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阿兰岛上特有花楸类群的繁育系统与持续进化

Breeding systems and continuing evolution in the endemic Sorbus taxa on Arran.

作者信息

Robertson A, Newton A C, Ennos R A

机构信息

Institute of Ecology and Resource Management, University of Edinburgh, King's Buildings, Mayfield Rd, Edinburgh EH9 3JU, Scotland.

出版信息

Heredity (Edinb). 2004 Nov;93(5):487-95. doi: 10.1038/sj.hdy.6800528.

Abstract

The Arran whitebeams Sorbus arranensis and S. pseudofennica are two endemic woody plant taxa that have evolved on Arran through hybridisation. S. arranensis is a triploid hybrid between the widespread diploid S. aucuparia and the rare tetraploid S. rupicola. S. pseudofennica is a tetraploid formed by crossing between S. arranensis and S. aucuparia. In order to determine the mating systems of the two endemic species six maternal trees of each taxon together with 10-12 of their seed offspring were scored for their phenotype at three microsatellite loci and one nuclear intron locus. All seeds of S. arranensis were identical in phenotype to their maternal parents. In S. pseudofennica, 17.5% of all seeds differed in marker phenotype from their maternal parent. The proportion of seed with nonmaternal phenotypes varied significantly among maternal trees of S. pseudofennica. The results suggest that the triploid S. arranensis is an obligate apomict, whereas the tetraploid S. pseudofennica is a facultative apomict. Molecular marker analysis of three trees from Arran with an unusual leaf morphology indicates that they are the product of sexual reproduction by S. pseudofennica, and may originate from hybridisation with S. aucuparia. This research demonstrates that the Sorbus taxa on Arran are participants in an active evolutionary process generating novel biodiversity. Conservation programmes for these taxa should aim to preserve this evolutionary process rather than the individual taxonomic entities that it produces.

摘要

阿伦花楸(Sorbus arranensis)和拟芬氏花楸(S. pseudofennica)是两种在阿伦岛上通过杂交进化而来的地方性木本植物分类群。阿伦花楸是广泛分布的二倍体欧洲花楸(S. aucuparia)与罕见的四倍体岩生花楸(S. rupicola)之间的三倍体杂种。拟芬氏花楸是由阿伦花楸和欧洲花楸杂交形成的四倍体。为了确定这两个地方性物种的交配系统,对每个分类群的六棵母树及其10 - 12个种子后代在三个微卫星位点和一个核内含子位点的表型进行了评分。阿伦花楸的所有种子在表型上与其母本相同。在拟芬氏花楸中,17.5%的种子在标记表型上与其母本不同。具有非母本表型的种子比例在拟芬氏花楸的母树之间存在显著差异。结果表明,三倍体的阿伦花楸是专性无融合生殖体,而四倍体的拟芬氏花楸是兼性无融合生殖体。对阿伦岛上三棵具有异常叶形态的树进行的分子标记分析表明,它们是拟芬氏花楸有性繁殖的产物,可能起源于与欧洲花楸的杂交。这项研究表明,阿伦岛上的花楸分类群参与了一个产生新生物多样性的活跃进化过程。针对这些分类群的保护计划应旨在保护这一进化过程,而不是它所产生的个别分类实体。

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