Turchetto Caroline, Lima Jacqueline S, Rodrigues Daniele M, Bonatto Sandro L, Freitas Loreta B
Laboratory of Molecular Evolution, Department of Genetics, Universidade Federal do Rio Grande do Sul, PO Box 15053, Porto Alegre, Brazil, Laboratory of Genetic Diversity, Universidade Federal de Goiás, PO Box 131, 74001-970 Goiania, GO, Brazil and Laboratory of Genomic and Molecular Biology, Pontifícia Universidade Católica do Rio Grande do Sul, Ipiranga 6681, 90610-001 Porto Alegre, RS, Brazil.
Laboratory of Molecular Evolution, Department of Genetics, Universidade Federal do Rio Grande do Sul, PO Box 15053, Porto Alegre, Brazil, Laboratory of Genetic Diversity, Universidade Federal de Goiás, PO Box 131, 74001-970 Goiania, GO, Brazil and Laboratory of Genomic and Molecular Biology, Pontifícia Universidade Católica do Rio Grande do Sul, Ipiranga 6681, 90610-001 Porto Alegre, RS, Brazil
Ann Bot. 2015 May;115(6):939-48. doi: 10.1093/aob/mcv025. Epub 2015 Mar 25.
The evolution of selfing is one of the most common transitions in flowering plants, and this change in mating pattern has important systematic and ecological consequences because it often initiates reproductive isolation and speciation. Petunia axillaris (Solanaceae) includes three allopatric subspecies widely distributed in temperate South America that present different degrees of self-compatibity and incompatibility. One of these subspecies is co-distributed with P. exserta in a restricted area and presents a complex, not well-understood mating system. Artificial crossing experiments suggest a complex system of mating in this sympatric area. The main aims of this study were to estimate the pollen dispersal distance and to evaluate the breeding structure of P. axillaris subsp. axillaris, a hawkmoth-pollinated taxon from this sympatric zone.
Pollen dispersal distance was compared with nearest-neighbours distance, and the differentiation in the pollen pool among mother plants was estimated. In addition, the correlation between genetic differentiation and spatial distance among plants was tested. All adult individuals (252) within a space of 2800 m(2) and 15 open-pollinated progeny (285 seedlings) were analysed. Genetic analyses were based on 12 polymorphic microsatellite loci.
A high proportion of self-pollination was found, indicating a mixed-mating system. The maximum pollen dispersal distance was 1013 m, but most pollination events (96 %) occurred at a distance of 0 m, predominantly in an inbreeding system. Both parents among sampled individuals could be identifed in 60-85 % of the progeny.
The results show that most pollen dispersal in the hawkmoth-pollinated P. axillaris subsp. axillaris occurs within populations and there is a high proportion of inbreeding. This mating system appears to favour species integrity in a secondary contact zone with the congener species P. exserta.
自花授粉的演化是开花植物中最常见的转变之一，这种交配模式的变化具有重要的系统发育和生态后果，因为它常常引发生殖隔离和物种形成。腋花矮牵牛（茄科）包括三个异域分布的亚种，广泛分布于南美洲温带地区，呈现出不同程度的自交亲和性和不亲和性。其中一个亚种与外露矮牵牛在一个有限区域内共同分布，呈现出一个复杂的、尚未完全理解的交配系统。人工杂交实验表明，在这个同域分布区域存在一个复杂的交配系统。本研究的主要目的是估计花粉传播距离，并评估腋花矮牵牛亚种腋花矮牵牛的繁殖结构，该亚种是来自这个同域分布区的一种天蛾传粉类群。
将花粉传播距离与最近邻距离进行比较，并估计母株间花粉库的差异。此外，还测试了植物间遗传分化与空间距离之间的相关性。对2800平方米空间内的所有成年个体（252株）和15个开放授粉后代（285株幼苗）进行了分析。遗传分析基于12个多态性微卫星位点。
发现自花授粉比例很高，表明存在混合交配系统。最大花粉传播距离为1013米，但大多数授粉事件（96%）发生在0米的距离，主要是在近亲繁殖系统中。在60 - 85%的后代中可以鉴定出抽样个体的双亲。
结果表明，在天蛾传粉的腋花矮牵牛亚种腋花矮牵牛中，大多数花粉传播发生在种群内，近亲繁殖比例很高。这种交配系统似乎有利于在与同属物种外露矮牵牛的次生接触区保持物种完整性。
