J Plant Ecol ›› 2016, Vol. 9 ›› Issue (2): 224-232.doi: 10.1093/jpe/rtv049

• Research Articles • Previous Articles     Next Articles

Shortened anther-stigma distance reduces compatible pollination in two distylous Primula species

Shu-Juan Liu1, Ling-Yun Wu1, and Shuang-Quan Huang2,*   

  1. 1 State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, No. 299 Bayi Road, Wuchang District, Wuhan 430072, China; 2 School of Life Sciences, Central China Normal University, 152 Luoyu Avenue, Hongshan District, Wuhan 430079, China
  • Received:2015-05-21 Accepted:2015-06-13 Online:2015-06-24 Published:2016-03-24
  • Contact: Huang, Shuang-Quan E-mail:hsq@mail.ccnu.edu.cn

Abstract: Aims Distyly has been regarded as an adaptation to improve compatible pollination between two floral morphs with reciprocal herkogamy. The hypothesis that the different positions of anthers and stigmas within flowers as well as their reciprocal position between morphs, reduce the probability of self pollination raised by Darwin has been rarely tested. In this study, we measured stigmatic pollen loads in response to reduced reciprocal herkogamy in two Primula species.
Methods To see whether reciprocal herkogamy can increase compatible and/or reduce incompatible pollen deposition, thus promoting compatible pollination, we shortened the distance between anthers and stigmas within the flowers by changing the position of the corolla tube, to which the anthers were fused, i.e. reduced herkogamy in natural populations of Primula secundiflora and P. poissonii and quantified stigmatic pollen loads in the field over 2 years.
Important findings In both species, stigmatic pollen loads were significantly higher in the long-styled (L-morph) than in the short-styled morph (S-morph) in both control and manipulated flowers, but percentage of compatible pollen in S-morph were higher. Flowers manipulated to halve the anther–stigma distance showed a similar pattern for 2 years: total pollen grain counts on stigmas did not differ significantly but compatible pollen grains in L- and S-morphs were significantly decreased in both species. The percentage of compatible pollen loads was decreased by 68.7% in P. secundiflora and 65.3% in P. poissonii in L-morphs, while it decreased by 30.6% and 2.9% in S-morphs, respectively. Our manipulation of the relative position of anthers and stigmas in the two distylous species indicated that a lower degree of herkogamy reduced compatible but incompatible pollen transfer was likely to increase. The higher proportion of compatible pollen in the S-morph than in the L-morph in the two Primula species could be attributed to the accessibility of two-level sexual organs, floral orientations and pollinator behaviors. This is a first attempt to manipulate intraflower herkogamy for understanding adaptation of heterostyly, shedding insights into how the reciprocal herkogamy promotes compatible pollination.

Key words: distyly, compatible pollination, floral trait, Primula, reciprocal herkogamy, stigmatic pollen load

摘要:
Aims Distyly has been regarded as an adaptation to improve compatible pollination between two floral morphs with reciprocal herkogamy. The hypothesis that the different positions of anthers and stigmas within flowers as well as their reciprocal position between morphs, reduce the probability of self pollination raised by Darwin has been rarely tested. In this study, we measured stigmatic pollen loads in response to reduced reciprocal herkogamy in two Primula species.
Methods To see whether reciprocal herkogamy can increase compatible and/or reduce incompatible pollen deposition, thus promoting compatible pollination, we shortened the distance between anthers and stigmas within the flowers by changing the position of the corolla tube, to which the anthers were fused, i.e. reduced herkogamy in natural populations of Primula secundiflora and P. poissonii and quantified stigmatic pollen loads in the field over 2 years.
Important findings In both species, stigmatic pollen loads were significantly higher in the long-styled (L-morph) than in the short-styled morph (S-morph) in both control and manipulated flowers, but percentage of compatible pollen in S-morph were higher. Flowers manipulated to halve the anther–stigma distance showed a similar pattern for 2 years: total pollen grain counts on stigmas did not differ significantly but compatible pollen grains in L- and S-morphs were significantly decreased in both species. The percentage of compatible pollen loads was decreased by 68.7% in P. secundiflora and 65.3% in P. poissonii in L-morphs, while it decreased by 30.6% and 2.9% in S-morphs, respectively. Our manipulation of the relative position of anthers and stigmas in the two distylous species indicated that a lower degree of herkogamy reduced compatible but incompatible pollen transfer was likely to increase. The higher proportion of compatible pollen in the S-morph than in the L-morph in the two Primula species could be attributed to the accessibility of two-level sexual organs, floral orientations and pollinator behaviors. This is a first attempt to manipulate intraflower herkogamy for understanding adaptation of heterostyly, shedding insights into how the reciprocal herkogamy promotes compatible pollination.

[1] Xiao-Yue Wang, Qiu-Mei Quan, Bo Wang, Yun-Xiang Li, Shuang-Quan Huang. Discovery of androecium color polymorphism in Epimedium pubescens with habitat preference of anther/pollen color in the genus [J]. J Plant Ecol, 2018, 11(4): 533-541.
[2] Xian-Feng Jiang, Xing-Fu Zhu, Ling-Ling Chen, Qing-Jun Li. What ecological factors favor the shift from distyly to homostyly? A study from the perspective of reproductive assurance [J]. J Plant Ecol, 2018, 11(4): 645-655.
[3] Roderick W. Bouman, Sandy-Lynn Steenhuisen, Timotheüs van der Niet. The role of the pollination niche in community assembly of Erica species in a biodiversity hotspot [J]. J Plant Ecol, 2017, 10(4): 634-648.
[4] Hai-Dong Li, Yan-Hui Zhao, Zong-Xin Ren, Zhi-Kun Wu, Lorne M. Wolfe, Peter Bernhardt, Hong Wang. Fitness-related selection on floral traits in the distylous plant Primula poissonii (Primulaceae) [J]. J Plant Ecol, 2017, 10(3): 559-568.
[5] Ai-Qin Zhang, Shuang He, Ya-Xin Zhai, Shuang-Quan Huang. Does persistence of showy calyces in Limonium leptolobum enhance pollinator attraction? [J]. J Plant Ecol, 2015, 8(2): 182-186.
[6] Nicholas A. Barber, Nicole L. Soper Gorden. How do belowground organisms influence plant-pollinator interactions? [J]. J Plant Ecol, 2015, 8(1): 1-11.
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