Data from: Holocene variability of an Amazonian hyperdominant

Little is known regarding the long-term stability or instability of Amazonian plant communities. We assessed whether the most abundant species, hyperdominants, may have risen to prominence at the Pleistocene–Holocene transition, following subsequent changes in moisture regimes, or as a result of human activity later in the Holocene. The fossil pollen history of the commonest western Amazonian tree, Iriartea deltoidea (hereafter Iriartea), is investigated using fossil pollen data from 13 lakes. Iriartea is a monospecific genus with diagnostic pollen. It is also considered a ‘useful’ plant, and its abundance could have been enriched by human action. Iriartea pollen was found to have increased in abundance in the last 3000 years, but did not show a consistent relationship with human activity. The suggestion that the hyperdominants in modern Amazonian forests are a legacy of pre-Columbian people is unsupported. The abundance of Iriartea pollen is related to increasing precipitation, not human activity over the last 3000 years. This member of the hyperdominant category of Amazonian trees has only recently acquired this status. Synthesis. Our findings are consistent with the observation that communities in complex systems are ephemeral. The populations of even the most abundant species can change over a few tens of generations. The relative abundance of tree species, even in relatively stable systems such as those of Amazonian floodplains, changes on ecological not evolutionary timescales.目前学界对亚马孙植物群落的长期稳定性与不稳定性尚知之甚少。本研究旨在探究亚马孙最丰富的物种——超优势植物（hyperdominants）——是否在更新世-全新世过渡期崛起，亦或是随后续水分状况的变化，或是全新世晚期人类活动的影响而成为优势类群。本研究利用13个湖泊的化石花粉数据，对亚马孙西部最常见的树种三角叶伊利亚特椰（Iriartea deltoidea，下文简称Iriartea）的化石花粉记录展开分析。该属为单型属，其花粉具有诊断性特征；同时该植物被视为"具有经济价值"的类群，其丰度可能因人类活动而提升。研究发现，过去3000年中Iriartea的花粉丰度有所上升，但并未与人类活动呈现出稳定的关联。此前提出的"现代亚马孙森林中的超优势植物是前哥伦布时期人类活动的遗留产物"这一假说，并无实证支撑。过去3000年中，Iriartea的花粉丰度变化与降水量增加相关，而非人类活动。作为亚马孙树木超优势类群的一员，该物种直至近期才获得这一生态地位。综合讨论：本研究结果与复杂系统中群落具有短暂性的观测结论一致。即使是最优势的物种，其种群数量也可在数十代的时间尺度内发生变化。即便在亚马孙泛滥平原这类相对稳定的生态系统中，树木物种的相对丰度变化也发生在生态时间尺度，而非进化时间尺度之上。