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Evidence for asymmetrical hybridization despite pre- and post-pollination reproductive barriers between two Silene species

View Article: PubMed Central - PubMed

ABSTRACT

Co-flowering species may undergo interspecific hybridization if they are closely related and share pollinators. However, a series of reproductive barriers between species can prevent interspecific gene flow, making natural hybridization a transient, rare event. Both morphological and molecular data indicated putative natural hybrids between two Silene species from southwest China, with pollen from S. yunnanensis fertilizing ovules of S. asclepiadae. Zhang et al. found that pollen production and viability were significantly lower in putative hybrids than the parental species. The low fecundity of the hybrids and other reproductive barriers between the two species could contribute to species fidelity.

No MeSH data available.


Flowers and a shared bumblebee pollinator of the two Silene species and a putative hybrid. An apical and side view of S. yunnanensis(A, D), hybrid (B, E) and S. asclepiadea(C, F) flower; and Bombus festivus sucking nectar from flowers of the three taxa (G–I), respectively. Minimum scale at second row = 1 mm.
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plw032-F1: Flowers and a shared bumblebee pollinator of the two Silene species and a putative hybrid. An apical and side view of S. yunnanensis(A, D), hybrid (B, E) and S. asclepiadea(C, F) flower; and Bombus festivus sucking nectar from flowers of the three taxa (G–I), respectively. Minimum scale at second row = 1 mm.

Mentions: The study was conducted in a university field station, Shangri-La Alpine Botanical Garden (SABG, 27°54′ N, 99°38′ E) of Yunnan Province, southwest China (see Fang and Huang 2013). The two studied species, S.asclepiadea Franchet and S.yunnanensis Franchet, are closely related within the ‘Cucubaloideae’ group (Zhou et al. 2001). Both species are perennial herbs that co-occur naturally in open alpine meadows mixed with shrubs and near the forest edges in the study site. Geographic ranges overlap, with S.yunnanensis reported from northwest Yunnan Province and S.aspclediadea from Yunnan and two neighboring provinces (eFloras 2008). The two species are protandrous, primarily distinguished by the flower and fruit morphology. Flowers of S. yunnanensis are pink with narrow, long, calyx tubes; its petal-limb length (the portion of the petal above the fused calyx) is much greater than that of S. asclepiadea, which has flowers with dark pink petals and short, broad calyx tubes (Fig. 1). S.asclepiadea flowers earlier (early July) than S. yunnanensis (middle July), but their flowering periods overlap several weeks in SABG, permitting potential interspecific hybridization. Fruit diameters of S. asclepiadea are broader than S. yunnanensis. Dozens of flowering individuals each of the two species were observed in one 50 m × 50 m meadow, suggesting that the population densities of both species were high.Figure 1.


Evidence for asymmetrical hybridization despite pre- and post-pollination reproductive barriers between two Silene species
Flowers and a shared bumblebee pollinator of the two Silene species and a putative hybrid. An apical and side view of S. yunnanensis(A, D), hybrid (B, E) and S. asclepiadea(C, F) flower; and Bombus festivus sucking nectar from flowers of the three taxa (G–I), respectively. Minimum scale at second row = 1 mm.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4940505&req=5

plw032-F1: Flowers and a shared bumblebee pollinator of the two Silene species and a putative hybrid. An apical and side view of S. yunnanensis(A, D), hybrid (B, E) and S. asclepiadea(C, F) flower; and Bombus festivus sucking nectar from flowers of the three taxa (G–I), respectively. Minimum scale at second row = 1 mm.
Mentions: The study was conducted in a university field station, Shangri-La Alpine Botanical Garden (SABG, 27°54′ N, 99°38′ E) of Yunnan Province, southwest China (see Fang and Huang 2013). The two studied species, S.asclepiadea Franchet and S.yunnanensis Franchet, are closely related within the ‘Cucubaloideae’ group (Zhou et al. 2001). Both species are perennial herbs that co-occur naturally in open alpine meadows mixed with shrubs and near the forest edges in the study site. Geographic ranges overlap, with S.yunnanensis reported from northwest Yunnan Province and S.aspclediadea from Yunnan and two neighboring provinces (eFloras 2008). The two species are protandrous, primarily distinguished by the flower and fruit morphology. Flowers of S. yunnanensis are pink with narrow, long, calyx tubes; its petal-limb length (the portion of the petal above the fused calyx) is much greater than that of S. asclepiadea, which has flowers with dark pink petals and short, broad calyx tubes (Fig. 1). S.asclepiadea flowers earlier (early July) than S. yunnanensis (middle July), but their flowering periods overlap several weeks in SABG, permitting potential interspecific hybridization. Fruit diameters of S. asclepiadea are broader than S. yunnanensis. Dozens of flowering individuals each of the two species were observed in one 50 m × 50 m meadow, suggesting that the population densities of both species were high.Figure 1.

View Article: PubMed Central - PubMed

ABSTRACT

Co-flowering species may undergo interspecific hybridization if they are closely related and share pollinators. However, a series of reproductive barriers between species can prevent interspecific gene flow, making natural hybridization a transient, rare event. Both morphological and molecular data indicated putative natural hybrids between two Silene species from southwest China, with pollen from S. yunnanensis fertilizing ovules of S. asclepiadae. Zhang et al. found that pollen production and viability were significantly lower in putative hybrids than the parental species. The low fecundity of the hybrids and other reproductive barriers between the two species could contribute to species fidelity.

No MeSH data available.