Grimm, Denk & Grimm & Cardoni & Csilléry & Schulze & Simeone & Worth, 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 : 160-162

Fagus subg. Englerianae Denk & G. W. Grimm , subg. nov.

Type: Fagus engleriana Seemen ex Diels in Bot. Jahrb. Syst. 29: 285. 1900.

Molecular diagnosis — The subgenus differs consistently from all species of Fagus subg. Fagus in any sufficiently divergent nuclear marker sequenced so far ( Denk & al. 2002, 2005; Renner & al. 2016; Cardoni & al. 2022). Its polymorphic and notably divergent ITS variants belong to Lineage I as defined in Denk & al. (2005); the sequenced part of the Crabs Claw (CRC) gene and the 2 nd intron of the Leafy gene (LFY) include 14 subgenus-sorted SNPs (see above) in addition to several subgenus-restricted length-polymorphic patterns (see supplementary content, file Genotypification.xlsx, sheets CRC LP-patterns, LFY LP-patterns): an AC tetramer at pos. 1634ff in the CRC reference alignment; a 7 nt-long duplication at pos. 199ff, 45 nt-long deletion at pos. 573ff, and diagnostic oligonucleotide motives at pos. 671–696 and 737–764. Additional subgenus-diagnostic SNPs can be found in 19 of the 28 nuclear loci sequenced by Jiang & al. (2022; cf. supplement to Cardoni & al. 2022, data S5): in P4 at reference alignment (SDA, file RefMatrixJiangEtAlNcLoci.nex) positions 296, 321, 361, 504; P12—pos. 50, 230, 290, 590, 695; P14—pos. 106, 159, 195, 492; P21—pos. 420, 746, 793; P28—pos. 53/54: TC dinucleotide ↔ AT, AC, GC in F. subg. Fagus , pos. 135; P37—pos. 7; P42—pos. 96, 239, 274, 308, 409, 453, 649, 665; P48—pos. 145, 241, 262, 287; P52—71, 86, 90, 165, 243, 272, 407, 455; P54—pos. 82, 313, 616, 683, 703; P69—pos. 85, 130, 204, 251, 267, 406, 475, 542, 656, 737; P72—pos. 40, 91, 222, 306, 334, 387, 412, 415f (TT dinucleotide ↔ CA in F. subg. Fagus ), 593; P97—pos. 236, 305, 394, 427, 467, 684 (C↔T/G); P98—pos. 461, 509; F128—pos. 272, 297, 406, 448, 522, 637, 661; F159—pos. 42, 252; F253—pos. 47, 72, 133, 140, 177; F286—pos. 58, 70, 133, 281; F289—pos. 106, 159, 195, 492; subgenus-diagnostic indels and oligonucleotide motives (including subgenus-restricted allelic variation) can be found in P42—GTCTA at pos. 619ff ↔ AG in F. subg. Fagus ); P48—pos. 544–546: CGT/TGT vs CTG/CGG; P52—pos. 43–54: CAG-tetramer in F. subg. Englerianae, dimer F. subg. Fagus ; P69—TATA at pos. 704–709 vs TAYAAA; F253—GGA at pos. 90ff ↔ GGGA in F. subg. Fagus .

Morphological diagnosis — Multi-stemmed or lowbranching trees; buds stipitate; leaves thin-chartaceous, abaxial leaf surface papillate, abaxial leaf surface with conspicuous wax ornamentation, size of stomata small, subsidiary cells of stomata anomocytic, leaf margin usually without teeth; cupule peduncle medium-long to long; pollen small, colpi long and narrow with rectangular apex.

Species — Three: Fagus engleriana , F. japonica , F. multinervis Makai ; all of which are restricted to East Asia.

Remarks — The name Fagus subg. Englerianae was proposed by the doctoral thesis of Shen (1992) but has not been effectively published. The pollen of modern-day species of F. subg. Englerianae has to be treated as (sym) plesiomorphic (cf. Denk 2003) while leaf anatomical features allow to trace this subgeneric lineage back to the late Eocene, western Japan (Uemura 2002; see also Denk & Grimm 2009).

Revision of Fagus in western Eurasia