The alliance name Agrostion castellanae has been widely used for nearly sixty years to indicate a type of acidophilic perennial grasslands occurring in the Iberian Peninsula. At present, the alliance is classified in the order Agrostietalia castellanae, and the class Stipo giganteae-Agrostietea castellanae. However, the nomenclatural type (lectotype) of the Agrostion castellanae is a therophytic grassland, namely the association Holco setiglumis-Anthoxanthetum aristati, that was consistently classified for two decades by Iberian authors within the therophytic class Helianthemetea guttati. In order to preserve the name Agrostion castellanae in its current use, we propose to designate the association Festuco amplae-Agrostietum castellanae as the conserved type of the alliance.

(32) Agrostion castellanae Rivas Goday 1958 corr. 1964: 353 nom. cons. propos.

Typus: Festuco amplae-Agrostietum castellanae Rivas-Martínez et Belmonte 1986: 418 (typus cons. propos.).

(≡) Agrostion castellano-tenuis Rivas-Goday 1958: 626 nom. inept.

Taxonomic reference: Euro+Med (2023).

Syntaxonomic reference: Mucina et al. (2016).

Abbreviations: EVC = EuroVegChecklist (Mucina et al. 2016); ICPN = 4^th edition of the International Code of Phytosociological Nomenclature (Theurillat et al. 2021).

Agrostion castellanae, conserved name, conserved type, Mediterranean grasslands, Iberian Peninsula, nomenclature, phytosociology

The alliance Agrostion castellano-tenuis was validly published by Rivas Goday (1958: 626–640, sub “Agrostion castellanae-tenuis”), with an original diagnosis consisting of three valid associations: “As. nova Holcus setiglumis et Anthoxanthum aristatum” (p. 627), “As. nova Agrostis truncatula et Periballia laevis” (p. 636), and “As. Agrostis truncatula et Aster aragonensis” (p. 637). Rivas-Goday (1958) also ascribed to the alliance a fourth provisional, and therefore invalid (Art. 3b) association (i.e., “As. Agrostis truncatula et Trisetum ovatum”). Both name-giving taxa of the alliance, namely Agrostis tenuis Sibth. 1974 [recte: Agrostis capillaris L. 1753] and Agrostis castellana Boiss. & Reut. 1842, are listed in the valid elements of its original diagnosis. More precisely, the two species are reported as “Agrostis tenuis castellana” in table 27 in Rivas Goday (1958: 628) that refers to the “As. Holcus setiglumis et Anthoxanthum aristatum”, and as “Agrostis castellana B. et R. (et tenuis)” in table 32 that refers to the other three associations. This means that both taxa, “Agrostis tenuis” and Agrostis castellana, are listed on the same line without being differentiated from each other (see Art. 3g, example 5) since both species are difficult to differentiate morphologically and can hybridize (Romero García 2021).

A few years later, Rivas Goday (1964) corrected the name Agrostion castellano-tenuis to Agrostion castellanae [“Agrostidion castellanae Riv. God. 1957”; recte: Agrostion castellanae Rivas Goday 1958 corr. 1964] by mentioning only “Agrostis castellana B. et R. (et A. hispanica B. et R.)” (A. hispanica Boiss. & Reut. 1852 being a heterotypic synonym of A. castellana) among the diagnostic species of the alliance, and “Agrostis castellana B. et R.” in the table of the sole valid association mentioned (“As. Holcus setosus et Anthoxanthum aristatum”). That table contains the same relevés already published in 1958 with some corrections in the taxon names, like Agrostis castellana Boiss. & Reut. as already mentioned, and Holcus setosus Trin. 1839 instead of H. setiglumis Boiss. et Reut. 1842. Although Rivas Goday (1964) does not explicitly mention the corrected name Agrostion castellanae-tenuis, it is clear from the context that the two alliance names represent the same syntaxonomic concept; in fact, the Agrostion castellanae also includes one of the associations (“Holcus setosus et Anthoxanthum aristatum”) belonging to the original diagnosis of Rivas Goday (1958). The correction of the alliance name due to the misidentification of its name-giving taxon (Art. 43) is valid because an explicit citation of the name to be corrected is not required before 2002. Prior to that date, the citation of the author is sufficient to identify the name to be corrected when it is accompanied by an unambiguous reference to the original publication, as it is the case in Rivas Goday (1964). Therefore, the correct citation of the alliance name is Agrostion castellanae Rivas Goday 1958 corr. 1964.

