The importance of neutral over niche processes in structuring Ediacaran early animal communities

Abstract

The relative influence of niche vs. neutral processes in ecosystem dynamics is an on‐going debate, but the extent to which they structured the earliest animal communities is unknown. Some of the oldest known metazoan‐dominated paleocommunities occur in Ediacaran age (~ 565 million years old) strata in Newfoundland, Canada and Charnwood Forest, UK. These comprise large and diverse populations of sessile organisms that are amenable to spatial point process analyses, enabling inference of the most likely underlying niche or neutral processes governing community structure. We mapped seven Ediacaran paleocommunities using LiDAR, photogrammetry and a laser line probe. We found that neutral processes dominate these paleocommunities, with niche processes exerting limited influence, in contrast with the niche‐dominated dynamics of modern marine ecosystems. The dominance of neutral processes suggests that early metazoan diversification may not have been driven by systematic adaptations to the local environment, but instead may have resulted from stochastic demographic differences.

Deciphering trophic interactions in a mid-Cambrian assemblage

“…al., 2019), and we found this to be true for our ABM simulations ( Figure S4). This result supports the premise that fossil abundance correlations might correspond to potential species interactions, where the degree of preservation bias is low, such as in extremely well-preserved assemblages like the Burgess shale (Saleh et al, 2020), and census-like preservation of Ediacaran communities (Mitchell et al, 2019). Furthermore, the distribution of abundance correlations should characterize system-level interactions.…”

Spatial point pattern analysis of traces (SPPAT): An approach for visualizing and quantifying site-selectivity patterns of drilling predators

“…The recognition that predation traces on prey skeletons are spatially explicit and can be mapped enables the development of a proxy for site selectivity in drilling predation based on spatial point process modeling (Baddeley et al 2016). Here, we introduce the spatial point pattern analysis of traces (SPPAT), an approach for visualizing and quantifying the distribution of predation traces on shelled invertebrate prey, which includes improved collection of spatial information inherent to drillhole location, improved visualization of spatial trends, and distance-based statistics for hypothesis testing (see also Clapham et al [2003], Mitchell and Butterfield [2018], and Mitchell et al [2019] for examples that use a similar spatially explicit approach to describe the distribution of well-preserved Ediacaran fossils). We illustrate the SPPAT approach through case studies on museum samples of the Plio-Pleistocene venerid bivalve Lirophora latilirata (Conrad, 1841) from the Atlantic coastal plain of the United States, which has been previously used in studies on drilling predation (Hattori et al 2014; Klompmaker and Kelley 2015); drilling data from laboratory-based feeding trials of the tropical eastern Pacific naticid Notocochlis unifasciata (Lamarck, 1822) preying upon the venerid bivalve Iliochione subrugosa (W. Wood, 1828); and modern beach-collected samples of I. subrugosa from Central America.…”

Facilitating corals in an early Silurian deep‐water assemblage

“…2015), competitive interactions (Mitchell & Kenchington 2018) and interactions with different environmental settings (Mitchell et al . 2019, 2020). Recently, SPPA has also been applied to investigate drilling predation distribution in bivalves (Rojas et al .…”