Metacommunity analyses show an increase in ecological specialisation throughout the Ediacaran period

Abstract

The first animals appear during the late Ediacaran (572 to 541 Ma); an initial diversity increase was followed reduction in diversity, often interpreted as catastrophic mass extinction. We investigate Ediacaran ecosystem structure changes over this time period using the “Elements of Metacommunity Structure” framework to assess whether this diversity reduction in the Nama was likely caused by an external mass extinction, or internal metacommunity restructuring. The oldest metacommunity was characterised by taxa with wide environmental tolerances, and limited specialisation or intertaxa associations. Structuring increased in the second oldest metacommunity, with groups of taxa sharing synchronous responses to environmental gradients, aggregating into distinct communities. This pattern strengthened in the youngest metacommunity, with communities showing strong environmental segregation and depth structure. Thus, metacommunity structure increased in complexity, with increased specialisation and resulting in competitive exclusion, not a catastrophic environmental disaster, leading to diversity loss in the terminal Ediacaran. These results reveal that the complex eco-evolutionary dynamics associated with Cambrian diversification were established in the Ediacaran.

Increases in reef size, habitat and metacommunity complexity associated with Cambrian radiation oxygenation pulses

“…The 'Elements of Metacommunity Structure' framework used here is a hierarchical analysis that identifies properties in site-byspecies presence/absence matrices that are related to the underlying processes, such as species interactions, dispersal, and environmental filtering that shape species distributions 10 . Application to various marine and terrestrial palaeocommunities has demonstrated the robustness of these methods to fossil data and sample size variations 13,14 . There are fourteen different types of metacommunity structure which are determined by the calculation of three metacommunity metrics: Coherence, Turnover, and Boundary Clumping, which reveal different controlling processes of underlying metacommunity structure 10,[15][16][17][18] .…”

Addressing biodiversity loss by building a shared future

“…Considering that, even for some well-studied taxonomic groups, the current rates of extinction are unknown or seem to have been substantially underestimated [3,4], global biodiversity is in jeopardy.A cursory survey of biodiversity-related papers that have been published in the journal in the past year reveals several principal topics. In this issue alone, we feature work addressing the biodiversity of marine communities half a billion years apart [5,6] and the use of artificial intelligence to automate the surveillance of threatened species [3].Across the past year, one topic to emerge has been how biodiversity has changed in the past, with papers attempting to infer what forces, both biotic and abiotic, have driven these changes, often with the implicit or explicit expectation that we can learn lessons about future change. These papers include (in roughly temporal order) studies of ancient Ediacaran animal communities [5], end-Cretaceous sharks [7], Cenozoic snakes [8], and cold-water corals over the past 20,000 years [6] (Fig 1).…”

“…A cursory survey of biodiversity-related papers that have been published in the journal in the past year reveals several principal topics. In this issue alone, we feature work addressing the biodiversity of marine communities half a billion years apart [5,6] and the use of artificial intelligence to automate the surveillance of threatened species [3].…”

“…Another paper proposes the use of machine learning to avoid the time-consuming and potentially biased reliance on human experts for judging extinction risk [3]. A fourth study intriguingly reveals the Newfoundland, Canada, subjects of a metacommunity analysis of shifts in biodiversity more than 540 million years ago [5]. Top right: Late Cretaceous sharks' teeth from southern Sweden, which contributed to a new picture of how shark biodiversity was-and was not-impacted by the end-Cretaceous extinction event [7].…”

“…More than half a billion years of biodiversity. Top left: Fossils of Ediacaran creatures Fractofusus and Plumeropriscum fromNewfoundland, Canada, subjects of a metacommunity analysis of shifts in biodiversity more than 540 million years ago[5]. Top right: Late Cretaceous sharks' teeth from southern Sweden, which contributed to a new picture of how shark biodiversity was-and was not-impacted by the end-Cretaceous extinction event[7].…”