Data from: Recolonisation strategies of early animals in the Avalon (Ediacaran 574 – 560 Ma)

The first geographically widespread metazoans are found in the Avalon
assemblage (Ediacaran; 574 – 560 Ma). These early animals were regularly
disturbed by sedimentation events such as ash flows and turbidites,
leading to an apparent “resetting” of communities. However, it is not
clear how biological legacies – remains or survivors of disturbance events
– influenced community ecology in the Avalon. Here, we use spatial point
process analysis on 19 Avalon palaeocommunities to test whether two forms
of biological legacy (fragmentary remains of Fractofusus and surviving
frondomorphs) impacted the recolonisation dynamics of Avalon
palaeocommunities. We found that densities of Fractofusus were increased
around the Fractofusus fragments, suggesting that they helped to
recolonise the post-disturbance substrate, potentially contributing to the
Fractofusus dominance found in 8 of the 19 palaeocommunities. However, we
found no such effects for survivor fronds. Our results suggest that the
evolution of height was for long-distance dispersal rather than local
recolonisation. In modern deep-sea environments, there is a trade-off
between local and long-distance dispersal, and our work demonstrates that
this differentiation of reproductive strategies had already developed in
the early animals of the Avalon.

地理分布最为广泛的后生动物（metazoans）发现于阿瓦隆组合（Avalon Assemblage，埃迪卡拉纪（Ediacaran）；574~560 Ma）。这类早期后生动物频繁受到火山灰流、浊流等沉积事件的干扰，致使群落出现显著的“重置”现象。然而目前尚不清楚生物遗留物（biological legacies）——即扰动事件留下的残骸或幸存个体——如何影响阿瓦隆群落的生态动态。本研究对19个阿瓦隆古群落（palaeocommunities）开展空间点过程分析（spatial point process analysis），以检验两类生物遗留物——分形虫（Fractofusus）的破碎残骸与幸存的叶状形态类生物（frondomorphs）——是否对阿瓦隆古群落的再定植动态（recolonisation dynamics）产生影响。研究发现，分形虫的个体丰度在其破碎残骸周围显著升高，表明这类残骸可助力扰动后基底的再定植，这或许促成了19个古群落中8个群落内分形虫的优势地位。但未观察到幸存叶状个体存在此类效应。本研究结果表明，体型高度的演化是为了实现长距离扩散，而非局域再定植。在现代深海环境中，局域扩散与长距离扩散之间存在权衡取舍，本研究证实，这种繁殖策略的分化早在阿瓦隆的早期后生动物类群中就已出现。