Disentangling ecological and taphonomic signals in ancient food webs

Analyses of ancient food webs reveal important paleoecological processes
and responses to a range of perturbations throughout Earth’s history, such
as climate change. These responses can inform our forecasts of future
biotic responses to similar perturbations. However, previous analyses of
ancient food webs rarely accounted for key differences between modern and
ancient community data, particularly selective loss of soft-bodied taxa
during fossilization. To consider how fossilization impacts inferences of
ancient community structure we (1) analyzed node-level attributes to
identify correlations between ecological roles and fossilization potential
and (2) applied selective information loss procedures to food web data for
extant systems. We found that selective loss of soft-bodied organisms has
predictable effects on the trophic structure of “artificially fossilized”
food webs, because these organisms occupy unique, consistent food web
positions. Fossilized food webs misleadingly appear less stable (i.e.,
more prone to trophic cascades), with less predation and an
overrepresentation of generalist consumers. We also found that ecological
differences between soft- and hard-bodied taxa—indicated by distinct
positions in modern food webs—are recorded in an Early Eocene web, but not
in Cambrian webs. This suggests that ecological differences between the
groups have existed for ≥ 48 million years. Our results indicate that
accounting for soft-bodied taxa is vital for accurate depictions of
ancient food webs. However, the consistency of information loss trends
across the analyzed food webs means it is possible to predict how the
selective loss of soft-bodied taxa affects food web metrics, which can
permit better modeling of ancient communities.