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25 August 2017, Volume 39 Issue 04
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  • Articles
    Origins and evolution of plant diversity in the Hengduan Mountains, China
    Hang Sun, Jianwen Zhang, Tao Deng, David E. Boufford
    2017, 39(04):  161-166.  doi:10.1016/j.pld.2017.09.004
    Abstract ( 9 )   HTML ( )   PDF (369KB) ( 1 )   Save
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    Spatio-temporal evolution of Allium L. in the Qinghai-Tibet-Plateau region:Immigration and in situ radiation
    Frank Hauenschild, Adrien Favre, Jan Schnitzler, Ingo Michalak, Martin Freiberg, Alexandra N. Muellner-Riehl
    2017, 39(04):  167-179.  doi:10.1016/j.pld.2017.05.010
    Abstract ( 14 )   HTML ( )   PDF (8661KB) ( 1 )   Save
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    A plethora of studies investigating the origin and evolution of diverse mountain taxa has assumed a causal link between geological processes (orogenesis) and a biological response (diversification). Yet, a substantial delay (up to 30 Myr) between the start of orogenesis and diversification is often observed. Evolutionary biologists should therefore identify alternative drivers of diversification and maintenance of biodiversity in mountain systems. Using phylogenetic, biogeographic, and diversification rate analyses, we could identify two independent processes that most likely explain the diversity of the widespread genus Allium in the QinghaieTibet Plateau (QTP) region:(1) While the QTP-related taxa of the subgenus Melanocrommyum diversified in situ, (2) QTP-related taxa of other subgenera migrated into the QTP from multiple source areas. Furthermore, shifts in diversification rates within Allium could not be attributed spatially and temporally to the uplift history of the QTP region. Instead, global cooling and climate oscillations in the Quaternary were major contributors to increased speciation rates in three clades of Allium. Our study therefore adds to the growing evidence supporting the "mountain-geo-biodiversity hypothesis", which highlights the role of climate oscillations for the diversification of mountain organisms.
    Seed dormancy and germination characteristics of two Rheum species in the Himalaya-Hengduan Mountains
    Deli Peng, Zhe Chen, Xiaojian Hu, Zhimin Li, Bo Song, Hang Sun
    2017, 39(04):  180-186.  doi:10.1016/j.pld.2017.05.009
    Abstract ( 13 )   HTML ( )   PDF (1118KB) ( 2 )   Save
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    Seed dormancy and germination characteristics are important factors determining plant reproductive success, and may be expected to have a major influence on plant distribution. In this study, we aimed to explore the characteristics of seed dormancy and germination in two endemic Rheum species (Rheum nobile and Rheum alexandrae) in the Himalaya-Hengduan Mountains. To determine the type of dormancy, fresh seeds of the two species (one population each) were incubated in light at 25/15 and 15/5℃, and then dry after-ripening (DAR) seeds were incubated on water agar substrate with or without GA3. To determine the effect of temperature and light on germination, DAR seeds of the two species (two populations each) were incubated both in the light and in the dark at several temperatures, including constant and alternating temperatures. Base temperature (Tb) and thermal times for 50% germination (θ50) were calculated. DAR released physiological dormancy (PD), increasing final germination at 15/5℃ and widening the range of germination temperatures from higher to lower, indicative of type 2 non-deep PD for the two Rheum species. Light had no significant effect on germination of seeds from the two species (two populations each). Seeds of the two species germinated significantly better (>80%) at medium temperatures (10-25℃) than at extreme low (5℃) or high (35℃) temperatures. Alternating temperatures (25/15 and 15/5℃) did not significantly increase the final germination of the two species either in the light and in the dark, but it promoted seed germination more quickly than corresponding constant temperatures in the light in both Rh. alexandrae populations, especially at 15/5℃. Germination in response to temperature was well described by the thermal-time model at suboptimal temperatures. The estimated Tb values were 1 and 0.9℃, respectively, in two Rh. nobile populations; 4 and 4.1℃, respectively, in two Rh. alexandrae populations; θ50 (thermal time) were 100 and 125 Cd, respectively in two Rh. nobile populations; 76.92 and 83.33 Cd, respectively in two Rh. alexandrae populations. The dormancy type, and germination responses to temperature and light condition does not explain why the two Rheum species are distributed in contrasting habitats. However, these findings reflect an advantageous germination strategy of these two Rheum species to adapt to the same alpine environments.
