obovoidal, higher or lower than the whorls, 1–2 per whorl, largeaxial-central, hemispherical or spherical, inserted within the whorls, 1–2, rarely 3, per whorl, largepedunculate or short-pedunculate, spherical, spread within the whorls, 1–3 per whorl, small
Table 4. Morphological differences between Hoefkenia and the species of Virescentia.
Table 4. Morphological differences between Hoefkenia and the species of Virescentia.
CharacterHoefkeniaV. crispataV. gulbenkianaV. helminthosaV. viride-americanaV. viride-brasiliensisV. vogesiaca
WhorlsStraight, fascicles with cylindrical cellsCurved audoinelloid fascicles with cylindrical or barrel-shaped cellsStraight, fascicles with cylindrical cellsStraight, fascicles with cylindrical cellsStraight, fascicles with cylindrical cellsStraight, fascicles with cylindrical cellsStraight, fascicles with cylindrical cells
Secondary fasciclesFew and sparseAbundant, covering the entire internodeFew and sparseFew and sparse or abundant and covering the entire internode Few and sparse or abundant and covering the entire internodeFew and sparse or abundant and covering the entire internodeAbundant and covering the entire internode
CarpogoniaWith unstalked to very shortly stalked, club-shaped trichogyne, 35–48 µmWith stalked, cylindrical trichogyne, 54–75 µmWith stalked, cylindrical or club-shaped trichogyne, 20–39 µmWith stalked, cylindrical trichogyne, 40–79 µmWith stalked, cylindrical trichogyne, 40–79 µmWith stalked, cylindrical trichogyne, 40–110 µmWith stalked or shortly stalked, cylindrical trichogyne, 20–45 µm
Carpogonial branchesStraightSlightly curvedStraightSlightly curvedStraightStraightStraight
DistributionWestern Germany, Eastern Belgium, FranceMalaysiaPortugalFinland and Sweden to Spain and PolandCentral to Eastern USASoutheastern to Southern BrazilWestern France, Spain
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Fischer, E.; Killmann, D.; Gerlach, J.; Schütte, C.; Leh, B.; Müller, K.; Quandt, D. Hoefkenia hunsrueckensis, a New Genus and Species from Europe, and the Identity of Virescentia vogesiaca (F.W.Schultz ex Skuja) Necchi, D.C.Agostinho & M.L.Vis (Batrachospermales, Rhodophyta). Diversity 2024, 16, 473. https://doi.org/10.3390/d16080473

AMA Style

Fischer E, Killmann D, Gerlach J, Schütte C, Leh B, Müller K, Quandt D. Hoefkenia hunsrueckensis, a New Genus and Species from Europe, and the Identity of Virescentia vogesiaca (F.W.Schultz ex Skuja) Necchi, D.C.Agostinho & M.L.Vis (Batrachospermales, Rhodophyta). Diversity. 2024; 16(8):473. https://doi.org/10.3390/d16080473

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Fischer, Eberhard, Dorothee Killmann, Johanna Gerlach, Claudia Schütte, Burkhard Leh, Kai Müller, and Dietmar Quandt. 2024. "Hoefkenia hunsrueckensis, a New Genus and Species from Europe, and the Identity of Virescentia vogesiaca (F.W.Schultz ex Skuja) Necchi, D.C.Agostinho & M.L.Vis (Batrachospermales, Rhodophyta)" Diversity 16, no. 8: 473. https://doi.org/10.3390/d16080473

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