Table S1Plant materials, herbarium vouchers and GenBank accession numbers in this study.

Species / Vouchers / GenBank accession No.
ITS / trnK-matK / rbcL / ycf5
D. chrysanthum / HITBC 106786 / AF362047 / AF447070 / JF713156 / FJ216684
D. chrysotoxum / HITBC 058292 / AF362023 / AF448862 / JF713157 / FJ216692
D. crepidatum / HITBC 109998 / AY842035 / AF447071 / JF713162 / FJ216685
D. crumenatum / Sunmei 201105 / AF521608 / JF713166
D. crystallinum / HITBC 058282 / GU339116 / AF445447 / FJ216564 / EU553970
D.cucullatum / HITBC 064558 / FJ428219 / AF447068 / HM055077 / FJ216688
D. denneanum / HITBC 078079 / AF521606 / GU181387 / GQ435641
D. fimbriatum / HITBC 127048 / AY842036 / AF448863 / JF713178 / FJ216677
D. gibsonii / Sunmei 201112 / GU339105 / FJ216551 / FJ216679
D. henryi / HITBC 050894 / EF629323
D. jenkinsii / HITBC 138875 / EF629321 / GU906226 / JF713186 / FJ216689
D. loddigesii / HITBC 058304 / EU592016 / AF448864 / JF949999 / EU553976
D. longicornu / HITBC 140935 / GU339112
D. moniliforme / HITBC 131218 / GU339111 / FJ216568 / EU553973
D. nobile / HITBC 139978 / AF311781 / AF445448 / HM055130 / FJ216678
D. pendulum / Sunmei 201106 / GU339115 / GU991358 / FJ216555 / EU553965
D. polyanthum / HITBC 107390 / AF362913 / AF445450 / HM055142 / EU553969
D. salaccense / Sunmei 201102 / AF362026 / AF445451
D. thyrsiflorum / HITBC 110009 / FJ384733 / KF143728 / HM055145 / FJ216676

Table S2 Altitudes and original habitats of the 19 Dendrobium species considered in this study.

Species / Code / Altitude / Groups / Habitats
D. chrysanthum Wallich ex Lindley / chrysa / 700-2500 / Group3 / Tree trunks in dense broad-leaved forests, lithophytic on wet rocks in valleys
D. chrysotoxum Lindley / chryso / 500-1600 / Group2 / Tree trunks or lithophytic on rocks in sparse evergreen broad-leaved forests
D. crepidatum Lindley & Paxton / crep / 1000-1800 / Group3 / Tree trunks in evergreen broad-leaved forests, lithophytic on rocks in mountain valleys
D. crumenatum Swartz / crum / 10-800 / Group1 / Tree trunks in hill slopes in sparse evergreen broad-leaved forests or along road
D. crystallinum H. G. Reichenbach / crys / 500-1700 / Group2 / Tree trunks at forest margins or in sparse evergreen broad-leaved forests
D. cucullatum R. Brown / cucu / 400-1500 / Group1 / Tree trunks in sparse evergreen broad-leaved forests, lithophytic on rocks in mountain valleys
D. denneanum Kerr / denn / 600-2500 / Group2 / Tree trunks in sparse evergreen broad-leaved forests
D. fimbriatum Hooker / fimb / 600-1700 / Group3 / Tree trunks in dense evergreen broad-leaved forests, lithophytic on damp rocks in mountain valleys
D. gibsonii Lindley / gibs / 800-1000 / Group1 / Tree trunks in sparse evergreen broad-leaved forests
D. henryi Schlechter / henr / 600-1700 / Group3 / Tree trunks in mountain forests, lithophytic on damp rocks in mountain valleys
D. jenkinsii Wallich ex Lindley / jenk / 700-1300 / Group1 / Tree trunks in sparse evergreen broad-leaved forests
D. loddigesii Rolfe / lodd / 400-1500 / Group1 / Tree trunks in mountain forests, lithophytic on rocks in forests
D. longicornu Lindley / long / 1200-2500 / Group2 / Tree trunks in mountain forests
D. moniliforme (Linnaeus) Swartz / moni / 600-3000 / Group2 / Tree trunks in evergreen broad-leaved forests, lithophytic on rocks in forests and cliffs
D. nobile Lindley / nobi / 500-1700 / Group3 / Tree trunks in mountain forests, lithophytic on rocks in mountain valleys
D. pendulum Roxburgh / pend / 1000-1600 / Group2 / Tree trunks in sparse evergreen broad-leaved forests
D. polyanthum Wallich ex Lindley / poly / 700-1800 / Group2 / Tree trunks in sparse evergreen broad-leaved forests
D. salaccense (Blume) Lindley / sala / 600-1000 / Group1 / Tree trunks in forests, lithophytic on rocks in sparse evergreen broad-leaved forests
D. thyrsiflorum H. G. Reichenbach ex André / thyr / 1100-1800 / Group2 / Tree trunks in mountain forests

Table S3 Sample size (individual plant numbers / leaf numbers) and values for leaf traits in the 19 Dendrobium species.

