Biology subjects

Close, R. A.

Publications and source records attributed to Close, R. A..

3 recordsLinked to original sources

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

Tetrapod species-area relationships across the Cretaceous-Paleogene mass extinction

Mass extinctions are rare but catastrophic events that profoundly disrupt biodiversity. Widelyaccepted consequences of mass extinctions, such as biodiversity loss and the appearance of temporary disaster taxa, imply that nested species-area relationships (SARs, or how biodiversity scales with area) should change dramatically across these events: specifically, both the slope (reflecting the rate of accumulation of new species with increasing area) and intercept (reflecting the density of species at local scales) of the power-law relationship should decrease. However, these hypotheses have not been tested, and the contribution of variation in the SAR to diversity dynamics in deep time has been neglected. We use fossil data to quantify nested SARs in North American terrestrial tetrapods through the Cretaceous-Paleogene (K/Pg) mass extinction (Campanian-Ypresian). SARs vary substantially through time and among groups. In the pre-extinction interval (Maastrichtian), unusually shallow SAR slopes (indicating low beta diversity or provinciality) drive low total regional diversity in dinosaurs, mammals and other tetrapods. In the immediate post-extinction interval (Danian), the explosive diversification of mammals drove high regional diversity via a large increase in SAR slope (indicating higher beta diversity or provinciality), and only a limited increase in SAR intercept (suggesting limited diversity change at small scales). This contradicts the expectation that post-extinction biotas should be regionally homogenized by the spread of disaster taxa and impoverished by diversity loss. This early post-extinction increase in SAR slope was followed in the Thanetian-Selandian ([~]4.4. myr later) by increases in the intercept, indicating that diversity dynamics at local and regional scales did not change in synchrony. These results demonstrate the importance of SARs for understanding deep-time diversity dynamics, particularly the spatial dynamics of recovery from mass extinctions.

paleontology↗

bioRxiv2024

Apparent timescaling of fossil diversification rates is caused by sampling bias

Negative scaling relationships between both speciation and extinction rates on the one hand, and the age or duration of organismal groups on the other, are pervasive, and recovered in both molecular phylogenetic and fossil time series. The agreement between molecular and fossil data hints at a universal cause, and potentially to incongruence between micro- and macroevolution. However, the existence of negative rate scaling in fossil time series has not undergone the same level of scrutiny as in molecular data. Here, we analyse the marine fossil record across the last ~538.8 Ma of the Phanerozoic to investigate the presence and strength of negative rate scaling. We find that negative rate scaling arises under commonly applied age range-based per-capita rates, which do not control for sampling bias, but are severely reduced or absent when metrics are used that do correct for sampling. We further show by simulation that even moderately-incomplete sampling of species occurrences through time may induce rate scaling. We thus conclude that there are no significant scaling relationships present in these fossil clades, and that any apparent trend is caused by sampling artefacts and taxonomic practices. If rate scaling in molecular phylogenies is genuine, the absence of such a relationship in the fossil record will provide a valuable benchmark and constraint on what processes can cause it. HighlightsO_LIStudies have found that fossil and molecular diversification rates scale with time C_LIO_LISuch rate scaling hints at a disconnect between micro- and macroevolution C_LIO_LIThese trends are absent from the fossil record when controlling for sampling biases C_LIO_LIRate scaling in general may be artefactual, or fossils could show distinct patterns C_LI

evolutionary biology↗