    Function of male and hermaphroditic flowers and size-dependent gender diphasy of Lloydia oxycarpa (Liliaceae) from Hengduan Mountains
    Yang Niu, Qiangbang Gong, Deli Peng, Hang Sun, Zhimin Li
    2017, 39(04):  187-193.  doi:10.1016/j.pld.2017.06.001
    Abstract ( 7 )   HTML ( )   PDF (1366KB) ( 1 )   Save
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    Although hermaphroditism is common in flowering plants, unisexual flowers occur in many plant taxa, forming various sexual systems. However, the sexual system of some plants is difficult to determine morphologically, given that their sex expression may be influenced by both genetic and environmental factors. Specifically, androdioecy (the coexistence of both male and hermaphroditic individuals in the same population) has often been confused with the gender diphasy, a gender strategy in which plants change their sex expression between seasons. We studied the reproductive function of male and hermaphroditic flowers of Lloydia oxycarpa (Liliaceae), in order to investigate its sexual system and determine whether it is a gender-diphasic species. We found that although male flowers occur in a considerable number of plants, relative to hermaphrodites, they did not exhibit any significant reproductive advantage in terms of flower size, pollen quantity, attractiveness to visitors or siring success. In addition, this plant has spontaneous self-pollination and showed no inbreeding depression. These results render the maintenance of male individuals almost impossible. Furthermore, a considerable number of individuals changed their sex in successive years. The sex expression was found to be related to bulb size and dry weight, with larger individuals producing hermaphroditic flowers and smaller individuals producing male flowers. These results suggest that L. oxycarpa is not an androdioecious plant but represents a rare case of size-dependent gender diphasy.
    Karyotypes of nineteen species of Asteraceae in the Hengduan Mountains and adjacent regions
    Wenguang Sun, Xiangguang Ma, Jianwen Zhang, Fuming Su, Yonghong Zhang, Zhimin Li
    2017, 39(04):  194-201.  doi:10.1016/j.pld.2017.08.001
    Abstract ( 7 )   HTML ( )   PDF (4172KB) ( 1 )   Save
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    The Hengduan Mountains region is a biodiversity hotspot. In this study, we report the karyotypes of 19 species (21 populations) of Asteraceae from this region, 14 of which are reported for the first time. We also examined polyploidy in Asteraceae plants and summarized karyotype data in the literature for 69 congeneric taxa. In these genera, there were five different ploidy levels in the region, though the most dominant was diploid (73.08%). There is no direct evidence that ploidy level and karyotype asymmetry are associated with the distribution of recorded Asteraceae species from the Hengduan Mountains. This suggests that polyploidy (26.92%) may not play an important role in the evolutionary history of these plants, even though, among these genera, the ratio of paleopolyploidy was high (46.15%).
    Natural selection on floral traits of Caltha scaposa (Ranunculaceae), an alpine perennial with generalized pollination system from Northwest Yunnan
    Guopeng Zhang, Lihua Meng, Zhikun Wu, Zhiqiang Zhang, Lingjuan Yin, Yongping Yang, Yuanwen Duan
    2017, 39(04):  202-207.  doi:10.1016/j.pld.2017.03.001
    Abstract ( 6 )   HTML ( )   PDF (2446KB) ( 3 )   Save
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    Floral traits, including those invisible to humans but visible to pollinators, that increase pollination efficiency may be selected by pollinators in plant species with pollen limitation of seed production, but the importance of pollinators as selective agents on different floral traits needs to be further quantified experimentally. In the present study, we examined selective strength on flower diameter, flower height, UV bulls-eye size, sepal size and UV proportion via female fitness in Caltha scaposa, based on openpollinated and hand-pollinated flowers, through which pollinator-mediated selection was calculated for each of floral traits. Our results suggest that seed production of C. scaposa is pollen limited in natural conditions. There was directional selection (△βbpollinator=-0.12) for larger flowers in open-pollinated flowers, while no significant selection was found in flower height, UV bulls-eye size, sepal size or UV proportion. Statistically significant selection was found in UV bulls-eye size, sepal size and UV proportion in hand-pollinated flowers, but interactions with pollinators contributed only to flower diameter. We conclude that in C. scaposa, floral traits that are subjected to selection might be driven by multiple selective agents, and suggest the importance of investigating floral traits that are invisible to human but visible to pollinators in measuring pollinator-mediated selection via male fitness.
