ISSN 1346-7565 Acta Phytotax. Geobot. 72 (2): 113–123 (2021) doi: 10.18942/apg.202017

Taxonomic Revision of subsp. mongolicoides

1,* 1 2 3 Mineaki Aizawa , Kaya Maekawa , Hiroko Mochizuki and Kazuya Iizuka

1Department of Forest Science, School of Agriculture, University 350, Mine-machi, Utsunomiya, Tochigi 321-8505, . *[email protected] (author for correspondence); 2Department of Forest Science, Graduate School of Agriculture, Utsunomiya University 350, Mine-machi, Utsunomiya, Tochigi 321-8505, Japan; 3Utsunomiya University Forests, School of Agriculture, Utsunomiya University, 7556 Funyu, Shioya, Tochigi 329-2441, Japan

Quercus serrata subsp. mongolicoides of the Tokai and northern Kanto districts of Honshu, Japan, is similar to Q. mongolica var. mongolica in leaf morphology. Its taxonomic treatment has been long de- bated, and yet its genetic differentiation from three related taxa, Q. serrata subsp. serrata, Q. mongolica var. crispula, and Q. mongolica var. mongolica has remained unresolved. Genetic differentiation among the four taxa using 11 nuclear microsatellite loci and comparison of leaf morphology was used to revise the taxonomic treatment of Q. serrata subsp. mongolicoides. The genetic data and leaf morphology sup- port the transfer of Q. serrata subsp. mongolicoides from Q. serrata to Q. mongolica. Within the latter, it is treated as a separate intraspecific taxon distinct from Q. mongolica var. crispula in leaf, acorn, and cupule morphology. Additionally, it is geographically well separated from Q. mongolica var. mongolica on the Asian continent and shows significant genetic and leaf differences from the typical variety. Thus, Q. mongolica var. mongolicoides is proposed as a new combination.

Keywords: leaf morphology, nuclear microsatellite, var. crispula, Quercus mongolica var. mongolica, Quercus mongolica var. mongolicoides, Quercus serrata subsp. serrata

Quercus mongolica Fisch. ex Ledeb. is com- gensis (Koidz.) Nakai [syn.: var. undulatifolia (H. mon in temperate deciduous forests of the Asian Lev.) Kitam. & T. Horik.] and Q. crispula var. continent [northeast China, northern China, Rus- horikawae H. Ohba (there is no combination un- sia (Far East) and the Korean peninsula], Japan der Q. mongolica). Var. liaotungensis was recog- and adjacent islands (southern Sakhalin and the nized as a separate species, Q. liaotungensis, southern Kuril Islands) (Miyabe & Kudo 1925, based on genetic differences and reproductive Kitamura & Horikawa 1951). Quercus mongolica isolation from var. mongolica (syn: Q. wutaishan- has been considered to comprise both a large- ica Mayr; Zeng et al. 2010, Chen et al. 2017, Liao leaved arborescent group and a small-leaved ar- et al. 2019), a treatment we follow. borescent to shrubby group (Kitamura & Hori- In Japan, in addition to Quercus mongolica kawa 1951, Ohba 1989); the former consisting of var. crispula of the arborescent group, , two varieties: mongolica on the Asian continent which are characterized by rounded leaf serra- and crispula (Blume) H. Ohashi [Q. mongolica tions similar to Q. mongolica var. mongolica var. grosseserrata (Blume) Rehder & E. H. Wil- from the Asian continent, have been reported to son] in the Japanese archipelago and the adjacent occur on low-lying hills in impoverished areas of Kuril Islands and Sakhalin (Ohashi 1988). The the Tokai and northern Kanto districts in Honshu two varieties have often been considered to be (Inami 1966, Satori et al. 1981; Fig. 1). Ohba distinct species (e.g. Ohba 2006), but here we fol- (2006), based on the morphology and possibly low Ohashi (1988) for nomenclature. The arbo- following the unpublished data in Kanno et al. rescent to shrubby group comprises var. liaotun- (2004), described those plants as Q. serrata 114 Acta Phytotax. Geobot. Vol. 72