Species / Sample size / LA / LD / RWC / VD / LT / UCT / UET / LET / SD / SA / SI
D. chrysanthum / 6/16 / 33.2 / 120 / 97.5 / 2.20 / 255 / 1.45 / 37.5 / 19.2 / 49.6 / 898 / 8.88
D. chrysotoxum / 10/37 / 45.8 / 213 / 95.4 / 2.57 / 583 / 4.32 / 26.7 / 18.8 / 64.0 / 692 / 7.39
D. crepidatum / 10/38 / 22.2 / 75.8 / 95.5 / 1.83 / 335 / 1.49 / 35.7 / 21.9 / 55.7 / 793 / 8.35
D. crumenatum / 6/18 / 14.8 / 67.1 / 84.7 / 7.01 / 785 / 2.83 / 18.9 / 12.5 / 57.7 / 609 / 7.23
D. crystallinum / 6/12 / 23.6 / 105 / 94.9 / 5.27 / 274 / 1.61 / 57.7 / 23.2 / 76.1 / 781 / 10.3
D.cucullatum / 10/50 / 14.2 / 52.7 / 97.5 / 1.67 / 609 / 1.27 / 33.8 / 41.6 / 24.2 / 631 / 5.92
D.denneanum / 6/12 / 24.7 / 158 / 96.5 / 1.58 / 339 / 2.49 / 33.4 / 15.9 / 52.9 / 701 / 5.31
D. fimbriatum / 10/50 / 23.0 / 206 / 97.5 / 2.78 / 253 / 2.28 / 47.0 / 23.7 / 51.1 / 644 / 7.24
D. gibsonii / 6/24 / 17.9 / 184 / 96.4 / 3.64 / 247 / 1.64 / 49.5 / 26.0 / 53.7 / 788 / 6.48
D. henryi / 6/13 / 13.0 / 130 / 94.4 / 1.36 / 374 / 1.13 / 47.0 / 30.3 / 42.3 / 760 / 9.13
D. jenkinsii / 7/38 / 3.31 / 123 / 97.9 / 2.01 / 1105 / 6.11 / 25.4 / 14.7 / 86.3 / 388 / 7.94
D. loddigesii / 6/25 / 3.05 / 49.6 / 96.2 / 2.02 / 586 / 1.79 / 39.4 / 26.3 / 25.8 / 676 / 6.11
D. longicornu / 6/12 / 4.05 / 164 / 90.3 / 1.67 / 506 / 2.50 / 27.2 / 14.2 / 61.0 / 961 / 8.13
D. moniliforme / 6/12 / 1.93 / 133 / 95.6 / 3.75 / 286 / 2.16 / 29.2 / 19.3 / 113 / 640 / 11.3
D. nobile / 6/12 / 28.1 / 106 / 95.8 / 2.03 / 536 / 2.31 / 52.8 / 36.2 / 37.8 / 1222 / 12.4
D. pendulum / 6/12 / 22.9 / 93.1 / 91.5 / 2.20 / 432 / 1.50 / 57.4 / 33.4 / 43.1 / 1226 / 10.7
D.polyanthum / 10/31 / 26.1 / 54.4 / 96.6 / 1.62 / 669 / 1.22 / 40.1 / 31.4 / 30.8 / 795 / 9.06
D. salaccense / 6/12 / 9.16 / 209 / 97.3 / 3.93 / 251 / 3.55 / 13.8 / 9.77 / 177 / 263 / 8.04
D. thyrsiflorum / 6/12 / 48.3 / 141 / 97.6 / 1.22 / 498 / 2.85 / 29.0 / 16.2 / 57.2 / 698 / 6.89

LA, leaf area (cm2); LD, leaf density (kg m-3); RWC, relative water content (%); VD, vein density (mm mm-2); LT, leaf thickness (μm); UCT, upper cuticle thickness (μm); UET, upper epidermal thickness (μm); LET, lower epidermal thickness (μm); SD, stomatal density (no. mm-2); SA, stomatal area (μm²); SI, stomatal index (%).