Breeding system and spatial isolation from congeners strongly constrain seed set in an insect-pollinated apomictic tree: Sorbus subcuneata (Rosaceae).
Breeding system and spatial isolation from congeners strongly constrain seed set in an insect-pollinated apomictic tree: Sorbus subcuneata (Rosaceae).
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DOI：
10.1038/srep45122
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发表时间：
2017-03-24
影响因子：
4.6
通讯作者：
Cresswell JE
中科院分区：
文献类型：
--
作者：
Hamston TJ;Wilson RJ;de Vere N;Rich TC;Stevens JR;Cresswell JE
在植物中，无融合生殖通过种子产生克隆后代，并能为孤立的个体提供生殖保证。然而，许多无融合生殖需要授粉来发育功能性胚乳才能成功结实(假配子)，因此存在授粉受限的风险，特别是在需要异种花粉的自交不亲和物种中。我们使用微卫星亲子关系分析和人工授粉来研究亚楔花杉的花粉限制，这是一种受威胁的特有树木，与其同系物S.admonitor共生。我们证实，亚楔形花序是一种专性假配子无融合生殖，但开放授粉的花很少产生种子(花到种子的转化率 <； 为1%)，尽管它们在柱头上迅速积累花粉。人工异种授粉可获得较高的花籽转化率(65%)，然而，我们估计自由授粉的自花授粉与异种授粉的比例至少为22：1。尽管异种授粉有效，但随着父本树和母本树的空间分离，沙枣树对自由授粉花种子父性的贡献迅速下降。因此，旨在通过这种繁育系统维持物种的保护努力必须同时管理同种生物，这也将保持罕见的异种受精的潜力，这通常会导致这些谱系的快速多样化。
In plants, apomixis results in the production of clonal offspring via seed and can provide reproductive assurance for isolated individuals. However, many apomicts require pollination to develop functional endosperm for successful seed set (pseudogamy) and therefore risk pollination-limitation, particularly in self-incompatible species that require heterospecific pollen. We used microsatellite paternity analysis and hand pollinations to investigate pollen-limitation in Sorbus subcuneata, a threatened endemic tree that co-occurs with its congener, S. admonitor. We confirmed that S. subcuneata is an obligate pseudogamous apomict, but open-pollinated flowers rarely produced seed (flower-to-seed conversion < 1%) even though they rapidly accumulated pollen on their stigmas. Manual heterospecific pollination by S. admonitor resulted in a high flower-to-seed conversion rate (65%), however, we estimate that the ratio of self: heterospecific pollination in open-pollinated flowers was at least 22:1. Despite the efficacy of heterospecific pollination, the contribution of S. admonitor trees to paternity in seed from open-pollinated flowers of S. subcuneata decreased rapidly with the spatial separation between paternal and maternal trees. Conservation efforts aimed at maintaining species with this breeding system must therefore manage the congeners in tandem which will also maintain the potential for rare heterospecific fertilisation that typically cause rapid diversification in these lineages.