Murray subsp. mongolicoides H. Ohba. Serizawa taxa. Based on the results, we here revise the tax- (2008) later proposed the new combination and onomy of Q. serrata subsp. mongolicoides. status, var. mongolicoides (H. Ohba) Seriz., based on morphological simi- larities with Q. crispula. Hiroki (2017) proposed Materials and Methods specific status, Q. mongolicoides (H. Ohba) Hiroki, for these plants based on differences in Samples leaf, acorn and cupule morphology, and differ- Details of the four taxa sampled for analysis ences in root elongation between it and Q. mon- of the genetics and leaf morphology are shown in golica var. crispula. Table 1. For the genetic analyses, 144 , com- Previous studies explored the genetic and prising 54 of Quercus serrata subsp. serrata, 34 morphological delimitation of Quercus serrata of Q. serrata subsp. mongolicoides, 23 of Q. mon- subsp. mongolicoides. Mochizuki et al. (2013) golica var. crispula, and 33 of Q. mongolica var. analyzed five nuclear microsatellite loci and leaf mongolica were used (Table 1). Samples of morphology of populations of Q. serrata subsp. Q. serrata subsp. serrata from sites S1 and S2 mongolicoides, Q. serrata subsp. serrata, and and of Q. mongolica var. crispula from sites S2 Q. mongolica var. grosseserrata (Q. mongolica and S3, which were originally collected by Mo- var. crispula) in and proposed chizuki et al. (2013), and samples of Q. serrata that Q. serrata subsp. mongolicoides should not subsp. serrata from site T, collected for the pres- be treated as an intraspecific taxon of Q. serrata, ent study, were analyzed using 11 nuclear micro- but rather as an intraspecific taxon of Q. mongol- satellite loci. Genotype data obtained by Aizawa ica. Mochizuki et al. (2013) did not analyze or et al. (2018) for Q. serrata subsp. mongolicoides, compare Q. serrata subsp. mongolicoides with based on samples from sites S1 and T and Q. mongolica var. mongolica from the Asian con- Q. mongolica var. mongolica from sites DA, MA tinent. Later, Aizawa et al. (2018) analyzed 11 nu- and DO, were reused in our analyses. clear microsatellite loci and the leaf morphology Two hundred and six trees, comprising 62 of of Q. serrata subsp. mongolicoides (two popula- Quercus serrata subsp. serrata, 30 of Q. serrata tions in Tochigi and Aichi prefectures), Q. mon- subsp. mongolicoides, 75 of Q. mongolica var. golica var. crispula, and Q. mongolica var. mon- crispula and 39 of Q. mongolica var. mongolica golica across northeast Asia and concluded that were used to analyze leaf morphology (Table 1). Q. serrata subsp. mongolicoides may have origi- Data for Q. serrata subsp. serrata from sites S1 nated from an admixture between Q. mongolica and S2 were reused from Mochizuki et al. (2013) var. crispula and Q. mongolica var. mongolica. and supplemented with data on the density of They (Aizawa et al. 2018) analyzed only a small simple hairs collected for the present study. All sample of Q. serrata subsp. serrata. The genetic morphological data for Q. serrata subsp. serrata differentiation among the four taxa, Q. serrata from site T were collected for the present study. subsp. serrata, Q. serrata subsp. mongolicoides, Data for the remaining taxa, including Q. serrata Q. mongolica var. crispula, and Q. mongolica subsp. mongolicoides, Q. mongolica var. crispu- var. mongolica (Fig. 1) has therefore remained la, and Q. mongolica var. mongolica, were reused unknown. from Aizawa et al. (2018). In our study, we analyzed the samples of the Quercus serrata subsp. serrata occurs sym- four taxa, comprising the populations used in the patrically with Q. serrata subsp. mongolicoides study by Mochizuki et al. (2013), the genotype at sites S1 and T and with Q. mongolica var. data collected by Aizawa et al. (2018) and an ad- crispula at site S2. The natural distribution of ditional population of Quercus serrata subsp. Q. aliena Blume and Q. dentata Thunb., which serrata using 11 nuclear microsatellite loci. We are close relatives of the four taxa used in the also compared the leaf morphology of the four present study, do not occur around these sites June 2021 Aizawa & al. — New Name: Quercus mongolica var. mongolicoides 115