On the other hand, Rivas-Martínez et al. (2011, p. 290) considered the name Agrostion castellano-tenuis invalidly published by Rivas Goday (1958) due to Article 3f, and indicated the name Agrostion castellanae Rivas Goday ex Rivas-Martínez, Costa, Castroviejo et Valdés 1980 as the first valid name available for the alliance. These interpretations are erroneous because the misidentification of the alliance name giving taxon (i.e. Agrostis tenuis) is a matter of Article 43, not of Article 3f. Since the name Agrostion castellano-tenuis was validly published by Rivas Goday (1958), and later corrected by Rivas Goday (1964), the name “Agrostion castellanae Rivas Goday (1957) 1964” reported by Rivas-Martínez et al. (1980) together with the unambiguous references to Rivas-Goday’s 1958 and 1964 papers, refers precisely to Agrostion castellanae Rivas Goday 1958 corr. 1964. Hence, the name “Agrostion castellanae Rivas Goday et Rivas-Martínez in Rivas-Martínez et al. 1980” cited by Rivas-Martínez et al. (2011) cannot be considered as the name of a new syntaxon; it is a superfluous name for Agrostion castellanae Rivas Goday 1958 corr. 1964 and gets automatically its type (Art. 18c).

Albeit the validity of the name Agrostion castellano-tenuis and its correction as Agrostion castellanae were subject to controversial interpretations over time (Terzi et al., submitted), the first name fell into disuse and the name Agrostion castellanae remained in use for sixty years to indicate an Iberian type of silicicolous perennial grasslands (e.g., Rivas-Martínez et al. 1999, 2001, 2011). Such use of the alliance name is, however, in conflict with its original diagnosis, and in particular with its nomenclatural type. Rivas-Martínez and Belmonte (1986: 418) designated the association “Anthoxantho aristati-Holcetum setiglumis Rivas Goday 1958 nom. inv.” as the type (lectotype) of the alliance “Agrostion castellanae Rivas Goday 1957 corr. Rivas Goday & Rivas-Martínez 1963”, considering the latter name as a replacement name for Agrostion castellano-tenuis Rivas Goday 1958. However, the name “Agrostidion castellanae (Riv. God., 1957), enmd.” in Rivas Goday and Rivas-Martínez (1963) is invalid because the authors do not provide an unambiguous reference to the Agrostion castellano-tenuis Rivas Goday 1958 nor a sufficient diagnosis (Art. 2b). Nevertheless, the typification is effective for the Agrostion castellano-tenuis Rivas Goday 1958, cited unambiguously as nomenclatural synonym by Rivas-Martínez and Belmonte (1986), and consequently for the homotypic Agrostion castellanae Rivas Goday 1958 corr. 1964. Therefore, the nomenclatural type of Rivas Goday’s alliance is the Holco setiglumis-Anthoxanthetum aristati Rivas-Goday 1958.

Rivas-Martínez et al. (2011: 290) incorrectly indicated the “Asphodelo aestivi-Armerietum gaditanae Allier & Bresset 1977 corr. Rivas-Martínez, T.E. Díaz, Fernández-González, Izco, Loidi, Lousã & Penas 2002” as the nomenclatural type (holotype) of the “Agrostion castellanae Rivas Goday ex Rivas-Martínez, Costa, Castroviejo et Valdés 1980”. This alliance name, as mentioned above, is a superfluous name for Agrostion castellanae Rivas Goday 1958 corr. 1964. Therefore, the nomenclatural type of Rivas Goday’s name is the association Holco setiglumis-Anthoxanthetum aristati Rivas-Goday 1958.

