Fagus caspica Denk, 2024

Denk, Thomas, Grimm, Guido W., Cardoni, Simone, Csilléry, Katalin, Schulze, Mirjam Kurz Ernst-Detlef, Simeone, Marco Cosimo & Worth, James R. P., 2024, A subgeneric classification of Fagus (Fagaceae) and revised taxonomy of western Eurasian beeches, Willdenowia 54, pp. 151-181 : 174-175

Fagus caspica Denk & G. W. Grimm, sp. nov.

Holotype: Iran, Gilan province, Deylaman to Siahkal , 37°02'29''N, 49°54'37''E, 1350 m a.s.l., 7 Jun 2011, J. Noroozi 2349 (W [W20180003068 Fig. 14 https://www.jacq.org/detail.php?ID=1383327]; isotype: W [W20180003067 https://www.jacq.org/detail.php?ID=1383326]).

– Fagus sylvatica var. macrophylla Hohen. in Bull. Soc. Imp. Naturalistes Moscou 1838: 259. 1838, pro parte, nom. nud.

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– Fagus sylvatica var. macrophylla Hohen. ex A. DC. in Candolle, Prodr. 16(2): 118. 1864, pro parte.

Fagus hohenackeriana Palib. in Bull. Herb. Boissier, sér. 2, 8: 378. 1908, pro parte.

Fagus sylvatica subsp. hohenackeriana (Palib.) C. F. Shen, Monogr. Fagus : 60. 1992, pro parte, combination not effectively published (Art. 30.9).

Molecular diagnosis — ITS variants belonging to Lineage IV, possibly specific (based on limited individual-level and old sequence data). 5S-IGS variants predominately specific, typically not shared with any other western Eurasian species but least evolved, i.e. relatively close to the putative ancestral sequence variants; B lineage variants slightly more abundant or nearly as abundant as A lineage variants, and equally diverse ( Fig. 5; Cardoni & al. 2022), no European A and European B variants; A Lineage variants predominately of the Shared A type, types shared with Fagus hohenackeriana p.p. rare (Eastern A) to very rare (Hohenackeriana A2); B Lineage variants dominated by the (originally specific?), derived Caspica B 1 type, and the underived, cross-species shared Ancestral B1/Shared B 1 types ( Fig. 6, 7), the high abundance of the latter is a genotypic characteristic of F. caspica and to a lesser degree, F. orientalis ; no Western B1/Hohenackeriana B1b types. Very distinct isoenzyme ( Gömöry & Paule 2010) and homogenous nuclear SSR profiles ( Kurz & al. 2023), separating F. caspica from its putative sister species F. hohenackeriana at k =4 (see also Sękiewicz & al. 2022, k =2 vs k =3; mapped in Fig. 3). Lineage Va plastomes (species-level plastid type V-EO). CRC distinct from Fagus sylvatica , differing in at least five alignment patterns, three species-consistent SNPs (pos. 800, 85, 1674 in reference alignment) and two to three other (cf. supplementary content, file Genotypification.xlsx, sheet CRC LP-patterns); A-dominated motif at position 830–859 in CRC near-exclusively composed of A (terminating on G, GG, TG in all other species). No LFY or low-copy nuclear loci data so far. Lineage Va plastomes, differing by 564–642 SNPs from the plastomes of their westernmost cousin, F. sylvatica (Lineage Vb plastomes), about the same level of difference as found in East Asian individuals carrying the same plastome lineage (Japanese Lineage II median: 637 SNPs; East Asian Lineage IV median: 462 SNPs) and about half of the maximum difference recorded so far (1198 SNPs between Lineage I plastome of F. grandifolia from Michigan and a Lineage IV F. crenata plastome; supplementary content, file Genotypification.xlsx, sheet PlstmDissim).

Morphological description — Lamina shape ovate to elliptic, usually asymmetric, (60–)80–120(–140) mm long, leaf index 188; leaf petiole (2–) 7–12 mm long; most frequent base/apex pairs “cordate asymmetric or symmetric base and attenuate apex”; basal leaf margin entire to wavy, sometimes with blunt teeth, apical margin commonly with prominent teeth; teeth (1) with long, convex, concave or straight basal side and short, steep apical side, or (2) small, pronounced teeth with slightly convex margin between two consecutive teeth; number of secondary veins (7–)8–14(–16); secondary venation brochidodromous to pseudocraspedodromous basally, semicraspedodromous to craspedodromous apically; length of stomata (16–)20– 26(–30) µm, mean 23 µm, subsidiary cells incomplete cyclocytic to actinocytic, with transitions to anomocytic; cupule peduncle (5–)9–25(–40) mm, mean value 17 mm, length of cupule 5–29 mm, mean value 17 mm, basal cupule appendages parallelodromous, membranous, reddish-brown, narrow, similar to bud scales or thread-like ( Fig. 12:D), or narrow spathulate brownish leaflets with obtuse, forked or acute apex, apical appendages woody spine-like, sometimes forming clusters.

Distribution — SE Azerbaijan (Talysh), N Iran.

Evolutionary significance — Genetically, the Iranian populations are the leftover of the initial speciation processes within the precursor(s) of all western Eurasian beeches, as reflected by their many private 5S-IGS variants. The difference between their plastomes and those of Fagus sylvatica is double to triple as high as observed between East Asian species carrying Lineage IV plastomes, which includes the plastomes of all Chinese and Taiwanese beeches and the southeastern populations of the Japanese beeches (cf. Worth & al. 2021). Morphologically, the numerous, densely spaced secondary veins, the usually distinctly serrate leaf margin, and the elongate leaf apex resemble fossils from Middle Miocene strata of Austria and Russia (Zetter 1984; Yakubovskaya 1975). Denk (1999a), furthermore, pointed out leaf morphological similarities with North American populations of F. grandifolia , a likely symplesiomorphic pattern.

Etymology — The species name refers to the distribution of the species along the southern shores of the Caspian Sea in Azerbaijan and northern Iran.

Representative specimens — R. Hohenacker 2229 (P [P06812042]); T. Alexeenko (MW [MW0660538]); A. Ghorbani & A. Pirani 1196 (TMRC [TMRC0001196]); K. H. Rechinger 20006 ( US [NMNH-03400239]); D. Lyskov & T. Krutenko (MW [MW0754378]); A. A. von Bunge (G [G00754877]); J. Lamond 2966 (E [E00401560]); J. Lamond 5136 (E [E00401553]); P. M. R. Aucher-Eloy 5325 (P [P06812078]); D. Walton 242 (E [E00400275]); D. Walton 243 (E [E00401554]); H. de Hell (P [P06812075]); I. V. Palibin (K [K00832763]).