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The reproductive strategy of a pollinator-limited Himalayan plant, Incarvillea mairei (Bignoniaceae).

Ai H, Zhou W, Xu K, Wang H, Li D - BMC Plant Biol. (2013)

Bottom Line: Here, we investigated the mating system and pollination of Incarvillea mairei, a perennial Himalayan herb typically found at altitudes between 3000 and 4500 m.Its main effective pollinator was Halictus sp., and visitation frequency was low.The increased floral longevity and high pollination efficiency operated as compensatory mechanisms to counteract low pollinator visitation frequency.

View Article: PubMed Central - HTML - PubMed

Affiliation: Key Laboratory for Plant Biodiversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China. wanghong@mail.kib.ac.cn.

ABSTRACT

Background: Plants may adapt to alpine habitats by specialization in the reproductive strategy and functional aspects of their flowers and pollination systems. Alpine habitats reduce the opportunities for cross-pollination in a relatively high proportion of alpine plant species, and self-pollination may be favored in these adverse conditions. Here, we investigated the mating system and pollination of Incarvillea mairei, a perennial Himalayan herb typically found at altitudes between 3000 and 4500 m.

Results: Analyses of floral morphology, observation of plant-pollinator interactions, and hand pollination experiments were conducted in three natural populations. Outcrossing rates and effective numbers of pollen donors were assessed in 45 open-pollinated families by using progeny analysis based on seven microsatellite markers. Incarvillea mairei displayed a set of apparently specialized floral traits, the stigma is sensitive to touch and close immediately and its reopening allows a second opportunity for the receipt of pollen. The species is fully self-compatible but employs a predominantly outcrossing mating system according to parentage analysis (tm > 0.9). Fruit set was low (26.3%), whereas seed set was high (67.2%), indicating that this species suffers pollinator limitation. Its main effective pollinator was Halictus sp., and visitation frequency was low.

Conclusions: Floral features such as having a sensitive stigma and anther-prongs, in conjunction with pollinator behavior, function together contributing to a set of unique reproductive adaptations that enhance outcrossing success. The increased floral longevity and high pollination efficiency operated as compensatory mechanisms to counteract low pollinator visitation frequency.

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Flower structures of Incarvillea mairei and pollinator behavior. (A) Rocky meadow habitat of population GML. (B) Mature flower. (C)The large, bilobed sensitive stigma and four anthers. (D) Longitudinal section of flower. (E) Anther appendages (attached oppositely to each lobe). (F) Opened stigma. (G) Closed Stigma. (H) Halictid bee touching the stigma. (I) Halictid bee is pressing the anther-thorns (arrow indicating released pollen). (J) Halictid bee exiting flower. (K) After bee has exited, the stigma remained closed. a.i: inner anther; a.o: outer anther; t.o: outer anther-thorn; t.i: inner anther-thorn; s: slit in anther-lobe; p: pad.
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Figure 1: Flower structures of Incarvillea mairei and pollinator behavior. (A) Rocky meadow habitat of population GML. (B) Mature flower. (C)The large, bilobed sensitive stigma and four anthers. (D) Longitudinal section of flower. (E) Anther appendages (attached oppositely to each lobe). (F) Opened stigma. (G) Closed Stigma. (H) Halictid bee touching the stigma. (I) Halictid bee is pressing the anther-thorns (arrow indicating released pollen). (J) Halictid bee exiting flower. (K) After bee has exited, the stigma remained closed. a.i: inner anther; a.o: outer anther; t.o: outer anther-thorn; t.i: inner anther-thorn; s: slit in anther-lobe; p: pad.

Mentions: Incarvillea mairei mainly grows on rocky, grassy slopes and meadows (Figure 1A). Flowering occurs in early spring after snowmelt. This plant is a stemless perennial herb with two to five pairs of leaflets. The inflorescences are racemose, and individual plants produce one to four flowers. Flowers are showy and each possesses a large, sensitive stigma composed of two lobes positioned in front of the anthers (Figures 1B-D). The four stamens are didynamous and epipetalous, with anthers pressed closely against the style (Figures 1C and D). Each anther bears two stiff prongs in opposing directions, one on each lobe, connected to a protuberant pad (Figure 1D and E). The two lobes of the stigma begin to open following the initiation of anthesis (Figure 1F) and close immediately following detection of touch stimuli (Figure 1G).