Table 1. Taxa, sampling location, and number of samples (N) used for genetic (G) and leaf morphological (M) analyses. N Data† Taxon Locality G M G M Quercus serrata subsp. serrata S1 University Forest Funyu, Shioya, Tochigi, Japan 24 23 1 3 S2 Prefectural forest, Yaita, Tochigi, Japan 20 24 1 3 T Prefectural forest, Toyota, Aichi, Japan 10 15 1 1 54 62 Q. serrata subsp. mongolicoides S1 University Forest Funyu, Shioya, Tochigi, Japan 16 15 2 2 T Prefectural forest, Toyota, Aichi, Japan 18 15 2 2 34 30 Q. mongolica var. crispula S2 Prefectural forest, Yaita, Tochigi, Japan 14 – 1 – S3 Mt. Takahara, Shioya, Tochigi, Japan 9 – 1 – Five populations across Japan – 75 – 2 23 75 Q. mongolica var. mongolica DA Dailing, Heilongjiang, China§ 10 9 2 2 MA Mao’ershan, Heilongjiang, China§ 9 8 2 2 DO Dongjingcheng, Heilongjiang, China§ 14 7 2 2 Blagovershchensk, Amur, Russia – 15 – 2 33 39 144 206 † Data source: 1, data obtained in this study; 2, data obtained from Aizawa et al. (2018); 3, data obtained from Mochizuki et al. (2013), but density of short hairs (≤ 1 mm) and long hairs (> 1 mm) on main vein was assessed in this study. § Planted trees in plantation of Uryu Experimental Forest, Hokkaido University, were used as representatives of Q. mongolica var. mongolica in China.

Fig. 1. Leaves of Quercus serrata subsp. serrata, Q. serrata subsp. mongolicoides, Q. mongolica var. crispula, and Q. mongolica var. mongolica used in this study. Scale bar = 5 cm. Collection site IDs in parentheses correspond to those in Table 1. 116 Acta Phytotax. Geobot. Vol. 72

Table 2. Number of alleles detected (NA) and expected heterozygosity (HE) at 11 nuclear microsatellite loci in Quercus serrata subsp. serrata (QSS), Q. serrata subsp. mongolicoides (QSM), Q. mongolica var. crispula (QMC), and Q. mongolica var. mongolica (QMM), and genetic differentiation measures among the four taxa. QSS QSM QMC QMM Genetic differentiation Loci (N = 54) (N = 34) (N = 23) (N = 33)

NA HE NA HE NA HE NA HE FST GST G'ST CcC00610 20 0.883 17 0.910 17 0.909 15 0.872 0.035 ** 0.020 ** 0.300 ** CcC00660 13 0.837 15 0.874 15 0.885 18 0.897 0.037 ** 0.025 ** 0.293 ** CcC01513 13 0.884 11 0.786 11 0.624 13 0.884 0.052 ** 0.041 ** 0.272 ** QmC00419 5 0.363 5 0.458 4 0.271 5 0.197 0.428 ** 0.420 ** 0.693 ** QmC00716 10 0.529 16 0.891 12 0.877 18 0.912 0.116 ** 0.105 ** 0.722 ** QmC00898 8 0.722 10 0.759 10 0.809 8 0.807 0.048 ** 0.037 ** 0.216 ** QmC00932 12 0.800 15 0.889 14 0.888 15 0.833 0.067 ** 0.053 ** 0.524 ** QmC01368 8 0.605 8 0.504 7 0.696 11 0.778 0.034 ** 0.023 ** 0.080 ** QmC01794 2 0.088 8 0.821 8 0.796 7 0.801 0.189 ** 0.178 ** 0.596 ** QmC02052 9 0.778 9 0.797 10 0.801 9 0.693 0.026 ** 0.013 ** 0.076 ** QmC02269 8 0.766 10 0.806 10 0.794 16 0.848 0.050 ** 0.039 ** 0.268 ** 9.8 0.660 † 11.3 0.772 † 10.7 0.759 † 12.3 0.775 † 0.088 ** 0.076 ** 0.388 ** † Averaged over loci; ** P < 0.001

