Abundance does not predict extinction risk in the fossil record of marine plankton.

A major premise of ecological neutral theory is that population size is inversely related to extinction risk. This idea is central to modern biodiversity conservation efforts, which often rely on abundance metrics to partially determine species extinction risk. However, limited empirical studies have tested whether extinction is indeed more probable for species with low abundances. Here we use the fossil record of Neogene radiolaria to test the relationship between relative abundance and longevity (time from first to last occurrence). Our dataset includes abundance histories for 189 polycystine radiolarian species from the Southern Ocean, and 101 species from the tropical Pacific. Using linear regression analyses, we show that neither maximum nor average relative abundance are significant predictors of longevity in either oceanographic region. This suggests that neutral theory fails to explain the plankton ecological-evolutionary dynamics we observe. Extrinsic factors are likely more important than neutral dynamics in controlling radiolarian extinction.

Late Neogene Lophophaenidae (Nassellaria, Radiolaria) from the eastern equatorial Pacific.

Lophophaenidae is a clade of polycystine radiolarians that was highly abundant and diverse in the Late NeogeneRecent eastern equatorial Pacific (EEP). Despite their importance in fossil plankton assemblages, lophophaenids have been neglected because of their generally small size, complex morphology, and weak taxonomic framework. These challenges have left many lophophaenid concepts poorly defined or lacking formal description. Here we address this with a review of 101 lophophaenid taxa observed in EEP Middle MioceneRecent marine sediments. We discuss existing lophophaenid genera Amphiplecta Haeckel 1881, Arachnocorallium Haeckel 1887, Arachnocorys Haeckel 1860, Botryopera Haeckel 1887, Ceratocyrtis Btschli 1882, Lithomelissa Ehrenberg 1847, Lophophaena Ehrenberg 1847, and Peromelissa Haeckel 1881, including full species lists. We describe Pelagomanes n. gen., 23 new species: Amphiplecta kikimorae n. sp., Arachnocorys jorogumoae n. sp., Botryopera amabie n. sp., Botryopera babayagae n. sp., Botryopera bolotniki n. sp., Ceratocyrtis? chimii n. sp., Ceratocyrtis vila n. sp., Lithomelissa alkonost n. sp., Lithomelissa babai n. sp., Lithomelissa dybbuki n. sp., Lithomelissa sirin n. sp., Lophophaena arie n. sp., Lophophaena casperi n. sp., Lophophaena domovoi n. sp., Lophophaena gozui n. sp., Lophophaena ikiryo n. sp., Lophophaena ikota n. sp., Lophophaena kaonashii n. sp., Lophophaena leshii n. sp., Lophophaena rusalkae n. sp., Lophophaena shishigae n. sp., Lophophaena ushionii n. sp., and Pelagomanes ibburi n. sp., and one new subspecies, Arachnocorys pentacantha wanii n. subsp. In addition, we document 35 taxa in open nomenclature, and revise generic assignments of 10 species. The names of 32 previously-described species are upheld, but with clarified synonymies, discussion, and illustrations. This work contributes a practical framework for identifying tropical Late NeogeneRecent lophophaenid taxa, and demonstrates their rich morphological diversity.

Triton, a new species-level database of Cenozoic planktonic foraminiferal occurrences.

Planktonic foraminifera are a major constituent of ocean floor sediments, and thus have one of the most complete fossil records of any organism. Expeditions to sample these sediments have produced large amounts of spatiotemporal occurrence records throughout the Cenozoic, but no single source exists to house these data. We have therefore created a comprehensive dataset that integrates numerous sources for spatiotemporal records of planktonic foraminifera. This new dataset, Triton, contains >500,000 records and is four times larger than the previous largest database, Neptune. To ensure comparability among data sources, we have cleaned all records using a unified set of taxonomic concepts and have converted age data to the GTS 2020 timescale. Where ages were not absolute (e.g. based on biostratigraphic or magnetostratigraphic zones), we have used generalised additive models to produce continuous estimates. This dataset is an excellent resource for macroecological and macroevolutionary studies, particularly for investigating how species responded to past climatic changes.

Marine plankton show threshold extinction response to Neogene climate change.

Ongoing climate change is predicted to trigger major shifts in the geographic distribution of marine plankton species. However, it remains unclear whether species will successfully track optimal habitats to new regions, or face extinction. Here we show that one significant zooplankton group, the radiolaria, underwent a severe decline in high latitude species richness presaged by ecologic reorganization during the late Neogene, a time of amplified polar cooling. We find that the majority (71%) of affected species did not relocate to the warmer low latitudes, but went extinct. This indicates that some plankton species cannot track optimal temperatures on a global scale as assumed by ecologic models; instead, assemblages undergo restructuring and extinction once local environmental thresholds are exceeded. This pattern forewarns profound diversity loss of high latitude radiolaria in the near future, which may have cascading effects on the ocean food web and carbon cycle.

Raritas: a program for counting high diversity categorical data with highly unequal abundances.

Acquiring data on the occurrences of many types of difficult to identify objects are often still made by human observation, for example, in biodiversity and paleontologic research. Existing computer counting programs used to record such data have various limitations, including inflexibility and cost. We describe a new open-source program for this purpose-Raritas. Raritas is written in Python and can be run as a standalone app for recent versions of either MacOS or Windows, or from the command line as easily customized source code. The program explicitly supports a rare category count mode which makes it easier to collect quantitative data on rare categories, for example, rare species which are important in biodiversity surveys. Lastly, we describe the file format used by Raritas and propose it as a standard for storing geologic biodiversity data. 'Stratigraphic occurrence data' file format combines extensive sample metadata and a flexible structure for recording occurrence data of species or other categories in a series of samples.

Cenozoic planktonic marine diatom diversity and correlation to climate change.

Marine planktonic diatoms export carbon to the deep ocean, playing a key role in the global carbon cycle. Although commonly thought to have diversified over the Cenozoic as global oceans cooled, only two conflicting quantitative reconstructions exist, both from the Neptune deep-sea microfossil occurrences database. Total diversity shows Cenozoic increase but is sample size biased; conventional subsampling shows little net change. We calculate diversity from a separately compiled new diatom species range catalog, and recalculate Neptune subsampled-in-bin diversity using new methods to correct for increasing Cenozoic geographic endemism and decreasing Cenozoic evenness. We find coherent, substantial Cenozoic diversification in both datasets. Many living cold water species, including species important for export productivity, originate only in the latest Miocene or younger. We make a first quantitative comparison of diatom diversity to the global Cenozoic benthic ∂(18)O (climate) and carbon cycle records (∂(13)C, and 20-0 Ma pCO2). Warmer climates are strongly correlated with lower diatom diversity (raw: rho = .92, p<.001; detrended, r = .6, p = .01). Diatoms were 20% less diverse in the early late Miocene, when temperatures and pCO2 were only moderately higher than today. Diversity is strongly correlated to both ∂(13)C and pCO2 over the last 15 my (for both: r>.9, detrended r>.6, all p<.001), but only weakly over the earlier Cenozoic, suggesting increasingly strong linkage of diatom and climate evolution in the Neogene. Our results suggest that many living marine planktonic diatom species may be at risk of extinction in future warm oceans, with an unknown but potentially substantial negative impact on the ocean biologic pump and oceanic carbon sequestration. We cannot however extrapolate our my-scale correlations with generic climate proxies to anthropogenic time-scales of warming without additional species-specific information on proximate ecologic controls.