Pollination ecology of alpine herb Meconopsis integrifolia at different altitudes

doi:10.17521/cjpe.2015.0001

Abstract

Abstract: Aims

We studied the breeding system and pollination ecology of Meconopsis integrifolia (Papaveraceae), which is an alpine herb, for two consecutive years.

Methods

Five plots (plot 1, 4452 m a.s.l; plot 2, 4215 m a.s.l; plot 3, 4081 m a.s.l; plot 4, 3841 m a.s.l; plot 5, 3681 m a.s.l) were established along an altitudinal gradient in the Balang Mountain. Flower longevity, stigma height and the highest stamen were measured and recorded. The stigma receptivity and pollen viability were tested by the Benzidine-H₂O₂ method and the TTC method, respectively. The breeding system was tested by experimental approaches, and flower visitors were observed over the life span of the flower. The temperatures of the flower and environment were also recorded. Important findings Flower longevity was greater in plots 1 and 2 than in plots 3, 4 and 5. The stigmas were higher than the anthers at the beginning of anthesis, and the distance between stigmas and the anthers then gradually decreased with the progress of flowing. The stigmas and anthers came into contact when the corolla wilted in 65% of the flowers sampled, indicating an incomplete herkogamy. The stigmas became receptive before the dehiscence of anthers (protogyny). Under natural conditions, stigma receptivity lasted for 8 d and pollen viability lasted for 2 d. Hand-pollination experiments indicated that M. integrifolia was self-compatible and did not exhibit apomixis. Seed set was significantly increased after a supplemental hand-pollination, suggesting the pollen-limitation of reproduction. The pollinators in plots 1 and 2 were flies, and in plots 3, 4 and 5 flies and Thripidae spp. We observed that flies moved and transferred pollen between plants, and that both flies and Thripidae spp. moved within flowers, the latter resulted in “facilitated selfing”. About 65% of the plants sampled set seed by autonomous self-pollination. There was a significant difference in the visiting frequency of flies between plots, with plot 1 being the lowest and plot 2 the highest. Pollen limitations were evident across all plots due to lack of sufficient outcrossing pollinators. Two different selfing mechanisms, unexplored here, may provide a partial compensation for the natural reproduction of this alpine species in the arid, alpine habitats. M. integrifolia could attract pollinators by providing a warm shelter.

http://jtp.cnki.net/bilingual/detail/html/ZWSB201501001

Key words: dichogamy, “greenhouse plant”, herkogamy, Meconopsis integrifolia, pollen limitation, reproductive assurance, reproductive strategy

WU Yun, LIU Yu-Rong, PENG Han, YANG Yong, LIU Guang-Li, CAO Guo-Xing, ZHANG Qiang. Pollination ecology of alpine herb Meconopsis integrifolia at different altitudes[J]. Chin J Plant Ecol, 2015, 39(1): 1-13.