(Botany Section of Natural Environment Re- ysis using the 11 nuclear microsatellite loci for search Group of Tochigi Prefecture 2003, Ko- the samples was conducted with multiplex poly- bayashi 2012, Mochizuki et al. 2013). Cultivated merase chain reaction following the methodology trees from the plantation of the Uryu Experimen- described by Aizawa et al. (2018). tal Forest, Hokkaido University, were used as The total number of alleles detected (NA) and representatives of Quercus mongolica var. mon- expected heterozygosity (HE) in each taxon and golica (Aizawa et al. 2018). measures of genetic differentiation among the

four taxa (FST, GST, and G’ST) were assessed at Nuclear microsatellite analyses each locus using GenAlEx v.6.503 (Peakall & Previous DNA analyses of species of Quercus Smouse 2006, 2012). The statistical significance indicated that chloroplast DNA was not ideal for of the genetic differentiation measures was also discriminating species because of the extensive tested using GenAlEx. The genetic structure was sharing of chloroplast DNA variants among dif- explored using principal coordinate analysis ferent species. Such sharing is thought to have re- (PCoA) implemented in GenAlEx based on the sulted from hybridization and introgression ow- genetic distance matrix among individual trees ing to their propensity for species of Quercus to (Smouse & Peakall 1999). The genetic structure cross and/or from preservation of ancestral poly- was also analyzed using STRUCTURE v.2.3.4 morphism (Petit et al. 2003, Muir & Schlötterer (Pritchard et al. 2000, Falush et al. 2003, Hubisz 2005, Matsumoto et al. 2009). In contrast, the use et al. 2009) by estimating the allele frequencies of of nuclear microsatellites is useful for species each gene pool (cluster) and the population mem- discrimination among species of Quercus (Muir bership of each individual. We used an admixture et al. 2000, Zeng et al. 2010, Jose-Maldia et al. model and a correlated allele frequency model. 2017, Nagamitsu et al. 2019). We therefore uti- The sampling location information was used as a lized the 11 nuclear microsatellite loci that had prior. STRUCTURE was run 10 times indepen- been used by Aizawa et al. (2018) (Table 2). Anal- dently for each number of clusters (K) (ranging June 2021 Aizawa & al. — New Name: Quercus mongolica var. mongolicoides 117

Fig. 2. Results of principal coordinate analysis obtained using 11 nuclear microsatellite loci from Quercus serrata subsp. serrata, Q. serrata subsp. mongolicoides, Q. mongolica var. crispula, and Q. mongolica var. mongolica. Collection site IDs correspond to those in Table 1. from 1–6) using 100,000 Markov chain Monte (Appendix 1), density of stellate hairs on the ab- Carlo iterations after a burn-in period of 100,000 axial leaf surface (0, none; 1, 1–10; 2, 11–100; 3, > iterations. The optimal number of clusters, K, 100) within a 6 mm diameter circle and density of was determined using two methods based on the short hairs (≤ 1 mm) and long hairs (> 1 mm) on change of mean log likelihoods of the data, the main vein (0, none; 1, 1–10; 2, 11–100; 3, > lnP(D) (Pritchard et al. 2000) and the rate of 100) within a 6 mm diameter circle. The median change in lnP(D), ΔK (Evanno et al. 2005). The was calculated for each taxon based on Aizawa et results of 10 independent runs for the optimal K al. (2018) and the range was determined for each were summarized using STRUCTURE HAR- leaf characteristic. The Steel-Dwass test in R was VESTER (Earl & vonHoldt 2012), CLUMPP v.1.1 used for nonparametric multiple comparisons be- (Jakobsson & Rosenberg 2007), and DISTRUCT tween the four taxa. v.1.1 (Rosenberg 2004). The genetic differentia- tion measure (FST; Weir & Cockerham 1984) and 95% confidence interval (CI) among the four taxa Results was assessed using hierfstat (Goudet 2005) in R (R Core Team 2018). The statistical significance Nuclear microsatellite analyses of the FST values was tested with 1,000 boot- The nuclear microsatellite loci used in the straps. present study were highly variable (NA = 9.8–12.3

and average HE = 0.660–0.775; Table 2). The Morphological analysis of leaves overall values of the genetic differentiation mea-

