Botanists move to rename Europe’s mossy arctic-alpine spring vegetation

In the high mountains of Europe, where icy water seeps from non-calcareous bedrock and mosses carpet the streambeds, a quiet taxonomic dispute has been unfolding for nearly a century. It concerns the name of an alliance of spring vegetation, Cardamino-Montion, first described by the Swiss botanist Josias Braun-Blanquet in 1925. Now, in a formal proposal published in the journal Vegetation Classification and Survey, a team of European vegetation scientists argues that this venerable name should be set aside in favour of a younger one, Philonotidion seriatae, coined by Hinterlang in 1992. The proposal, numbered 36 in the long-running series of nomenclatural proposals under the International Code of Phytosociological Nomenclature, is far more than an academic footnote. It touches on how scientists communicate about some of the rarest and most fragile ecosystems on the continent, and it reveals how the slow evolution of classification concepts can turn even the oldest names into sources of confusion.

The story begins with Braun-Blanquet’s original diagnosis. The holotype of Cardamino-Montion is the association Bryetum schleicheri, published in 1925 and documented in a vegetation table from the Massif Central of France, where the relevés were sampled at elevations between 1350 and 1610 metres above sea level. The dominant taxon in the original diagnosis was Bryum schleicheri, known today as Ptychostomum schleicheri, a circumpolar moss with a distinctly arctic-alpine distribution. The second most abundant species among the faithful character species was Saxifraga stellaris, another predominantly arctic-alpine plant that only rarely descends to lower elevations. Other faithful character species, such as Sagina linnaei and Epilobium nutans, also have their distributional optima in arctic-alpine areas. The arctic-alpine character of the type association is further underlined by the firm character species Philonotis seriata, which co-dominated the moss layer. In contrast, Montia fontana, reported as a firm character species, occurred in all seven relevés but with low abundance, and this taxon has its distributional optimum at lower elevations, where it often dominates, whereas it only rarely occurs in vegetation where arctic-alpine taxa prevail.

As knowledge of the variability of non-calcareous spring vegetation in Europe increased, new alliances were identified. Nordhagen described the Mniobryo-Epilobion hornemannii alliance in 1943, another bryophyte-dominated non-calcareous vegetation with many similarities to Bryetum schleicheri, including the dominance of Philonotis seriata and Saxifraga stellaris. Maas, in 1959, divided Braun-Blanquet’s Cardamino-Montion into two alliances: Cardaminion amarae for shaded springs and Montion for open springs. The latter, however, is a superfluous name under the Code, since its diagnosis contains the Bryetum schleicheri association, which is the nomenclatural type of Cardamino-Montion. Shaded forest springs were then distinguished from non-forest springs at the alliance level in most subsequent vegetation surveys, and they are classified today in the Caricion remotae alliance, the oldest valid name for that unit.

The separation of spring vegetation with arctic-alpine species, dominated by mosses, from colline to montane spring vegetation, dominated by Montia fontana and other vascular plants, was introduced in the synthesis of Czechoslovak spring vegetation by Hadač in 1983. He reported the Cardamino-Montion alliance from the montane zone in the westernmost part of Czechoslovakia, where the arctic-alpine character species of the type association do not occur. For the alpine zone, he described two new alliances: a productive, herb-dominated one, Cratoneuro filicini-Calthion laetae, and a moss-rich one with low productivity, characterized by Philonotis seriata and Diobelonella palustris. Due to obvious differences compared to Cardamino-Montion, including the presence of Allium schoenoprasum, Bartsia alpina, Swertia perennis and Pedicularis sudetica, and the absence of Saxifraga stellaris, Sagina saginoides, Sedum villosum and Montia fontana, Hadač described this moss-rich vegetation as Swertio perennis-Anisothecion squarrosi. Later, in 1992, Hinterlang described another new alliance for bryophyte-dominated arctic-alpine spring vegetation, Philonotidion seriatae, which contains Philonotis seriata, Bryum schleicheri and Saxifraga stellaris, exactly as in Braun-Blanquet’s original description of Cardamino-Montion. Nevertheless, he retained the name Cardamino-Montion for springs with Montia fontana in the broad sense, including Braun-Blanquet’s subalpine association.

Consistent differentiation between bryophyte-dominated arctic-alpine spring vegetation and herb-rich montane spring vegetation with Montia fontana began with the first Europe-wide synthesis of spring vegetation by Zechmeister and Mucina in 1994. In that study, the vegetation of low-elevation springs with Montia fontana was described as the new alliance Epilobio nutantis-Montion. The same solution was adopted in many subsequent studies, and finally also in the European vegetation checklist by Mucina and colleagues in 2016. The name Philonotidion seriatae was placed there, for unspecified reasons, as a synonym of Swertio perennis-Anisothecion squarrosi instead of Cardamino-Montion, with which it shares more diagnostic species. The result is a nomenclatural tangle in which the two name-giving taxa of Cardamino-Montion, Cardamine amara and Montia fontana, no longer indicate the character of the vegetation corresponding to the nomenclatural type of the alliance. Both are actually subordinate taxa with different ecological requirements, and they are instead characteristic of other currently distinguished alliances: Cardamine amara of Caricion remotae and Cratoneuro-Calthion laetae, and Montia fontana of Epilobio nutantis-Montion.

