Data from: On the benefits of being redundant: low compositional fidelity of diatom death assemblages does not hamper the preservation of environmental gradients in shallow lakes

Comparisons between death assemblages and their source living communities are among the most common actualistic methods of evaluating the preservation of compositional and environmental information in fossil assemblages. Although live-dead studies have commonly focused on marine mollusks, the potential of diatoms to preserve ecological information in continental settings has been overlooked. Thus, little is known about the nature and magnitude of the taphonomic biases affecting live-dead agreement of diatom assemblages, despite their extensive application as modern and fossil bioindicators in paleoecological and paleoenvironmental reconstructions. In this study, I analyzed three live-dead data sets in order to evaluate the compositional and environmental fidelity exhibited by diatom death assemblages in shallow lakes. I find that diatom death assemblages (DAs) do differ significantly in their taxonomic composition from living assemblages (LAs), mainly as a consequence of (1) differences in the temporal resolution between time-averaged DAs and non-averaged LAs, and (2) differential preservation of diatom taxa related to the intrinsic properties of their valves. Despite compositional dissimilarities, DAs were able to capture the same environmental gradients as LAs, with high significance. This decoupling between live-dead agreement in community composition and community response to gradients can be related to the existence of at least two mutually exclusive subsets of species that significantly captured compositional dissimilarities based on the full set of the species in the three lakes. This functional redundancy implies that the between-sample relationships of living assemblages can be significantly preserved by DAs even if some taxa are removed by taphonomic processes. The preservation of environmental gradients thus does not require good preservation of all living taxa. Structural redundancy compensates for the loss of compositional fidelity caused by postmortem processes in the diatom data set.

死亡集合体（death assemblages）与其对应的现生群落的对比，是评估化石组合（fossil assemblage）中分类学组成与环境信息保存情况的最常用现实论方法之一。
尽管现生-死亡对比研究（live-dead study）通常以海洋软体动物为研究对象，但硅藻（diatoms）在陆相环境中保存生态信息的潜力却长期被忽视。
因此，尽管硅藻作为现代与化石生物指示物（bioindicator）被广泛应用于古生态与古环境重建，但学界对影响硅藻组合现生-死亡匹配度的埋藏学偏差（taphonomic bias）的本质与强度仍知之甚少。
本研究针对三个现生-死亡对比数据集（dataset）展开分析，旨在评估浅水湖泊中硅藻死亡集合体（DAs）所展现出的组成与环境保真度（fidelity）。
研究发现，硅藻死亡集合体（DAs）的分类学组成与现生集合体（LAs）存在显著差异，其主要成因包括两点：一是经时间平均作用的DAs与非时间平均的LAs之间存在时间分辨率差异；二是硅藻类群的差异保存与其壳瓣（valve）的固有属性相关。
尽管二者分类学组成存在差异，但DAs仍能高度显著地重现与LAs一致的环境梯度（environmental gradient）。
群落组成层面的现生-死亡匹配度与群落对环境梯度的响应之间存在这种解耦（decoupling）现象，这可能与三个湖泊的全部物种种群中存在至少两类互斥的物种类群子集有关——这类子集能够显著区分群落组成差异。
这种功能冗余（functional redundancy）意味着，即便部分类群因埋藏过程遭到移除，DAs仍能显著保留现生集合体的样本间群落关联特征。
因此，环境梯度的保存并不要求所有现生类群都得到完好保存。结构冗余（structural redundancy）可弥补硅藻数据集中因死后过程导致的组成保真度损失。