Fruit evolution and adaptation to Mediterranean habitats in Raphanus (Brassicaceae)

人们普遍认为，过去环境条件的变化和全基因组的复制驱动了十字花科植物的辐射，产生了新的适应性形态和生理性状。在此，我们建议采用跨学科的方法来研究Raphanus属植物果实和一水硬膜结构的差异在空间扩散模式、发芽同步以及种群内和种群间遗传多样性模式方面的适应价值。Raphanus是一个地中海属，包括两个密切相关的异域野生一年生植物，R. raphanistrum和R. pugioniformis以及栽培R. sativus。前两种原产于东地中海，果实形态和传播能力不同，这表明单种子的raphanistrum和重多种子的pugioniformis在特定的栖息地是适应性的。因此，我们假设，在其原生地，长叶卷烟的长距离风传播可以解释其在相似的同质生境中的广泛分布，而短叶卷烟的短距离传播可以确保其在异质山地环境中留在安全的地点建立幼苗。因此，Raphanus提供了一个机会来研究和发展一个小属中果实结构和传播机制的进化过程模型。我们建议在以色列和巴勒斯坦地区对这两种野生物种进行详细的种群调查，包括种群内的空间安排、分布格局以及生物、地理和气候因素的评估。将在密闭场所测试长距离和短距离的扩散。此外，将研究果实和种子的形态和果实解剖，并对包在果皮中的种子和裸露的种子进行短期和长期发芽试验以及寿命试验。基于种群的阈值模型将用于解释环境对种子休眠/萌发的生态生理调节。在这方面，我们假设，长叶姜的萌发是在长时间吸胀的情况下发生的，而长叶姜的机械休眠是在微生物活动或磨损作用下分解果皮后才释放的。通过使用微卫星，我们还旨在了解生境和扩散策略的差异如何影响这些物种种群内部和种群之间的遗传变异。我们的项目结果将为一年生芸苔科植物的适应过程提供深入的见解，我们期望这项跨学科的研究将激励以色列和巴勒斯坦的学生加入这一研究领域。

It is widely accepted that past changes in environmental conditions plus whole-genome duplications have driven radiation of Brassicaceae, resulting in novel adaptive morphological and physiological traits. Here we suggest taking an interdisciplinary approach to investigate the adaptive value of the divergence in fruit and diaspore architecture in the genus Raphanus in respect to spatial dispersal patterns, germination synchronization, and patterns of genetic diversity within and among populations. Raphanus is a Mediterranean genus comprising two closely related allopatric wild annuals, R. raphanistrum and R. pugioniformis and the cultivated R. sativus. The first two are native to the East Mediterranean and differ in fruit morphology and dispersal ability, suggesting that single-seeded units of R. raphanistrum and the heavy multi-seeded diaspores of R. pugioniformis are adaptive in their specific habitats. Accordingly, we hypothesize that in their native range , long-distance wind dispersal in R. raphanistrum, can explain its wide distribution along similar homogenous habitats, while short- distance dispersal in R. pugioniformis ensures remaining in safe sites for seedling establishment in heterogeneous mountainous environments. Thus, Raphanus provides an opportunity to investigate and develop a model of evolutionary processes in fruit architecture and dispersal mechanisms in a small genus. We suggest conducting a detailed population survey of each of the two wild species in Israel and the Palestinian Authority, e.g. spatial arrangements within populations, distribution patterns , and assessment of biotic, edaphic and climatic factors. Dispersal over long and short distances will be tested in confined sites. Furthermore, fruit and seed morphology, and fruit anatomy will be investigated, and short- and long- term germination trials, as well as longevity tests will be set on seeds enclosed in the pericarp vs. bare seeds. Population-based threshold models will be used to explain eco-physiological regulation of seed dormancy /germination by the environment. In this respect we hypothesize that germination of R. raphanistrum occurs upon long imbibition, while pericarp-mediated mechanical dormancy of R. pugioniformis is released only after decomposition of the pericarp by microbial activity or abrasion. With the use of microsatellites we aim also to understand how the differences in habitat and dispersal strategy affect genetic variation within and among populations of these species. The results of our project will provide insight into adaptive processes in annual Brassicaceae and we expect that this interdisciplinary study will stimulate Israeli and Palestinian students to join this research area.