Cenozoic ostracode biodiversity in the Indo-Pacific

Abstract

Biodiversity is dynamic with time, and can be highly variable. Peak shallow marine diversity currently centers in southeastern Asia in the Indo-west Pacific (IWP) or Indo-Australian Archipelago hotspot, but its presence has only been apparent since the middle Cenozoic and it is still unclear how diversity has developed to form this locus. Fossil diversity during the Miocene, Pliocene, and Pleistocene was investigated for a diverse, widespread and abundant microfossil class (Crustacea: Ostracoda) from Java island (Indonesia) and the Philippines. An unprecedented number of taxa from this collection, half of which may be new, were discovered. From low species, generic and familial diversity in the Miocene, there was an increase in the Pliocene, the period where diversity was also most variable. Diversity subsequently declined from the Pleistocene onwards. Though approximate trends are similar among taxonomic levels, family diversity was significantly different to species and genera. These epochal diversities were not statistically significant, but sample clustering by time and location can be observed. Although the majority of ostracodes were common to multiple time intervals, taxa that contributed the most to similarities within temporal and locality groupings were almost identical to those responsible for dissimilarities between paired time and location comparisons. Fluctuating diversity with time and the occurrences of cosmopolitan fauna antecedent to the IWP suggest the effect of Pliocene and Pleistocene eustatic changes, and Cenozoic tectonic events. A tropical ostracode hotspot may have occurred before the present, or lie outside of the studied time and region.