    Heavy collecting induces smaller and deeper Fritillariae Cirrhosae Bulbus in the wild
    Xinhui Li, Lin Liu, Xu Gu, Jianying Xiang
    2017, 39(04):  208-213.  doi:10.1016/j.pld.2017.05.002
    Abstract ( 4 )   HTML ( )   PDF (1419KB) ( 1 )   Save
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    Fritillariae Cirrhosae Bulbus is a well-known traditional Chine medicinal herb. However, the demand for this herb is leading to over-collection and its decline in the wild. This study aims to investigate the ecological conditions of Fritillaria cirrhosa under the influence of human disturbance, biotic species interactions and climatic conditions. We established a total of 78 plots at 14 sites of F. cirrhosa in its distribution center, the Hengduan Mountains area. At each site, we estimated the abundance of F. cirrhosa at different distances from roads. The diameter and height of F. cirrhosa fruit and bulbs were measured and compared to underground bulb depth. We then analyzed the effects of environmental conditions and human disturbance on the abundance of F. cirrhosa using variance partitioning. We found that (1) abundance of F. cirrhosa and their underground bulb depth showed a significant linear increase with the distance from the main road; (2) the diameter/height of fruits and the diameter/height of fruits/bulbs showed significantly different responses to the human disturbance; (3) the community associates, climate and spatial conditions can explain 58%, 22% and 27%, respectively, of the variance in the F. cirrhosa abundance. These results highlight the fact that human disturbance and biotic factors have a great influence on the survival of F. cirrhosa, even more than climate conditions.
    Bidirectional natural hybridization between sympatric Ligularia vellerea and L. subspicata
    Huai Ning, Jiaojun Yu, Xun Gong
    2017, 39(04):  214-220.  doi:10.1016/j.pld.2017.07.001
    Abstract ( 5 )   HTML ( )   PDF (717KB) ( 3 )   Save
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    Natural hybridization has been regarded as a crucial pathway of speciation and provides the raw materials for the evolution of biodiversity. The interspecific natural hybridization of the genus Ligularia Cass. is universal and has been considered to be an important factor driving the high diversity of Ligularia species in the Hengduan Mountains, China. Although the natural hybridization between L. vellerea and L. subspicata was reported previously, the direction of hybridization was uncertain due to the limitation of sampling. Thus, in this study, we sampled more individuals and increased two fragments of chloroplast DNA on the basis of the previous study to further verify the natural hybridization between L. vellerea and L. subspicata and confirm the direction of hybridization. Based on DNA sequences (atpBrbcL, trnL-rpl32, trnQ-5'rps16, and nuclear ribosomal internal transcribed spacer region) data, we concluded that putative hybrids were primary products of hybridization between L. vellerea and L. subspicata and the hybridization was bidirectional. Moreover, sympatric L. tongolensis was not apparently involved in the hybridization. Surprisingly, some pure L. subspicata individuals showed the disaccordance between morphology and DNA data, which might indicate that introgression occurs between L. vellerea and L. subspicata.
    How cushion communities are maintained in alpine ecosystems:A review and case study on alpine cushion plant reproduction
    Jianguo Chen, Yanbo Li, Yang Yang, Hang Sun
    2017, 39(04):  221-228.  doi:10.1016/j.pld.2017.07.002
    Abstract ( 9 )   HTML ( )   PDF (2374KB) ( 0 )   Save
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    Cushion species occur in nearly all alpine environments worldwide. In past decades, the adaptive and ecosystem-engineering roles of such highly specialized life forms have been well studied. However, the adaptive strategies responsible for cushion species reproductive success and maintenance in severe alpine habitats remain largely unclear. In this study, we reviewed the current understanding of reproductive strategies and population persistence in alpine cushion species. We then present a preliminary case study on the sexual reproduction of Arenaria polytrichoides (Caryophyllaceae), a typical cushion species inhabiting high elevations of the Himalaya Hengduan Mountains, which is a hotspot for diversification of cushion species. Finally, we highlight the limitations of our current understanding of alpine cushion species reproduction and propose future directions for study.
    Primula pengzhouensis (Primulaceae), a new species from Sichuan, southwestern China
    Yuan Xu, Gehan Huang, Chiming Hu, Gang Hao
    2017, 39(04):  229-231.  doi:10.1016/j.pld.2017.08.003
    Abstract ( 4 )   HTML ( )   PDF (3645KB) ( 3 )   Save
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    A new species, Primula pengzhouensis (Primulaceae), from central Sichuan, China, is described and illustrated. It is assigned to Primula sect. Aleuritia subsect. Yunnanensis, and is most similar to P. socialis, but can be easily distinguished from that species by its much larger flower and elliptic or ovate-elliptic leaves.