Persistent ecological shifts in marine molluscan assemblages across the end-Cretaceous mass extinction

Abstract

Contemporary biodiversity loss and population declines threaten to push the biosphere toward a tipping point with irreversible effects on ecosystem composition and function. As a potential example of a global-scale regime shift in the geological past, we assessed ecological changes across the end-Cretaceous mass extinction based on molluscan assemblages at four well-studied sites. By contrasting preextinction and postextinction rank abundance and numerical abundance in 19 molluscan modes of lifeeach defined as a unique combination of mobility level, feeding mode, and position relative to the substrate-we find distinct shifts in ecospace utilization, which significantly exceed predictions from null models. The magnitude of change in functional traits relative to normal temporal fluctuations at far-flung sites indicates that molluscan assemblages shifted to differently structured systems and faunal response was global. The strengths of temporal ecological shifts, however, are mostly within the range of preextinction site-to-site variability, demonstrating that local ecological turnover was similar to geographic variation over a broad latitudinal range. In conjunction with varied site-specific temporal patterns of individual modes of life, these spatial and temporal heterogeneities argue against a concerted phase shift of molluscan assemblages from one well-defined regime to another. At a broader ecological level, by contrast, congruent tendencies emerge and suggest deterministic processes. These patterns comprise the well-known increase of deposit-feeding mollusks in postextinction assemblages and increases in predators and predator-resistant modes of life, i.e., those characterized by elevated mobility and infaunal life habits.end-Cretaceous mass extinction | regime shift | functional groups | mollusks | ecospace

Impact of the Late Triassic mass extinction on functional diversity and composition of marine ecosystems

“…Global functional stability appears to be a common factor among mass extinction events, having been previously recorded for the Late Triassic (Kiessling et al . ), late Permian (Foster & Twitchett ) and the end‐Cretaceous (Aberhan & Kiessling ). The LTE fits the ‘skeleton crew hypothesis’ of Foster & Twitchett (), in which each ecological guild survives, but is ‘manned’ by only a few individual taxa during the recovery period.…”

“…a regime shift) is key to understanding mass extinction events (Barnosky et al . ; Aberhan & Kiessling ). The LTE has been understudied in comparison with other major Phanerozoic biotic crises (Twitchett ) and, despite the importance of functional diversity changes or ecological regime shifts on ecosystem function, a palaeoecological perspective on long‐term trends through deep‐time, including the effects of mass extinctions, is still lacking (Villéger et al .…”

“…) and studies of both the late Permian (Dineen et al . ; Foster & Twitchett ) and end‐Cretaceous (Aberhan & Kiessling ) mass extinction events. The following individual hypotheses were tested: (1) in common with the Late Permian extinction (Foster & Twitchett ), despite significant taxonomic losses, the LTE did not result in a reduction in global functional diversity; (2) sessile suspension feeders were selected against, compared to other modes of life across the LTE; (3) heavily calcified organisms were selected against and suffered higher extinction rates than lightly calcified taxa; and (4) taxonomic and functional diversity loss was greater in the tropics than at higher latitudes.…”

Life in the Aftermath of Mass Extinctions

“…At the same time, the composition and geochemistry of the rocks being formed often indicate a prolonged interval of earth system change [16,18]. On the re-establishment of pre-extinction-like complexity in ecosystems, the fundamental organization (structure) and function of ecosystems is often permanently changed ( Figure 2B) [13,[39][40][41]. How do we know that ecosystems changed, and what does it mean for understanding the evolution of life in the aftermath?…”

Biological Correlates of Extinction: What Does Differentiate Survivors From Victims?

“…Mass extinctions are also thought to promote ecological restructurings of the biota (DINEEN et al, 2014;ABERHAN ;KIESSLING, 2015). Extinctions in these periods would open up vacant niches (LEKEVICIUS, 2009), or ecospace (BENTON, 1995;LOCKWOOD, 2008), allowing dominant species to be replaced by others, and also allowing the diversification of marginal taxa (JABLONSKI, 2005).…”