Recently, Peterka and colleagues conducted a new pan-European synthesis of spring vegetation based on original relevé data classified using both unsupervised and supervised methods. This study identified vegetation types that consistently formed distinct clusters in numerical analyses and were reproducible by formal definitions. In most cases, these vegetation types corresponded to the above-mentioned alliances, with one exception: the relevés corresponding to the type associations of Cardamino-Montion and Philonotidion seriatae fell into one group in all cases, even when a fine classification with many clusters was performed. Peterka and colleagues selected the name Philonotidion seriatae for this vegetation, arguing that the name Cardamino-Montion was often used for different vegetation types in the past, including herb-dominated colline to montane Montia springs and even shaded low-elevation springs, making it a source of misunderstanding among vegetation scientists and thus a nomen ambiguum.

A literature survey presented in the proposal shows how the name Cardamino-Montion has been used for very different vegetation types corresponding to different currently distinguished alliances and even orders. Braun-Blanquet himself, in 1926, applied it to subalpine non-calcareous springs. Bartsch and Bartsch, Büker, Tüxen, Maas, Oberdorfer, Lebrun and colleagues, Dierßen, and many others used it for various combinations of subalpine springs, low- and mid-elevation unshaded springs, and forest springs. Zechmeister and Mucina, Mucina and colleagues, Ellenberg and Leuschner, and Schaminée and colleagues each applied the name in yet other ways. Although it is not possible to prove that most of these uses excluded the type of the alliance, it is obvious that different authors understand the name differently. Throughout the history of phytosociology, classification concepts evolved from a single broad alliance towards smaller, ecologically and floristically more homogeneous units at the alliance level.

Applying the rules strictly and maintaining the oldest name Cardamino-Montion would be a constant source of error, the authors argue. Scientists would then have to use two similar but counter-intuitive names: Cardamino-Montion for arctic-alpine springs, although the name-giving taxa occur mainly in montane springs, and Epilobio nutantis-Montion for montane springs, although the name-giving taxon Epilobium nutans occurs mainly in arctic-alpine springs. Therefore, it is likely that the name Cardamino-Montion would gradually become ambiguous. For these reasons, the authors propose conserving the name Philonotidion seriatae against the names Cardamino-Montion of 1925, Cardamino-Montion of 1926, and Montion of 1959. The latter three alliances share a nomenclatural type which is different from the type of Philonotidion seriatae, whose type is the association Cratoneuro-Philonotidetum, described by Geissler in 1976. The lectotype of this association, selected by Hinterlang in 2017, is relevé 11 in table 10 of Geissler’s article.

In addition, the authors propose conserving the name Philonotidion seriatae against the name Mniobryo-Epilobion hornemannii. This will prevent the latter name from being used for a broader alliance containing the nomenclatural types of Cardamino-Montion, Philonotidion seriatae and Mniobryo-Epilobion hornemannii, since Epilobium hornemanii does not occur in most of the distribution range of such a hypothetical alliance. The authors acknowledge that classification systems combining associations to alliances differently than was done in the studies by Zechmeister and Mucina, Mucina and colleagues, and Peterka and colleagues may appear in the future. If the proposal is accepted, then the name Philonotidion seriatae should be used for all species-poor, bryophyte-dominated, non-calcareous spring vegetation types. The name, however, would exclude Cratoneuro filicini-Calthion laetae, which is productive, herb-dominated, and partly transitional to Cardamino-Chrysosplenietalia or even Mulgedio-Aconitetea. It would also exclude Swertio perennis-Anisothecion squarrosi, which is also rich in herbs and partly transitional to Scheuchzerio-Caricetea nigrae. Any hypothetical alliance comprising the latter two herb-rich alliances should therefore be named either Cratoneuro filicini-Calthion laetae or Swertio perennis-Anisothecion squarrosi, depending on its content. The authors consider these names more suitable for such hypothetical alliances than Philonotidion seriatae, as they both contain taxa from the highest vegetation stratum, the herb layer in this case. Finally, a hypothetical alliance combining all non-calcareous springs, regardless of shading and climate, would be named Caricion remotae.

Should the proposal be accepted, the name Cardamino-Montion would remain available for a hypothetical alliance that excludes the type of Philonotidion seriatae, for example an alliance comprising non-calcareous springs regardless of elevation, but excluding vegetation extremely poor in vascular plants or without Montia fontana. The proposal is now formally registered as number 36 in the series of nomenclatural proposals under the International Code of Phytosociological Nomenclature, and it will be considered by the responsible nomenclatural commission. The outcome will determine how scientists name and communicate about the mossy, icy springs of Europe’s high mountains for decades to come. The authors, led by M. H., conceived the idea together and critically revised the manuscript, with M. H. leading the writing. Their proposal is a reminder that even in a field as seemingly settled as botanical nomenclature, the names we use for ecosystems are living tools, shaped by a century of accumulating knowledge, and occasionally in need of careful repair to keep scientific communication precise.

Subject of Research: Proposal (36) to conserve the name Philonotidion seriatae Hinterlang 1992 for the species-poor, bryophyte-dominated, non-calcareous arctic-alpine spring vegetation of Europe

Article Title: Proposal (36) to conserve the name Philonotidion seriatae Hinterlang 1992 for the species-poor, bryophyte-dominated, non-calcareous arctic-alpine spring vegetation of Europe

Article References: Hájek, M., Peterka, T., Hájková, P., Hinterlang, D., Zechmeister, H., & Chytrý, M. (2024). Proposal (36) to conserve the name Philonotidion seriatae Hinterlang 1992 for the species-poor, bryophyte-dominated, non-calcareous arctic-alpine spring vegetation of Europe. Vegetation Classification and Survey, 5, 11-15. https://doi.org/10.3897/vcs.103154

Image Credits: AI Generated

DOI: 10.3897/VCS.103154

Keywords: Proposal, conserve, name, Philonotidion, seriatae, Hinterlang, species-poor, bryophyte-dominated, non-calcareous, arctic-alpine, spring, vegetation