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Figures/Tables 8

References 66

1	Anderson B, Midgley JJ, Stewart BA (2003). Facilitated selfing offers reproductive assurance: A mutualism between a hemipteran and carnivorous plant. American Journal of Botany, 90, 1009-1015.
2	Arroyo MTK, Armesto JJ, Primack RB (1985). Community studies in pollination ecology in the high temperate Andes of central Chile. II. Effect of temperature on visitation rates and pollination possibilities. Plant Systematics and Evolution, 149, 187-203.
3	Arroyo MTK, Muñoz MS, Henríquez C, Till-Bottraud I, Pérez F (2006). Erratic pollination, high selfing levels and their correlates and consequences in an attitudinally widespread above-tree-line species in the high Andes of Chile. Acta Oecologica, 30, 248-257.
4	Arroyo MTK, Primack R, Armesto J (1982). Community studies in pollination ecology in the high temperate Andes of central Chile. I. Pollination mechanisms and altitudinal variation. American Journal of Botany, 69, 82-97.
5	Bergman P, Molar U, Holmgren B (1996). Micrometeorological impacts on insect activity and plant reproductive success in an alpine environment, Swedish Lapland. Arctic and Alpine Research, 28, 196-202.
6	Bingham RA, Orthner AR (1998). Efficient pollination of alpine plants. Nature, 391, 238-239.
7	Blionis GJ, Vokou D (2001). Pollination ecology of Campanula species on Mt Olympos, Greece. Ecography, 24, 287-297.
8	Blionis GJ, Vokou D (2002). Structural and functional divergence of Campanula spatulata subspecies on Mt Olympos (Greece). Plant Systematics and Evolution, 232, 89-105.
9	Busch JW (2005). The evolution of self-compatibility in geographically peripheral populations of Leavenworthia alabamica (Brassicaceae). American Journal of Botany, 92, 1503-1512.
10	Chuang H (1981). The systematic evolution and the geographical distribution of Meconopsis vig. Acta Botanica Yunnanica, 3, 139-146.
	(in Chinese with English abstract) [庄璇 (1981). 绿绒蒿属的系统演化及地理分布. 云南植物研究,3, 139-146.]
11	Clark MJ, Husband BC (2007). Plasticity and timing of flower closure in response to pollination in Chamerion angustifolium (Onagraceae). International Journal of Plant Science, 168, 619-625.
12	Dafni A (1992). Pollination Ecology: A Practical Approach. Oxford University Press, Oxford. 1-57.
13	Dar AR, Zafar R, Dar GH (2010). Reproductive ecology of an endemic angiosperm, Meconopsis latifolia Prain (Papaveraceae), in the Kashmir Himalaya, India. Journal of Biological Science, 10, 490-498.
14	Devoto MD, Medan D, Montaldo NH (2005). Patterns of interaction between plants and pollinators along an environmental gradient. Oikos, 109, 461-472.
15	Duan YW, He YP, Zhang TF, Liu JQ (2007a). Delayed selfing in an alpine species Gentianopsis barbata. Journal of Plant Ecology (Chinese Version), 31, 110-117.
	(in Chinese with English abstract) [段元文, 何亚平, 张挺峰, 刘建全 (2007a). 高山植物扁蕾的延迟自交机制. 植物生态学报, 31, 110-117.]
16	Duan YW, Zhang TF, Liu JQ (2007). Interannual fluctuations in floral longevity, pollinator visitation and pollination limitation of an alpine plant (Gentiana straminea Maxim., Gentianaceae) at two altitudes in the Qinghai-Tibetan Plateau. Plant Systematics and Evolution, 267, 255-265.
17	Duan YW, Zhang TF, Liu JQ (2007b). Pollination biology of Anisodus tanguticus (Solanaceae). Biodiversity Science, 15, 584-591.
	(in Chinese with English abstract) [段元文, 张挺峰, 刘建全 (2007b). 山莨菪(茄科)的传粉生物学. 生物多样性, 15, 584-591.]
18	Fabbro T, Körner C (2004). Altitudinal differences in flower traits and reproductive allocation. Flora, 199, 70-81.
19	Fishman MA, Hadany L (2013). Pollinators’ mating rendezvous and the evolution of floral advertisement. Journal of Theoretical Biology, 316, 99-106.
