Complex ecosystems predate the Cambrian explosion

(ORDO NEWS) — A study of the animal communities of the Ediacaran period (541-635 million years ago) showed that the Cambrian explosion – a sharp increase in biodiversity that occurred 540 million years ago – was not preceded by a mass extinction.

This event was the result of a natural change in complex ecological communities that appeared in the Late Ediacaran.

Some of the first multicellular organisms appeared in the Ediacaran period (541-635 million years ago) – the last geological period of the Neoproterozoic, followed by the Cambrian.

The beginning of the Ediacaran occurred at the end of the global glaciation, and the end coincided with the Cambrian explosion – a sharp increase in biodiversity. The fossil record showed that in the 40 million years before this event, the number of species declined sharply.

Scientists believed that this was due to some kind of environmental disaster. However, previous work has not explored the structure of ancient ecological communities.

To find evidence for an Ediacaran mass extinction, researchers from the University of Cambridge (UK) analyzed the metacommunity structure of three fossil complexes spanning the last 32 million years of the Ediacaran. The scientists also used data on ocean depth and rock characteristics.

The results of a study published in the journal PLOS Biology showed that the decline in biodiversity was not due to external factors, but to the internal restructuring of communities.

The oldest of the studied metacommunities was represented by species with wide ecological tolerance and limited specialization. Over time, the structuring and complexity of ecosystems has increased. Groups of organisms began to respond jointly to changes in the environment, which indicated their unification into communities.

At the end of the Ediacaran, species became highly specialized to their ecological niches and complex interactions between taxa emerged.

It is this structure that caused many species to disappear as a result of competition for ecological niches to which they were well adapted. This trend is observed during succession – a consistent and regular change of one biological community by another.

In addition, the study showed that the ecological traits and evolutionary dynamics commonly associated with the Cambrian explosion, such as animal adaptations to certain habitats, appeared in ecological communities as early as the late Ediacaran period, and not in the Cambrian, as previously thought.

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