Small seed selects for mast seeding in perennial plants

Aim: Reproduction in perennial plants varies from relatively constant among years to production of massive and synchronous seed crops at irregular intervals, a reproductive strategy called mast seeding. The sources of that interspecific differences in the extent of interannual variation in seed production are largely unknown. Location: Interannual variation in seed production of 340 plant species located world-wide. Methods: We conducted a global meta-analysis of 340 animal-dispersed species to quantify how the interannual variability of seed crops of plants can be explained by seed mass, dispersal mode, phylogeny and climate. Results: Phylogenetic analysis indicated that interannual variation in seed production and seed mass tend to be similar in related species owing to their shared evolutionary. Interannual variation in seed production was 1.22 times higher in synzoochorous compared to endozoochorous species. Moreover, production of small seeds was associated with higher interannual variation in seed production although synzoochorous species produce larger seeds than endozoochorous species. Precipitation rather than temperature showed significant positive effect on interannual variation in seed production. Seed mass and dispersal mode contribute more to interannual variation in seed production than phylogeny, climate and fruit type. Main conclusion: Our study lends support to a long-standing notion that interspecific variation in masting intensity is largely shaped by the interactions of plants with animals. Masting is avoided when interannual variation in seed production can harm mutualists and promoted when satiation can decrease predation and increase seed dispersal.研究目标：多年生植物的繁殖策略年际差异显著，既存在各年间结实量相对稳定的模式，也会不定期出现大量同步结种的情况，这种繁殖策略被称为丰年结实（mast seeding）。目前学界对造成不同物种间种子产量年际波动幅度差异的成因仍知之甚少。 研究覆盖范围：全球分布的340种植物的种子产量年际波动特征。 研究方法：本研究针对340种动物传播种子的植物开展全球元分析，旨在量化植物种子库的年际波动可通过种子质量、传播方式、系统发育关系以及气候因子得到何种程度的解释。 研究结果：系统发育分析结果显示，亲缘关系较近的物种间，种子产量年际波动与种子质量往往具有相似性，这源于它们共享的进化历史。体外动物传播（synzoochorous）物种的种子产量年际波动程度较体内动物传播（endozoochorous）物种高出1.22倍。此外，尽管体外动物传播物种的种子质量普遍高于体内动物传播物种，但小型种子的生产往往与更高的种子产量年际波动相关联。相较于气温，降水量对种子产量年际波动具有显著的正向影响。相较于系统发育关系、气候因子与果实类型，种子质量和传播方式对种子产量年际波动的解释度更高。 主要结论：本研究为一个长期存在的学术观点提供了支撑：不同物种间丰年结实强度的差异，主要由植物与动物的相互作用所塑造。当种子产量的年际波动会损害互利共生伙伴时，植物会规避丰年结实策略；而当通过同步结实可降低捕食压力、提升种子传播效率时，植物则会倾向于采用该策略。