Based on Mochizuki et al. (2013) and Aizawa sures FST, GST, and G’ST were 0.088, 0.076, and et al. (2018), eight leaf characteristics were com- 0.388, respectively, among the four taxa (Table 2). pared among the four taxa: blade (lamina) length The results of the PCoA indicated that Quercus (BL), maximum blade width (BW), distance to serrata subsp. serrata was clearly distinguish- the widest point from the apex (DWP), able from the other three taxa, Q. serrata subsp. length, number of lateral veins on one side of the mongolicoides, Q. mongolica var. crispula, and main vein of a leaf (NLV), their ratios BW/BL, Q. mongolica var. mongolica (Fig. 2), whereas the DWP/BL, and NLV/BL, shape of leaf serrations latter three taxa were not separated from each 118 Acta Phytotax. Geobot. Vol. 72

Table 3. Pairwise genetic differentiation measure (FST; Weir & Cockerham 1984) and 95% confidence interval (within paren- theses) based on 11 nuclear microsatellite loci for Quercus serrata subsp. serrata (QSS), Q. serrata subsp. mongolicoides (QSM), Q. mongolica var. crispula (QMC), and Q. mongolica var. mongolica (QMM). QSS QSM QMC QSS QSM 0.162 (0.071–0.280) *** QMC 0.192 (0.078–0.331) *** 0.012 (0.005–0.020) *** QMM 0.171 (0.061–0.320) *** 0.020 (0.011–0.033) *** 0.029 (0.011–0.049) *** *** P < 0.001

Fig. 3. Results of STRUCTURE analysis at K = 2 and K = 3 obtained using 11 nuclear microsatellite loci for Quercus serrata subsp. serrata, Q. serrata subsp. mongolicoides, Q. mongolica var. crispula, and Q. mongolica var. mongolica. Each individual is represented by a thin vertical line. Collection site IDs correspond to those in Table 1. other in the PCoA plot. The STRUCTURE analy- average rate of 34–65% in each population, sug- sis indicated that an optimal number of clusters gesting genetic admixture between Q. mongolica (K) would be two on the ΔK method and three var. crispula and Q. mongolica var. mongolica. based on the change of mean lnP(D). At K = 2, The pairwise FST values among the four taxa Quercus serrata subsp. serrata was clearly dis- significantly deviated from zero at all loci exam- tinguished from the other three taxa and at K = 3, ined (P < 0.001), denoting a significant genetic

Q. mongolica var. crispula exhibited a gene pool differentiation (Table 3). The pairwise FST values in light gray at an average rate of 83–93 % in each between Quercus serrata subsp. serrata and the population and was separated from Q. mongolica other three taxa (0.162–0.192) were significantly var. mongolica, which exhibited a gene pool in higher than those among the other three taxa light gray at an average rate of 1–2 % in each pop- (Q. serrata subsp. mongolicoides, Q. mongolica ulation (Fig. 3). Quercus serrata subsp. mongoli- var. crispula, and Q. mongolica var. mongolica; coides exhibited a gene pool in light gray at an 0.012–0.029; Table3), based on the non-overlap of June 2021 Aizawa & al. — New Name: Quercus mongolica var. mongolicoides 119

95% CI between the lower limits of the former much lower than those based on nuclear micro- (0.061–0.078) and the upper limits of the latter satellite loci between species of Quercus on Hok-

(0.020–0.049; Table3). Among the three taxa, the kaido (Table S1 in Nagamitsu et al. 2019), FST = pairwise FST value between Quercus serrata sub- 0.133 (Q. mongolica var. crispula vs. Q. dentata), sp. mongolicoides and Q. mongolica var. crispula FST = 0.153 (Q. mongolica var. crispula vs. Q. ser-

(FST = 0.012) was smaller than between the for- rata var. serrata) and FST = 0.211 (Q. dentata vs. mer and Q. mongolica var. mongolica (FST = Q. serrata var. serrata). The pairwise FST values