20	He HX (2006). Pollination Biology and Breeding System of the Endangered Chinese Endemic Kingdonia uniflora (Ranunculaceae). Master degree dissertation, Shaanxi Normal University, Xi’an. 12.
	(in Chinese with English abstract). [贺海霞 (2006). 濒危植物独叶草(毛茛科)的传粉生物学及繁育系统研究. 硕士论文, 陕西师范大学, 西安. 12.]
21	He YP, Liu JQ (2004). Pollination ecology of Gentiana straminea Maxim. (Gentianaceae), an alpine perennial in the Qinghai-Tibet Plateau. Acta Ecologica Sinica, 24, 215-220.
	(in Chinese with English abstract) [何亚平, 刘建全 (2004). 青藏高原高山植物麻花艽的传粉生态学研究. 生态学报, 24, 215-220.]
22	Heinrich B (1972). Energetics of temperature regulation and foraging in a bumblebee, Bombus terricola Kirby. Journal of Comparative Physiology, 77, 49-64.
23	Herlihy CR, Eckert CG (2005). Evolution of self-fertilization at geographical range margins? A comparison of demographic, floral, and mating system variables in central vs. peripheral populations of Aquilegia canadensis (Ranunculaceae). American Journal of Botany, 92, 744-751.
24	Hou QZ, Duan YW, Si QW, Yang HL (2009). Pollination ecology of Gentiana lawrencei var. Farreri, a late-flowering Qinghai-Tibet Plateau species. Chinese Journal of Plant Ecology, 33, 1156-1164.
	(in Chinese with English abstract) [侯勤正, 段元文, 司庆文, 杨慧玲 (2009). 青藏高原晚期开花植物线叶龙胆的传粉生态学. 植物生态学报, 33, 1156-1164.]
25	Ishii HS, Sakai S (2002). Temporal variation in floral display size and individual floral sex allocation in racemes of Narthecium asiaticum (Liliaceae). American Journal of Botany, 89, 441-446.
26	Makrodimos N, Blionis GJ, Krigas N, Vokou D (2008). Flower morphology, phenology and visitor patterns in an alpine community on Mt Olympos, Greece. Flora—Morphology, Distribution, Functional Ecology of Plants, 203, 449-468.
27	Mao ZB, Boehler C, Ge XJ (2011). Pollination ecology and breeding system of Impatiens lateristachys (Balsaminaceae) endemic to China. Guihaia, 31, 160-166.
	(in Chinese with abstract) [毛志斌, Boehler C, 葛学军 (2011). 侧穗凤仙花的传粉生态和繁育系统. 广西植物, 31, 160-166.]
28	Meng LH, Wang Y, Luo J, Liu CY, Yang YP, Duan YW (2012). Pollination ecology and its implication for conservation of an endangered perennial herb native to the East-Himalaya, Megacodon stylophorus (Gentianaceae). Plant Ecology and Evolution, 145, 356-362.
29	Meng Y, Xie HY, Nie ZL, Gu ZJ, Yang YP (2006). A karyomorphological study on four species of Meconopsis Vig. (Papaveraceae) from the Hengduan Mountains, SW China. Garyologia, 59, 1-6.
30	Mir BA, Koul S, Soodan AS (2013). Reproductive biology of Withania ashwagandha sp. Novo (Solanaceae). Industrial Crops and Products, 45, 442-446.
31	Pan CC, Liu LD, Zhao HL, Hou YL, Zhang L, Wang LJ (2012). Pollination biology of Elaeagnus angustifolia in the middle reaches of the Heihe River in Northwest China. Journal of Desert Research, 32, 780-783.
	(in Chinese with English abstract) [潘成臣, 刘林德, 赵哈林, 侯月利, 张莉, 王丽娟 (2012). 黑河中游沙枣的传粉生物学研究. 中国沙漠, 32, 780-783.]
32	Peng DL, Zhang ZQ, Niu Y, Yang Y, Song B, Sun H, Li ZM (2012). Advances in the studies of reproductive strategies of alpine plants. Biodiversity Science, 20, 286-299.
	(in Chinese with English abstract) [彭德力, 张志强, 牛洋, 杨扬, 宋波, 孙航, 李志敏 (2012). 高山植物繁殖策略的研究进展. 生物多样性, 20, 286-290.]
33	Pickering CM, Stock M (2004). Insect colour preference compared to flower colours in the Australian Alps. Nordic Journal of Botany, 23, 217-223.
34	Rader R, Edwards W, Westcott DA, Cunningham SA, Howlett BG (2013). Diurnal effectiveness of pollination by bees and flies in agricultural Brassica rapa: Implications for ecosystem resilience. Basic and Applied Ecology, 14, 20-27.