The original diagnosis of the Holco setiglumis-Anthoxanthetum aristati includes six relevés (Rivas Goday 1958: 627, table 27). Two of them (relevés 3 and 4), which contain Nardurus patens (Brot.) Hack. 1880 [recte: Micropyrum patens (Brot.) Pilg. 1949], belong to the association Anthoxantho aristati-Micropyretum patentis Belmonte et Sánchez-Mata in Sánchez-Mata 1989, described within the Helianthemion guttati (Sánchez-Mata 1989) and currently subordinated to this alliance within the class Helianthemetea guttati (e.g., Pérez Prieto and Font 2005; Costa et al. 2012; Ribeiro et al. 2012). The remaining four relevés are dominated by annual taxa, such as Anthoxanthum aristatum and Holcus annuus subsp. setiglumis, whereas Agrostis castellana is never recorded with an abundance-dominance value greater than 2 (on the Braun-Blanquet scale). Indeed, the Holco setiglumis-Anthoxanthetum aristati (under the inversion “Anthoxantho aristati-Holcetum setiglumis”) has been ascribed to the alliance Helianthemion guttati, representing therophytic grasslands, by most Iberian authors for the past two decades (e.g., Rivas-Martínez et al. 2001; Pérez Prieto and Font 2005; Costa et al. 2012). Therefore, the nomenclatural type of the Agrostion castellanae does not fit the current use of the alliance name, which is instead associated with “acidophilous perennial grasslands on sandy-loamy soils” (see EVC). According to the current syntaxonomic interpretation of the Anthoxantho aristati-Holcetum setiglumis, a strict application of the rules would lead to consider the Agrostion castellanae an alliance belonging to the class Helianthemetea guttati.

The 3^rd edition of the International Code of Phytosociological Nomenclature (Weber et al. 2000) did not allow the designation of a conserved type to avoid unnecessary changes of commonly used names. As a consequence, when the EVC was published, the names Agrostion castellano-tenuis and Agrostion castellanae were proposed as nomina ambigua and a new alliance name was suggested to replace them (“Festuco amplae-Agrostion castellanae Theurillat ined.”), although it has remained invalidly published. Consistent with its current usage, the Festuco amplae-Agrostion castellanae is classified in the order Agrostietalia castellanae and class Stipo giganteae-Agrostietea castellanae. With the coming into force of the 4^th edition of the ICPN (Theurillat et al. 2021), the new Article 53 gives now the possibility to preserve the widely used name Agrostion castellanae in its current use by selecting a conserved type other than the Holco setiglumis-Anthoxanthetum aristati Rivas Goday 1958. In this way, the current use of the order name Agrostietalia castellanae Rivas Goday ex Rivas-Martínez et al. 1980 (Rivas-Martínez et al. 1980), whose nomenclatural type is the alliance Agrostion castellanae, is also preserved.

Moreover, none of the other two associations in the original diagnosis of the Agrostion castellano-tenuis (and hence of the Agrostion castellanae) is eligible as conserved type. In the “As. Agrostis truncatula et Aster aragonensis” the abundance-dominance value of “Agrostis castellana tenuis” is low, between 1 and 2 (on the Braun-Blanquet’s cover-abundance scale). This association [sub “Astero aragonensis-Agrostietum truncatulae Rivas Goday 1958”] has been ascribed to the Molinerion laevis, and thus to the annual grasslands of the class Helianthemetea guttati (Rivas-Martínez et al. 2001: 108). On the other hand, the association “Agrostis truncatula et Periballia laevis” is transitional between the xerophytic annual-dominated grasslands of Agrostis truncatula Parl. 1850 (reported in the Euro+Med 2023 as Neoschischkinia truncatula (Parl.) Valdés & H. Scholz 2006) and the mesophytic grasslands of Agrostis castellana. In fact, this association name has never been used and was suggested as a dubious name by Rivas-Martínez et al. (2011: 290). Therefore, we propose to preserve the name Agrostion castellanae Rivas-Goday 1958 corr. 1964 (Agrostion castellano-tenuis Rivas-Goday 1958) in its current use by designating a conserved type not belonging to the original diagnosis.

