Saupe, E. E. | bioRxiv Science

bioRxiv2025

Reefal regions were biodiversity hotspots throughout the Phanerozoic

Reefs are important hotspots of marine biodiversity today, and acted as cradles of diversification in the geological past. However, we know little about how the diversity of reef-supporting regions varied through deep time, and how this differed from other regions. We quantified regional diversity patterns in reef-supporting and non-reef-supporting regions in the fossil record of Phanerozoic marine invertebrates. Diversity in reef-supporting regions is on average two- to three-fold higher than in non-reef-supporting regions, and has been remarkably stable over timescales of tens to hundreds of millions of years. This signal is present in both reefal and non-reefal facies within reef-supporting regions, suggesting that reefs enriched diversity in surrounding environments. Sepkoskis Modern Fauna, an assemblage of higher taxa that includes gastropods, bivalves and echinoids, has been a key component of reef-supporting regions since the Paleozoic, contrasting with its later rise to dominance in non-reef-supporting regions during the later Mesozoic-Cenozoic. One-Sentence SummaryRegions of the globe that supported reefal environments have been key hotspots of marine animal diversity for over 400 million years.

paleontology↗

bioRxiv2024

Spatially heterogeneous responses of planktonic foraminifera assemblages over 700,000 years of climate change

AimTo determine the degree to which assemblages of planktonic foraminifera track thermal conditions. LocationThe worlds oceans. Time periodThe last 700,000 years of glacial-interglacial cycles. Major taxa studiedPlanktonic foraminifera. MethodsWe investigate assemblage dynamics in planktonic foraminifera in response to temperature changes using a global dataset of Quaternary planktonic foraminifera, together with a coupled Atmosphere-Ocean General Circulation Model (AOGCM) at 8,000-year resolution. We use thermal deviance to assess assemblage responses to climate change, defined as the difference between the temperature at a given location and the bio-indicated temperature (i.e., the abundance-weighted average of estimated temperature optima for the species present). ResultsAssemblages generally tracked annual mean temperature changes through compositional turnover, but large thermal deviances are evident under certain conditions. The coldest-adapted species persisted in polar regions during warming but were not joined by additional immigrants, resulting in decreased assemblage turnover with warming. The warmest-adapted species persisted in equatorial regions during cooling. Assemblages at mid latitudes closely tracked temperature cooling and showed a modest increase in thermal deviance with warming. Main conclusionsPlanktonic foraminiferal assemblages were generally able to track or endure temperature changes: as climate warmed or cooled, bio-indicated temperature also became warmer or cooler, although to a variable degree. At polar sites under warming and at equatorial sites under cooling, the change in temperature predicted from assemblage composition was less than, or even opposite to, expectations based on estimated environmental change. Nevertheless, all species survived the accumulation of thermal deviance--a result that highlights the resilience and inertia of planktonic foraminifera on an assemblage level to the last 700,000 years of climate change, which might be facilitated by broad thermal tolerances or depth shifts.

paleontology↗