On the accuracy of paleodiversity reconstructions: a case study in Antarctic Neogene radiolarians

Abstract

The deep-sea Cenozoic planktonic microfossil record has the unique characteristics of continuously well-preserved populations of most species, with virtually unlimited sample size, and therefore constitutes, in principle, a major resource for macroevolutionary research. Antarctic Neogene radiolarians in particular, are diverse, abundant and consistently well-preserved and evolved rapidly. This fauna is, in theory, a near-perfect testing ground for paleodiversity reconstructions. In this study we determined the diversity history of these faunas from a new quantitative, taxonomically complete data set from Neogene and Quaternary sections at several Antarctic sites. The pattern retrieved by our whole-fauna data set shows a significant, largely extinctionless ecological change in faunal composition and decrease in the evenness of species' abundances during the late Miocene, followed 3 Myr later, at around 5 Ma, by a significant drop in diversity. We tentatively associate this ecological event with a synchronous, regional change in the composition of the primary producers, but as yet cannot identify any environmental changes associated with the later extinction. Further, our whole-fauna diversity history was compared to diversity computed from much less complete, biostratigraphically oriented studies of species' occurrences, compiled in the Neptune database and reconstructed by using subsampling methodologies. Comparison of our whole-fauna and subsampling-reconstructed diversity patterns shows that the first-order trends are the same in both, suggesting that, to some degree, such literature compilations can be used to explore diversity history of plankton. However, our results also highlight substantial errors and distortions in the reconstructed diversity which make it poorly suited to more-detailed studies (e.g., for comparison of diversity history with paleoenvironmental history). We conclude that detailed studies of plankton diversity, and particularly those attempting to understand the relation between diversity and paleoceanographic change, should be based on taxonomically comprehensive, quantitative data.

Quantifying the Cenozoic marine diatom deposition history: links to the C and Si cycles

“…If a late Oligocene formation of the ACC is confirmed, then, considering the timing and the geographical extent of the late Oligocene diatom accumulation event, it is plausible that this new circulation pattern triggered increased opal deposition in the Southern Ocean. The increase in opal deposition seen in the Southern Ocean could also be relative and only reflect a decrease in carbonate deposition; however, carbonate microfossil deposition was still fairly abundant well into the Miocene (Lazarus and Caulet, 1993;Renaudie and Lazarus, 2013). The shift of the main diatom deposition locus starting at ca.…”

NSB (Neptune Sandbox Berlin): An expanded and improved database of marine planktonic microfossil data and deep-sea stratigraphy

“…No web interface was available, or possible with the limited funding provided, but basic data upload functionality was provided by an external python app. Only four papers were directly generated from this initial 'members only' offline implementation: Hannisdal et al (2012), Lazarus et al (2012), Renaudie and Lazarus (2013), and Lazarus et al (2014). While the other papers were studies of diversity dynamics, the Lazarus et al (2012) paper specifically addressed the main concern raised earlier by Spencer-Cervato (1999): that occurrence data in Neptune included a significant number of outliers, i.e., species occurrences at geologic ages that were not in accordance with the bulk of the occurrence data for that species.…”

Raritas and RaritasVox: Programs for counting high diversity categorical data with highly unequal abundances

“…species diversity at infinite sample size). From (Renaudie & Lazarus, 2013). Configuration file to populate interface with category names.…”