The reproductive strategy of a pollinator-limited Himalayan plant, Incarvillea mairei (Bignoniaceae).

Ai H, Zhou W, Xu K, Wang H, Li D - BMC Plant Biol. (2013)

Flower structures of Incarvillea mairei and pollinator behavior. (A) Rocky meadow habitat of population GML. (B) Mature flower. (C)The large, bilobed sensitive stigma and four anthers. (D) Longitudinal section of flower. (E) Anther appendages (attached oppositely to each lobe). (F) Opened stigma. (G) Closed Stigma. (H) Halictid bee touching the stigma. (I) Halictid bee is pressing the anther-thorns (arrow indicating released pollen). (J) Halictid bee exiting flower. (K) After bee has exited, the stigma remained closed. a.i: inner anther; a.o: outer anther; t.o: outer anther-thorn; t.i: inner anther-thorn; s: slit in anther-lobe; p: pad.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4219382&req=5

Figure 1: Flower structures of Incarvillea mairei and pollinator behavior. (A) Rocky meadow habitat of population GML. (B) Mature flower. (C)The large, bilobed sensitive stigma and four anthers. (D) Longitudinal section of flower. (E) Anther appendages (attached oppositely to each lobe). (F) Opened stigma. (G) Closed Stigma. (H) Halictid bee touching the stigma. (I) Halictid bee is pressing the anther-thorns (arrow indicating released pollen). (J) Halictid bee exiting flower. (K) After bee has exited, the stigma remained closed. a.i: inner anther; a.o: outer anther; t.o: outer anther-thorn; t.i: inner anther-thorn; s: slit in anther-lobe; p: pad.
Mentions: Incarvillea mairei mainly grows on rocky, grassy slopes and meadows (Figure 1A). Flowering occurs in early spring after snowmelt. This plant is a stemless perennial herb with two to five pairs of leaflets. The inflorescences are racemose, and individual plants produce one to four flowers. Flowers are showy and each possesses a large, sensitive stigma composed of two lobes positioned in front of the anthers (Figures 1B-D). The four stamens are didynamous and epipetalous, with anthers pressed closely against the style (Figures 1C and D). Each anther bears two stiff prongs in opposing directions, one on each lobe, connected to a protuberant pad (Figure 1D and E). The two lobes of the stigma begin to open following the initiation of anthesis (Figure 1F) and close immediately following detection of touch stimuli (Figure 1G).

Bottom Line: Here, we investigated the mating system and pollination of Incarvillea mairei, a perennial Himalayan herb typically found at altitudes between 3000 and 4500 m.Its main effective pollinator was Halictus sp., and visitation frequency was low.The increased floral longevity and high pollination efficiency operated as compensatory mechanisms to counteract low pollinator visitation frequency.

View Article: PubMed Central - HTML - PubMed

Affiliation: Key Laboratory for Plant Biodiversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China. wanghong@mail.kib.ac.cn.

ABSTRACT

Background: Plants may adapt to alpine habitats by specialization in the reproductive strategy and functional aspects of their flowers and pollination systems. Alpine habitats reduce the opportunities for cross-pollination in a relatively high proportion of alpine plant species, and self-pollination may be favored in these adverse conditions. Here, we investigated the mating system and pollination of Incarvillea mairei, a perennial Himalayan herb typically found at altitudes between 3000 and 4500 m.

Results: Analyses of floral morphology, observation of plant-pollinator interactions, and hand pollination experiments were conducted in three natural populations. Outcrossing rates and effective numbers of pollen donors were assessed in 45 open-pollinated families by using progeny analysis based on seven microsatellite markers. Incarvillea mairei displayed a set of apparently specialized floral traits, the stigma is sensitive to touch and close immediately and its reopening allows a second opportunity for the receipt of pollen. The species is fully self-compatible but employs a predominantly outcrossing mating system according to parentage analysis (tm > 0.9). Fruit set was low (26.3%), whereas seed set was high (67.2%), indicating that this species suffers pollinator limitation. Its main effective pollinator was Halictus sp., and visitation frequency was low.

Conclusions: Floral features such as having a sensitive stigma and anther-prongs, in conjunction with pollinator behavior, function together contributing to a set of unique reproductive adaptations that enhance outcrossing success. The increased floral longevity and high pollination efficiency operated as compensatory mechanisms to counteract low pollinator visitation frequency.

Show MeSH
Related in: MedlinePlus