MICRO- AND MACROEVOLUTION OF THE CENOZOIC PLANKTONIC FORAMINIFERA

Planktonic foraminifera have one of the richest species-level fossil records of any group throughout the Cenozoic. Their distinctive morphologies and abundance in the fossil record allows for high-fidelity assessment of micro- and macroevolutionary processes and patterns over million-year timescales. Here we present an updated phylogeny of Cenozoic Globigerinoidea ("macroperforates") incorporating new taxonomic revisions and integrating morphospecies and lineages, and, for the first time, an integrated phylogeny of the remaining groups of Cenozoic planktonic foraminifera (including "microperforates"). The new phylogeny, in combination with the recently published Triton database (Fenton et al., 2021), has been employed to explore morphological variability across a number of speciation events throughout the Neogene (~23 Ma – Recent). Paired single-specimen stable isotope and morphological analysis of the macroperforate genera Globigerinella and Beella demonstrate that there is no correlation between depth habitat in the water column and extent of clavate chamber extension. An interesting observation, however, was that Globigerinella adamsi was seen to rise in the water column after speciation as temperatures increased. In contrast Globigerinella calida was seen to drop from a thermocline dweller to a sub thermocline dweller after speciation. A further high-resolution morphological analysis of the microperforate genera Candeina and Globigerinatella was used to explore morphological plasticity across speciation events, initial findings suggest considerable plasticity within 2 million years of speciation with the development of 17 distinct morphotypes prior to the establishment of more stable morphospecies concepts. This work highlights the utility of using the Triton database and the updated planktonic foraminifera phylogenies for detailed microevolutionary studies which shed light on morphological plasticity throughout speciation.