Data from: Ecological incumbency impedes stochastic community assembly in Holocene foraminifera from the Huon Peninsula, Papua New Guinea

Persistence in the structure of ecological communities can be predicted both by deterministic and by stochastic theory. Evaluating ecological patterns against the neutral theory of biodiversity provides an appropriate methodology for differentiating between these alternatives. We traced the history of benthic foraminiferal communities from the Huon Peninsula, Papua New Guinea. From the well-preserved uplifted reef terrace at Bonah River we reconstructed the benthic foraminiferal communities during a 2200-year period (9000–6800 yr B.P.) of reef building during the Holocene transgressive sea-level rise. We found that the similarity of foraminiferal communities was consistently above 60%, even when comparing communities on either side of a massive volcanic eruption that smothered the existing reef system with ash. Similarly, species diversity and rank dominance were unchanged through time. However, similarity dropped dramatically in the final stages of reef growth, when accommodation space was reduced as sea-level rise slowed. We compared the community inertia index (CII) computed from the observed species abundances with that predicted from neutral theory. Despite the differences in foraminiferal community composition in the younger part of the reef sequence, we found an overall greater degree of community inertia with less variance in observed communities than was predicted from neutral theory, regardless of foraminiferal community size or species migration rate. Thus, persistent species assemblages could not be ascribed to neutral predictions. Ecological incumbency of established foraminiferal species likely prevented stochastic increases in both migrant and rare taxa at the Bonah River site. Regardless of the structuring mechanisms, our reconstruction of Holocene foraminiferal assemblages provides historical context for the management and potential restoration of degraded species assemblages.

生态群落结构的持续性可通过确定性理论与随机性理论共同预测。针对生物多样性中性理论（neutral theory of biodiversity）验证生态学格局，是区分这两类理论的合适研究方法。我们对巴布亚新几内亚休恩半岛的底栖有孔虫群落（benthic foraminiferal communities）历史展开了追溯。在博纳河保存完好的抬升礁台处，我们重建了全新世海侵海平面上升期间，为期2200年（距今9000~6800年）的造礁过程中底栖有孔虫群落的演化序列。研究发现，即便对比大规模火山喷发（该喷发以火山灰覆盖了原有礁体系统）前后的群落，有孔虫群落的相似性始终高于60%。与之同步的是，物种多样性与等级优势度随时间并未发生显著改变。但在礁体发育的最终阶段，随着海平面上升放缓导致可容空间（accommodation space）缩减，群落相似性出现了急剧下降。我们将基于观测物种丰度计算得到的群落惯性指数（community inertia index, CII），与中性理论预测得到的指数进行了对比。尽管礁体序列中较年轻层位的有孔虫群落组成存在差异，但整体而言，观测群落的惯性程度更高，且方差小于中性理论的预测结果，这一结论不受有孔虫群落规模或物种迁移速率的影响。由此可见，持续性物种集合无法通过中性理论得到解释。博纳河点位上已建立的有孔虫物种所具备的生态在位性，大概率阻止了迁移类群与稀有类群的随机性增殖。无论调控群落结构的具体机制为何，我们对全新世有孔虫物种集合的重建工作，都为退化物种集合的管理与潜在修复提供了重要的历史参照依据。