0.020) and between Q. mongolica var. crispula among the above three taxa (FST = 0.012–0.029; and Q. mongolica var. mongolica (FST = 0.029). Table 3) were also lower than those observed be- Those values, however, were not significantly tween Q. petraea (Matt.) Liebl. and Q. robur L. in different because their 95% CIs overlapped Europe (FST = 0.050; Muir & Schlötterer 2005) (Table 3). and between Q. mongolica and Q. liaotungensis

in China (FST = 0.069; Zeng et al. 2010). The re- Morphological analysis of leaves sults from our study therefore do not support The comparison of leaf morphology of the treating Q. serrata subsp. mongolicoides as a dis- four taxa indicated that Quercus serrata subsp. tinct species (Q. mongolicoides; Hiroki 2017), serrata was distinguished from the other three and also do not support the species status of taxa, particularly in having a longer petiole, mu- Q. crispula and the inclusion of Q. serrata subsp. cronate serrations (= 1.0; Table 4) and dense stel- mongolicoides as a variety within Q. crispula late hairs on the abaxial surface of the leaf (Table (Q. crispula var. mongolicoides; Serizawa 2008). 4). Quercus serrata subsp. mongolicoides was Quercus serrata subsp. mongolicoides and more similar to Q. mongolica var. mongolica than Q. mongolica var. mongolica are similar in leaf to Q. serrata subsp. serrata and Q. mongolica morphology (Table 4; Aizawa et al. 2018), ovoid var. crispula, particularly in having leaves with a acorns and cupules with prominently humped more rounded serrations (= 5.0; Table 4) and lack scales (Iizuka et al. 2008, Suda & Hoshino 2008, of, or few, stellate hairs on the abaxial surface of Kobayashi 2012, Hiroki 2017). However, our the leaf. However, Q. serrata subsp. mongolicoi- study and the study of Aizawa et al. (2018) indi- des was distinguished from Q. mongolica var. cate that Q. serrata subsp. mongolicoides is ge- mongolica in having a higher NLV and simple netically closer to Q. mongolica var. crispula hairs less dense on the main vein (Table 4). than to Q. mongolica var. mongolica, although

their pairwise FST values were not significant based on the 95% CIs (Table 3). The morphologi- Discussion cal and genetic similarity of Q. serrata subsp. mongolicoides to both var. mongolica and var. The taxonomic treatment of Quercus serrata crispula may be attributed to a potential admix- subsp. mongolicoides has long been debated (Ser- ture between var. crispula and var. mongolica, izawa 2008, Suda & Hoshino 2008, Hiroki 2017). the latter of which may represent relict popula- Our study, which concurred with the results of tions from the Late Pleistocene in and around Ja- Mochizuki et al. (2013), showed that genetic data pan (Aizawa et al. 2018). We therefore propose and leaf morphology of Q. serrata subsp. mon- that Q. serrata subsp. mongolicoides should be golicoides do not support its placement within treated as an intraspecific taxon of Q. mongolica Q. serrata, but rather as an intraspecific taxon of because it differs in leaf, acorn, and cupule mor- Q. mongolica (Figs. 2 & 3; Tables 3 & 4). We also phology from Q. mongolica var. crispula (Table found a low level of genetic differentiation among 4; Ohba 2006, Suda & Hoshino 2008). There is Q. serrata subsp. mongolicoides, Q. mongolica also low but significant genetic differentiation var. crispula, and Q. mongolica var. mongolica between Q. serrata subsp. mongolicoides and

(FST = 0.012–0.029; Table 3). The FST values were Q. mongolica var. mongolica (Table 3). The two 120 Acta Phytotax. Geobot. Vol. 72

Table 4. Median and range of each leaf morphological characteristic in Quercus serrata subsp. serrata, Q. serrata subsp. mongolicoides, Q. mongolica var. crispula, and Q. mongolica var. mongolica. Distance to the Maximum Blade length widest point Number of lateral Taxon N blade width Petiole length BW/BL (BL, cm) from the top veins (NLV) (BW, cm) (DWP, cm)

Q. serrata subsp. 62 10.3 (7.4–13.5) a 4.9 (3.3–6.8) a 1.3 (0.8–1.9) a 4.6 (3.2–5.9) a 13.0 (10.3–16.3) a 0.5 (0.4–0.7) a serrata Q. serrata subsp. 30 15.2 (10.3–25.0) b 9.7 (7.1–16.0) b 0.5 (0.3–0.7) b 6.2 (4.3–10.5) b 14.0 (10.0–18.0) a 0.6 (0.5–0.8) b mongolicoides Q. mongolica var. 75 14.1 (9.9–17.7) c 7.7 (5.5–10.4) c 0.3 (0.1–0.7) c 6.0 (4.4–7.9) b 16.0 (12.0–21.0) b 0.5 (0.4–0.7) c crispula Q. mongolica var. 39 13.1 (9.0–18.6) d 8.1 (4.3–11.0) c 0.5 (0.2–0.8) b 5.0 (3.3–7.0) a 10.0 (6.0–12.0) c 0.6 (0.4–0.8) b mongolica