As mentioned above, the name Agrostion castellano-tenuis Rivas-Goday 1958 was corrected to Agrostion castellanae by Rivas-Goday (1964) due to the misidentification of one of its name giving taxa. However, while there is no doubt about the absence of Agrostis capillaris in the unique association mentioned in Rivas Goday (1964), namely the Holco setiglumis-Anthoxanthetum aristati Rivas Goday 1958 (lectotype), this could not be the case for one of the associations of the original diagnosis of the Agrostion castellano-tenuis Rivas Goday 1958, namely the “As. Agrostis truncatula et Periballia laevis”, described with relevés from NW Spain (León and Zamora provinces) where both species are present. Therefore, if it would be proven that Agrostis capillaris occured in the original relevés of Rivas Goday for this association, then the correction Agrostion castellanae Rivas Goday 1958 corr. 1964 would be illegitimate (Def. V, Art. 43).

We propose to preserve the name Agrostion castellanae Rivas-Goday 1958 corr. 1964 (or the corrected illegitimate name Agrostion castellanae Rivas-Goday 1958 corr. 1964 if it would be proven that Agrostis capillaris occured in the relevés of the original diagnosis of the Agrostion castellano-tenuis Rivas Goday 1958) by designating a conserved type that does not belong to the original diagnosis.

Therefore, in order to preserve the name Agrostion castellanae in its current use, namely to represent the “Ibero-Atlantic thermo- to supramediterranean acidophilous perennial grasslands on sandy-loamy soils” (Mucina et al. 2016), we propose to designate the association Festuco amplae-Agrostietum castellanae Rivas-Martínez in Rivas-Martínez et Belmonte 1986 (Rivas-Martínez and Belmonte 1986: 418) as the conserved type (Art. 53) of the Agrostion castellano-tenuis Rivas Goday 1958 nom. inept. and hence of the Agrostion castellanae Rivas Goday 1958 corr. 1964.

At the same time, we propose the conservation of the Agrostion castellanae Rivas Goday 1958 corr. 1964 according to Art. 52, that allows conserving it against homotypic synonyms like the Agrostion castellano-tenuis Rivas Goday 1958.

The Festuco amplae-Agrostietum castellanae was originally conceived to represent the meso- to supramediterranean perennial grasslands dominated by Agrostis castellana (“vallicares”) distributed in the northern half of the Mediterranean Iberian-Atlantic province (Rivas-Martínez and Belmonte 1986) and has been widely accepted by later authors. It is currently classified within the Agrostion castellanae (e.g., Rivas-Martínez et al. 2011: 290; Costa et al. 2012: 46) and is therefore suitable as conserved type.

All the authors have performed the nomenclatural analysis, discussed the nomenclatural problem, debated the proposed solution, and critically revised the manuscript.

Thanks are due to Giovanni Mazzicone (CNR-Bari), Nicolas Fumeaux (Botanical Garden, Geneva), and Séverine Peckeu (Conservatoire botanique national, Bailleul) for helping us in finding references. We also thank Wolfgang Willner and another anonymous reviewer for their suggestions to improve the manuscript. F.F.G. is supported by the Plan Propio of the UCLM (2022-GRIN-34507).

• Massimo Terzi (Corresponding author, massimo.terzi@ibbr.cnr.it), ORCID: https://orcid.org/0000-0001-8801-6733
• Federico Fernández-González (Federico.Fdez@uclm.es), ORCID: https://orcid.org/0000-0003-1234-4065
• Romeo Di Pietro (romeo.dipietro@uniroma1.it), ORCID: https://orcid.org/0000-0003-4983-8931
• Jean-Paul Theurillat (Jean-Paul.Theurillat@unige.ch), ORCID: https://orcid.org/0000-0002-1843-5809