35	Ruan CJ, Qin P, Teixeira da Silva JA (2011). Relationship between reproductive assurance and mixed mating in perennial Kosteletzkya virginica. South African Journal of Botany, 77, 280-291.
36	Schoen DJ, Morgan MT, Bataillon T (1996). How does self-pollination evolve? Inferences from floral ecology and molecular genetic variation. Philosophical Transactions of the Royal Society of London (Series B), 351, 1281-1290.
37	Shang XY, Li C, Zhang CZ, Yang YC, Shi JG (2006). Non-alkaloid constituents from a Tibetan medicine Meconopsis quintuplinervia. China Journal of Chinese Materia Medica, 31, 468-471.
	(in Chinese with English abstract) [尚小雅, 李冲, 张承忠, 杨永春, 石建功 (2006). 藏药五脉绿绒蒿中非生物碱成分. 中国中药杂志, 31, 468-471.]
38	Shang XY, Wang YH, Li C, Zhang CZ, Yang YC, Shi JG (2006). Acetylated flavonol diglucosides from Meconopsis quintuplinervia. Phytochemistry, 67, 511-515.
39	Shao JW, Zhang XP, Zhang ZX, Zhu GP (2008). Identification of effective pollinators of Primula merrilliana and effects of flower density and population size on pollination efficiency. Journal of Systematics and Evolution, 46, 537-544.
	(in Chinese with English abstract) [邵剑文, 张小平, 张中信, 朱国萍 (2008). 安徽羽叶报春的有效传粉昆虫及花朵密度和种群大小对传粉效果的影响. 植物分类学报, 46, 537-544.]
40	Si QW, Hou QZ, Zhu XF, Zhou DW, Yang HL (2010). Pollination biology of Gentiana dahurica (Gentianaceae). Acta Botanica Boreali-Occidentalia Sinica, 30, 2433-2436.
	(in Chinese with English abstract) [司庆文, 侯勤正, 朱兴福, 周党卫, 杨慧玲 (2010). 达乌里秦艽的传粉生物学研究. 西北植物学报, 30, 2433-2436.]
41	Sieber Y, Holderegger R, Waser NM, Thomas VFD, Braun S, Erhardt A, Reyer HU, Wirth LR (2011). Do alpine plants facilitate each other’s pollination? Experiments at a small spatial scale. Acta Oecologica, 37, 369-374.
42	Singhal VK, Kumar P (2008). Impact of cytomixis on meiosis, pollen viability and pollen size in wild populations of Himalayan poppy (Meconopsis aculeate Royle). Journal of Bioscience, 33, 371-380.
43	Stanton ML, Galen C (1989). Consequences of flower heliotropism for reproduction in an alpine buttercup (Ranunculus adoneus). Oecologia, 78, 477-485.
44	Steinacher G, Wagner J (2010). Flower longevity and duration of pistil receptivity in high mountain plants. Flora— Morphology, Distribution, Functional Ecology of Plants, 205, 376-387.
45	Sulaiman IM, Babu CR (1996). Enzyme polymorphism analyses in three endangered species of Himalayan poppy, Meconopsis (Papaveraceae). Genetic Resources and Crop Evolution, 43, 351-356
46	Sun S, Cao GX, Luo YJ, Li QJ (2010). Maintenance and functional gender specialization of flexistyly. Chinese Journal of Plant Ecology, 34, 827-838.
	(in Chinese with English abstract) [孙杉, 操国兴, 罗燕江, 李庆军 (2010). 花柱卷曲性的维持及功能性别特化. 植物生态学报, 34, 827-838.]
47	Teixido AL, Méndez M, Valladares F (2011). Flower size and longevity influence florivory in the large-flowered shrub Cistus ladanifer. Acta Oecologica, 37, 418-421.
48	Tian JP, Liu KM, Hu GW (2004). Pollination ecology and pollination system of Impatiens reptans (Balsaminaceae) endemic to China. Annals of Botany, 93, 167-175.
49	Torres-Díaz C, Gómez-González S, Stotz GC, Torres-Morales P, Paredes B, Pérez-Millaqueo M, Gianoli E (2011). Extremely long-lived stigmas allow extended cross- pollination opportunities in a high Andean plant. PLoS ONE, 6, e19497.
50	Totland Ø (2001). Environment-dependent pollen limitation and selection on floral traits in an alpine species. Ecology, 82, 2233-2244.
51	Tsukaya H (2002). Optical and anatomical characteristics of bracts from the Chinese “glasshouse” plant, Rheum alexandrae Batalin (Ploygonaceae), in Yunnan, China. Journal of Plant Research, 115, 59-63.
52	Vesprini JL, Pacini E (2005). Temperature-dependent floral longevity in two Helleborus species. Plant Systematics and Evolution, 252, 63-70.
