New Research Results from China
New Research Results from China in 2019 (9)

No.Chao-Qun Li, Tian-Feng Lü, Meng-Qi Han, Yang Dong, Peng-Wei Li, Yan Liu, and Yin-Zheng Wang


Reversal versus specialization in floral morphological evolution in Petrocosmea (Gesneriaceae) & some new taxa of Petrocosmea


Journal of Systematics and Evolution: Accepted Article

ORCID iD: 0000-0002-3113-2650




A widely held hypothesis in evolution is that adaptive specialization constrains the potential direction of future evolutionary change and thus may be irreversible, i.e., the Dollo’s law. However, this hypothesis has long been subject to debate in evolutionary biology. Floral specialization is intriguing as it is usually linked to reproductive isolation and may affect speciation. Here, following the discovery of four new taxa, we observed some interesting phenomena of reversal versus specialization in morphology in a clade with the most specialized flowers in the genus Petrocosmea. In the phylogenetic tree based on sequences of multiple DNA regions, the morphological reversals, especially the regain of a long corolla-tube, are nested within the branches characteristic of normally specialized flowers with short corolla tube and highly specialized zygomorphy. Our results demonstrate that the highly specialized floral organ of this clade is still actively evolving in multiple branches toward specialization while reversals to different ancestral states occur in some branches. The great disturbance of ecological environment is likely a crucial factor affecting trait reversibility, such as the rapid uplift of the Himalaya-Tibet plateau. The four new taxa are treated herein taxonomically. The flowers of this clade represent an interesting model to explore the genetic basis underlying the evolutionary reversal versus specialization and the interplay between genetic factors and environmental variables.

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Fig. 1. The most parsimonious tree and photos of flowers of corresponding taxa.The most parsimonious tree (left) is generated from combined cpDNA and nuclear DNA data. Photos of flowers are the corresponding taxa (bold faces indicate the new taxa) sampled in the phylogenetic analysis (right). Bootstrap (BS) values are on the left side of the slash and Bayesian posterior probabilities (PP) on the right. 1-2, outgroups, 1, Raphiocarpus petelotii, 2, R. begoniifolius3-6, species of clade A, 3-4, P. grandifolia, face (3) and lateral (4) view, 5-6, P. menglianensis, face (5) and lateral (6) view; 7-10, species of clade B, 7-8, P. sichuanensis, face (7) and lateral (8) view, 9-10, P. intraglabra, face (9) and lateral (10) view; 11-38, species of clade C, including four new taxa, 11-12, P.huanjiangensis, face (11) and lateral (12) view, 13-14, P. xingyiensis, face (13) and lateral (14) view, 15-16, P. shilinensis, face (15) and lateral (16) view, 17-18, new variety P. shilinensis var. changhuensis, face (17) and lateral (18) view, 19-20, P. minor, face (19) and lateral (20) view. 21-22, new species P. purpureoglandulosa, face (21) and lateral (22) view, 23-24, P. iodioides, face (23) and lateral (24) view, 25-26, P. leiandra, face (25) and lateral (26) view, 27-28, new species P. longituba, face (27) and lateral (28) view, 29-30, new species P. qionglaiensis, face (29) and lateral (30) view, 31-32, P. martinii, face (31) and lateral (32) view, 33-34, P. sericea, face (33) and lateral (34) view, 35-36, P. yanshanensis, face (35) and lateral (36) view, 37-38, P. grandiflora, face (37) and lateral (38) view; 39-42, species of clade D, 39-40, P. barbata, face (39) and lateral (40) view, 41-42, P. cavaleriei, face (41) and lateral (42) view; 43-46, species of clade E, 43-44, P. oblata, face (43) and lateral (44) view, 45-46, sinensis, face (45) and lateral (46) view. (15-16 Photos taken by Shui YM)




Fig. 2. Photos of P. shilinensis var. changhuensis with comparison of P. shilinensis. 1-7. P. shilinensis var. changhuensis. 1. Habitat. 2, 3. Plants with basal leaves. 4. Flower of face view, showing two white oblong stripes extended to the throat on abaxial corolla lip. 5. Flower of side view. 6. Stamen, showing filaments white. 7. Leaf, showing leaf rhombic, margin crenate, base cuneate, lateral veins abaxially conspicuous. 8-11. P. shilinensis. 8. Flower of face view, showing several white stripes on the inner surface of abaxial side of corolla restricted in the tube. 9. Flower of side view. 10. Stamen, showing filaments purple. 11. Leaf, showing leaf cordate, base cordate, margin serrulate, lateral veins abaxially unconspicuous. (8-11. Photos taken by Shui YM.)





Fig. 3. Photos of P. purpureoglandulosa with comparison of P. minor. 1-6. P. purpureoglandulosa. 1. Habitat. 2. Plants with basal leaves. 3. Flower of face view. 4. Flower of side view, showing the carinate-plicate structure straight on the adaxial side. 5. Abaxial corolla lip, showing lateral lobs broad ovate and two little round brown spots on the inner surface of corolla tube below filaments. 6. Stamen, showing filaments slightly curved, densely purple glandular. 7-11. P. minor. 7. Plants with basal leaves. 8. Flower of face view. 9. Flower of side view, showing the carinate-plicate structure protuberance on the adaxial side. 10. Abaxial corolla lip, showing lateral lobes triangular and two big triangular brown spots on the inner surface of corolla tube below filaments. 11. Stamen, showing filaments strongly geniculate, densely white glandular.



Fig. 4. Photos of P. qionglaiensis, P. longituba with comparison of P. iodioides and P. leiandra. 1-4. P. qionglaiensis. 1, 2. Habitat, growing on the moist shady cliff of the limestone hill. 3, 4. Plants with basal leaves. 5-8. P. longituba. 5, 6. Habitat, growing on the moist shady cliff of the limestone hill. 7, 8. Plants with basal leaves. 9-13. P. iodioides. 9. Face view. 10. Top view. 11. Side view. 12. Stamen. 13. Leaf. 14-18. P. leiandra. 14. Face view. 15. Top view. 16. Side view. 17. Stamen. 18. Leaf. 19-23. P. longituba. 19. Face view. 20. Top view. 21. Side view. 22. Stamen. 23. Leaf. 24-28. P. qionglaiensis. 24. Face view. 25. Top view. 26. Side view. 27. Stamen. 28. Leaf, showing petiole dark red-brown.




Fig. 5. Tube length divergence in Petrocosmea. X-axis: species of Petrocosmea; Y-axis: relative tube length (R (tube)). Line of 30% on Y axis was set to better shown the difference between species with long tube and short tube. 30% is the average value of relative tube length (R (tube)).