Density of simple Shape of leaf Density of Taxon N DWP/BL NLV/BL † hairs on the main Data Source serrations stellate hairs § vein

Q. serrata subsp. 62 0.5 (0.4–0.6) a 1.3 (1.0–1.9) a 1.0 (1.0–2.0) a 3.0 (3.0–3.0) a 3.0 (2.0–3.0) a Mochizuki et al. serrata (2013); this study Q. serrata subsp. 30 0.4 (0.4–0.5) b 0.9 (0.6–1.2) b 5.0 (4.0–7.0) b 0.0 (0.0–1.0) b 0.0 (0.0–1.0) b Aizawa et al. mongolicoides (2018) Q. mongolica var. 75 0.4 (0.3–0.5) b 1.2 (0.8–1.5) c 3.0 (2.0–5.0) c 2.0 (0.0–3.0) c 2.0 (0.0–3.0) c Aizawa et al. crispula (2018) Q. mongolica var. 39 0.4 (0.3–0.4) c 0.8 (0.4–1.2) d 5.0 (3.0–7.0) b 0.0 (0.0–0.0) b 1.0 (0.0–2.0) d Aizawa et al. mongolica (2018)

The ranges from minimum to maximum values are shown in parentheses. Different letters in each characteristic indicate significant differences between taxa based on Steel-Dwass multiple comparison tests (P < 0.05). † See Appendix 1. § Dense short hairs (≤1 mm) with sparse or somewhat dense long hairs on the main vein in Q. serrata subsp. serrata and various densities of long hairs (>1 mm) without short hairs on the main vein in Q. serrata subsp. mongolicoides, Q. mongolica var. crispula, and Q. mongolica var. mongolica.

taxa are separated geographically and differ in of Q. mongolica in northeast Asia. some morphological traits, such as NLV and den- Trees with rounded leaf serrations similar to sity of simple hairs on the main vein (Table 4). Quercus mongolica var. mongolica in the coastal We therefore propose the new combination regions of northern Hokkaido (Miyabe & Kudo Quercus mongolica var. mongolicoides for these 1925, Shimizu 1997) are considered to be hybrids plants. between Q. mongolica var. crispula and Q. den- We and Aizawa et al. (2018) did not analyze tata (e.g., Ohba 2006). The origin of those plants Quercus mongolica (var. mongolica and/or var. have remained obscure, but Nagamitsu et al. crispula; Nakai 1915, Kitamura & Horikawa (2019, 2020) showed that such plants were 1951) on the Korean Peninsula, except in compar- derived through introgression from Q. dentata to ing the Q. mongolica chloroplast DNA haplo- Q. mongolica var. crispula. Therefore, this taxon, types from South Korea by Aizawa et al. (2018). Q. ×angustilepidota Nakai, should be distin- We and Aizawa et al. (2018) also did not analyze guished from Q. mongolica var. mongolicoides the morphology of the southern Sakhalin popula- by the more or less dense stellate hairs on the ab- tions in which genetic admixture between axial surface of the leaves (Fig. S4 of Aizawa Q. mongolica var. crispula and Q. mongolica var. et al. 2008, Nagamitsu et al. 2019; Table 4) and mongolica was postulated. Further comparative cupules at least partly covered by elongate, linear studies of Q. mongolica from these regions is or subulate involucre scales with an acute apex, a needed to fully understand species delimitation distinct characteristic observed in cupules of June 2021 Aizawa & al. — New Name: Quercus mongolica var. mongolicoides 121