53	Vesprini JL, Pacini E (2010). Pollination ecology in sympatric winter flowering Helleborus (Ranunculaceae). Flora— Morphology, Distribution, Functional Ecology of Plants, 205, 627-632.
54	Wan JP, Zhu XF, Li QJ (2011). Breeding system of protogynous Mandragora caulescens (Solanaceae). Plant Diversity and Resources, 33, 565-570.
	(in Chinese with English abstract) [万金鹏, 朱兴福, 李庆军 (2011). 雌先熟植物茄参(茄科)的繁育系统. 植物分类与资源学报, 33, 565-570.]
55	Xiao LX (2009). The Pollination Biology of Four Species of Impatiens L. Master degree dissertation, Hunan Normal University, Changsha. 4.
	(in Chinese with English abstract). [肖乐希 (2009). 四种凤仙花属(Impatiens L.) 植物的传粉生物学研究. 硕士论文, 湖南师范大学, 长沙. 4.]
56	Xiao LX, Liu KM (2009). Floral traits and pollination system of Impatiens chinensis (Balsaminaceae). Bulletin of Botanical Research, 29, 164-168.
	(in Chinese with English abstract) [肖乐希, 刘克明 (2009). 华凤仙花部特征和传粉系统研究. 植物研究, 29, 164-168.]
57	Yang FS, Qin AL, Li YF, Wang XQ (2012). Great genetic differentiation among populations of Meconopsis integrifolia and its implication for plant speciation in the Qinghai- Tibetan Plateau. PLoS ONE, 7, e37196.
58	Ye YM, Zhang JW, Qi YC, Chen TH, Bao MZ (2007). Studies on stigma receptivity and pollen viability of Zinnia elegans. Scientia Agricultura Sincia, 40, 2376-2381.
	(in Chinese with English abstract) [叶要妹, 张俊卫, 齐迎春, 陈天花, 包满珠 (2007). 百日草柱头可授性和花粉生活力的研究. 中国农业科学, 40, 2376-2381.]
59	Zhang DY, Jiang XH (2001). Mating system evolution, resource allocation, and genetic diversity in plants. Acta Phytoecologica Sinica, 25, 130-143.
	(in Chinese with English abstract) [张大勇, 姜新华 (2001). 植物交配系统的进化、资源分配对策与遗传多样性. 植物生态学报, 25, 130-143.]
60	Zhang TF, Duan YW, Liu JQ (2006). Pollination ecology of Aconitum gymnandrum (Ranunculaceae) at two sites with different altitudes. Acta Phytotaxonomica Sinica, 44, 362-370.
	(in Chinese with English abstract) [张挺峰, 段元文, 刘建全 (2006). 露蕊乌头(毛茛科)不同海拔居群的传粉生态学. 植物分类学报, 44, 362-370.]
61	Zhang ZQ, Li QJ (2008). Autonomous selfing provides reproductive assurance in an alpine ginger Roscoea schneideriana (Zingiberaceae). Annals of Botany, 102, 531-538.
62	Zhang ZQ, Li QJ (2009). Review of evolutionary ecology of floral longevity. Chinese Journal of Plant Ecology, 33, 598-606.
	(in Chinese with English abstract) [张志强, 李庆军 (2009). 花寿命的进化生态学意义. 植物生态学报, 33, 598-606.]
63	Zhong YF, Zhang Z, Song XQ, Zhou ZD (2014). Pollination biology of Impatiens hainanensis (Balsaminaceae) populations at different altitudes. Biodiversity Science, 22, 467-475.
	(in Chinese with English abstract) [钟云芳, 张哲, 宋希强, 周兆德 (2014). 海南凤仙花不同海拔种群的传粉生物学. 生物多样性, 22, 467-475.]
64	Zhou Y, Song JZ, Choi FFK, Wu HF, Qiao CF, Ding LS, Gesang SL, Xu HX (2009). An experimental design approach using response surface techniques to obtain optimal liquid chromatography and mass spectrometry conditions to determine the alkaloids in Meconops species. Journal of Chromatography A, 1216, 7013-7023.
65	Zhu JH, Ou SJ, Mai FZ, He QG, Xu N, Peng HX (2006). Effect of flies on mango pollination and the relationship between their pollination activity and the temperature. Chinese Journal of Tropical Crops, 27(4), 5-8.
	(in Chinese with English abstract) [朱建华, 欧世金, 麦福珍, 何全光, 徐宁, 彭宏祥 (2006). 苍蝇对杧果的传粉作用及其与温度的关系. 热带作物学报, 27(4, 5-8.]
66	Zhu JH, Xu N, Wang ZY, Li HL, Lu GF, Li DB, Li GW, Huang FZ, Peng HX (2010). Study on the species of pollination insects of longan and the relationship between their pollination activity and temperature. Chinese Journal of Tropical Crops, 31, 646-650.
	(in Chinese with English abstract) [朱建华, 徐宁, 王助引, 李鸿莉, 陆贵锋, 李冬波, 黎光旺, 黄凤珠, 彭宏祥 (2010). 龙眼传粉昆虫种类及其传粉活动与温度的关系. 热带作物学报, 31, 646-650.]

