目的:岩石露头植被分布在世界各地,并拥有在恶劣环境条件下进化的多样化和独特的植物区系。不幸的是,这种生态系统中的种子生态学很少受到关注,特别是关于种子性状,发芽对非生物因素的反应以及系统发育相关性对这些特征的潜在作用,我们提供了巴西岩石露头植被的种子功能生态学的第一个定量和系统发育信息合成,特别关注石英石和铁石坎波卢比。
方法:使用功能特征数据数据库,我们计算了371个分类群的七个种子性状的系统发育信号,并测试了它们是否在生长形式之间变化,地理分布,和微栖息地。我们还进行了荟萃分析,包括102个分类单元的4,252个发芽记录,以评估光的影响。温度,以及与火有关的camporupestre物种发芽的线索,并探索了上述生态群和种子性状如何调节发芽反应。
结果:所有性状和发芽反应均显示中等至强烈的系统发育信号。Camporupestre物种对光有积极的反应,并且在20-25ºC之间有最大的发芽。超过这个范围的温度的影响被生长形式所缓和,物种地理分布,和微生境。暴露于80°C以上的热休克的种子失去了生存能力,但是烟雾加速了发芽。我们发现了种子质量对光和热冲击的调节作用,更大的,休眠的种子对热的耐受性更好,但对光的敏感性较低。在土壤水分利用率增加的时期,来自干燥栖息地的物种进化了物候策略以同步发芽。
结论:系统发育相关性在巴西岩石露头植被的种子生态形成中起着重要作用。然而,种子性状和发芽反应在生长形式之间差异显著,物种地理分布和微生境,为再生生态位假说和功能性状在这些生态系统中形成发芽的作用提供支持。
OBJECTIVE: Rock outcrop vegetation is distributed worldwide and hosts a diverse and unique flora that evolved under harsh environmental conditions. Unfortunately, seed ecology in such ecosystems has received little attention, especially regarding seed traits, germination responses to abiotic factors and the potential role of phylogenetic relatedness on such features Here, we provide the first quantitative and phylogenetically-informed synthesis of the seed functional ecology of Brazilian rock outcrop vegetation, with a particular focus on quartzitic and ironstone campo rupestre.
METHODS: Using a database of functional trait data, we calculated the phylogenetic signal of seven seed traits for 371 taxa and tested whether they varied among growth forms, geographic distribution, and microhabitats. We also conducted meta-analyses that included 4,252 germination records for 102 taxa to assess the effects of light, temperature, and fire-related cues on the germination of campo rupestre species and explored how the aforementioned ecological groups and seed traits modulate germination responses.
RESULTS: All traits and germination responses showed a moderate-to-strong phylogenetic signal. Campo rupestre species responded positively to light and had maximum germination between 20-25 ºC. The effect of temperatures beyond this range was moderated by growth form, species geographic distribution, and microhabitat. Seeds exposed to heat shocks above 80 °C lost viability, but smoke accelerated germination. We found a moderating effect of seed mass for in responses to light and heat shocks, with larger, dormant seeds tolerating heat better but less sensitive to light. Species from xeric habitats evolved phenological strategies to synchronise germination during periods of increased soil water availability.
CONCLUSIONS: Phylogenetic relatedness plays a major role in shaping seed ecology of Brazilian rock outcrop vegetation. Nevertheless, seed traits and germination responses varied significantly between growth forms, species geographic distribution and microhabitats, providing support to the regeneration niche hypothesis and the role of functional traits in shaping germination in these ecosystems.