Q. dentata (Nakahara & Nishikawa 2009). Ledeb.; Nakai in Bot. Mag. (Tokyo) 29: 58 (1915), as “var. typica,” pro parte; Kitamura & Horikawa in Mem. Coll. Sci. Univ. Kyoto ser. B, 20: 22 Taxonomic Treatment (1951), as var. mongolica, pro parte; Ohwi, Fl. Jap.: 422 (1953), pro parte. Quercus mongolica Fisch. ex Ledeb. var. Quercus ×angustilepidota sensu Ohba in Sa- mongolicoides (H. Ohba) M. Aizawa, comb. take et al., Wild Flow. Jap. Woody Pl. 1: 70 (1989), nov. pro parte, non Nakai in Bot. Mag. (Tokyo) 31: 3 Basionym: Quercus serrata Murray subsp. mongoli- (1917), “anguste-lepidota.” coides H. Ohba in Fl. Japan (Iwatsuki et al. eds.) 2a: 49, in adnota (2006). —Quercus mongolicoides (H. Ohba) Japanese name. Fumoto-mizunara (Ohba Hiroki in J. Phytogeogr. Taxon. 64: 73 (2017). —Quercus 2006) crispula Blume var. mongolicoides (H. Ohba) Seriz. in Shidekobushi 1: 55 (2008). Typus. Japan, Aichi Pref., Seto city, Kaisho, 35°10′93″ Distribution. Japan. Kanto district (Tochigi N, 137°06′78″ E, 130 m alt., T. Miyazaki, 512004, 8 Dec. and Gunma prefectures) and Chubu district (Na- 2005, (Holo-, TI03125; Iso-, TI03127!). gano, Aichi, and Gifu prefectures). Details are Quercus mongolica auct. non Fisch. ex shown in Hiroki (2017).

Key to arborescent varieties of Quercus mongolica and an allied hybrid taxon.

1a. Leaf margin serrate with acute teeth ...... var. crispula 1b. Leaf margin crenate-dentate with rounded to widely obtuse teeth ...... 2 2a. Abaxial surface of leaves with more or less dense stellate hairs; involucral scales of cupule at least partly linear or subulate, apex acute ...... Q. ×angustilepidota 2b. Abaxial surface of leaves without or nearly without stellate hairs, involucral scales of cupule triangular-ovate, appressed and prominently humped, apex subacute to obtuse ...... 3 3a. Lateral veins of leaves (10–)13(–16); abaxial main vein glabrous or glabrescent ...... var. mongolicoides 3b. Lateral veins of leaves (6–)10(–12); abaxial main vein glabrescent or sparsely hairy ...... var. mongolica

Remarks: Quercus crispula var. horikawae is References variable in leaf shape (Noshiro 1984; Ohba 1989), but is well recognizable by its shrubby habit, bent Aizawa, M., K. Maekawa, H. Mochizuki, H. Saito, K. Harada, M. Kadomatsu, K. Iizuka & T. Ohkubo. trunk often decumbent near the ground and by 2018. Unveiling the origin of Quercus serrata subsp. smaller leaves (Ohba 2006). Its identity and no- mongolicoides found in Honshu, Japan, by using ge- menclature will be treated in another paper. netic and morphological analyses. Spec. Biol. 33: 174–190. Botany Section of Natural Environment Research Group of Tochigi Prefecture. 2003. Plants of Tochigi I; A Re- We would like to thank Dr. Takahide Kurosawa for help search of Natural Environments of Tochigi Prefec- with the taxonomic treatment. We also thank the prefec- ture. Davison of Natural Environment, Department tural forestry offices for permitting sampling, Dr. Ichiro of Forestry, Tochigi Prefecture, Utsunomiya (in Japa- Tamaki and Dr. Teruyoshi Nagamitsu for sharing infor- nese). mation on their Quercus studies, and Dr. Hiroshi Ikeda of Chen, J., Y. F. Zeng, W. J. Liao, P. C. Yan & J. G. Zhang. TI for permission to examine specimens. We acknowl- 2017. A novel set of single-copy nuclear gene markers edge the editor and anonymous reviewers for their valu- in white and implications for species delimita- able suggestions. tion. Genet. Genom. 13: 50. 122 Acta Phytotax. Geobot. Vol. 72

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Received June 2, 2020; accepted November 9, 2020

Appendix 1. Shape of leaf serrations (as proposed in Mochizuki et al. 2013) used in this study.