样地 Plot	海拔高度 Elevation (m)	花寿命 Floral longevity (d)
1	4 452	15.81 ± 0.37 ^a
2	4 215	14.11 ± 0.46 ^b
3	4 081	13.03 ± 0.40 ^c
4	3 841	11.64 ± 0.26 ^d
5	3 681	12.61 ± 0.39 ^c

样地 Plot	海拔高度 Elevation (m)	花寿命 Floral longevity (d)
1	4 452	15.81 ± 0.37 ^a
2	4 215	14.11 ± 0.46 ^b
3	4 081	13.03 ± 0.40 ^c
4	3 841	11.64 ± 0.26 ^d
5	3 681	12.61 ± 0.39 ^c

样地 Plot	蕾期 Bud	开花后时间 Time after flowering (d)
样地 Plot	蕾期 Bud	1	2	3	4	5	6	7	8	9	10	11
1	-	+	++	+++	+++	++	++	+	+	+	-	-
2	-	+	++	+++	+++	++	++	+	+	+	-	-
3	-	+	++	+++	+++	+++	++	++	+	-	-	-
4	-	+	++	++	+++	+++	++	++	+	-	-	-
5	-	++	+++	+++	++	++	++	++	-	-	-	-

样地 Plot	蕾期 Bud	开花后时间 Time after flowering (d)
样地 Plot	蕾期 Bud	1	2	3	4	5	6	7	8	9	10	11
1	-	+	++	+++	+++	++	++	+	+	+	-	-
2	-	+	++	+++	+++	++	++	+	+	+	-	-
3	-	+	++	+++	+++	+++	++	++	+	-	-	-
4	-	+	++	++	+++	+++	++	++	+	-	-	-
5	-	++	+++	+++	++	++	++	++	-	-	-	-

处理 Treatment	样地1 Plot 1		样地2 Plot 2		样地3 Plot 3		样地4 Plot 4		样地5 Plot 5
处理 Treatment	结实率 Seed set rate (%)	坐果率 Fruit set rate (%)	结实率 Seed set rate (%)	坐果率 Fruit set rate (%)	结实率 Seed set rate (%)	坐果率 Fruit set rate (%)	结实率 Seed set rate (%)	坐果率 Fruit set rate (%)	结实率 Seed set rate (%)	坐果率 Fruit set rate (%)
对照 Control	34.5 ± 2.44^b (n = 20)	60.0	37.8 ± 5.43^b (n = 20)	75.0	50.4 ± 5.42^a (n = 20)	65.0	52.4 ± 7.65^b (n = 18).	60.0	49.8 ± 2.73^b (n = 20)	65.0
去雄不套网 Emasculation without netting	27.8 ± 4.98^b (n = 20)	50.0	31.3 ± 5.94^b (n = 18)	45.0	28.0 ± 11.82^b (n = 20)	60.0	32.1 ± 7.06^c (n = 20)	42.1	30.7 ± 0.50^c (n = 20)	65.0
套网 Netting without emasculation	15.8 ± 3.95^c (n = 19)	30.0	17.7 ± 6.42^c (n = 20)	45.0	20.4 ± 4.37^b (n = 20)	40.0	25.4 ± 4.78^c (n = 19)	35.0	19.5 ± 3.31^d (n = 20)	35.0
人工自交 Manual selfing	41.9 ± 3.11^a (n = 20)	55.0	50.1 ± 6.84^a (n = 20)	60.0	52.5 ± 4.35^a (n = 20)	65.0	58.2 ± 4.56^b (n = 16)	68.75	59.1 ± 2.26^b (n = 19)	63.2
人工异交 Manual outcrossing	55.1 ± 10.01^a (n = 19)	70.0	66.2 ± 5.30^a (n = 20)	85.0	64.3 ± 4.79^a (n = 20)	85.0	76.2 ± 2.18^a (n = 19)	75.0	71.5 ± 2.47^a (n = 20)	80.0