Into the deep. Do changes in ecology lead changes in morphology in Neogene clavate planktonic foraminifera?

Iterative evolution is the repeated evolution of similar or parallel traits in the development of the same evolutionary line or clade. Iterative morphological evolution in planktonic foraminifera has long been demonstrated throughout the history of the group (e.g. Hart 1980). Furthermore, the iterative acquisition of certain characters have been linked to repeated invasion of specific ecological niche habitats through time; e.g. chamber elongation (clavate chambers) in lineages which show migration to deeper water environments (Coxall et al. 2007). Although this relationship is well documented, sampling at a resolution that would permit the distinction between whether changes in ecology drove morphological variation, or changes in morphology permitted invasion of new environmental niches has yet to be conducted. An important strength of PF as a model system is the ability to sample their fossil record at will and, in certain, locations at very high resolution. This will allow us to identify the explanatory and response variables driving ecological and morphological evolution.
The selected species will be directly sampled from the fossil record using deep-sea core material that has robust chronologies in order to pinpoint the temporal aspects of any changes. We will target core material that has the best-defined geomagnetic and astrochronologies, and local dates at focal sites will be fine-tuned in collaboration with work undertaken as part of the associate NERC large grant “Does developmental plasticity influence speciation” (NE/P019269/1).

The project will focus upon the Globigerinella, Beella and Protentella lineages of the Neogene macroperforate planktonic foraminifera; all of which have evolved at least one morphospecies that exhibits chamber elongation. The project will be grounded upon revision of the alpha taxonomy and will be broken into the following components:

1. Produce the first statistical data into the morphological evolution and speciation in the Globigerinella, Beella and Protentella lineages (a total of 10 morphospecies), testing without use of a priori hypotheses where the boundaries between species lie. Forty uniformly distributed samples of 100 individuals along length of the lineages will be imaged and measured using Image Pro Premier software, these will then be analyzed following the approach successfully employed by (Pearson & Ezard 2014).
2. Geochemical analysis of foraminiferal calcite will provide information about changes in ecology. The carbon and oxygen isotopic signatures of foraminiferal shells partly reflect equilibrium with the ambient water chemistry at the time of calcification and also biotic and kinetic fractionations of dissolved inorganic carbon from which the foraminifera construct their shells. Identifying shifts in geochemical signatures of successive populations prior to and after perceived changes in morphology will demonstrate whether changes in ecology and environment lead changes in morphology or visa versa.
3. The approach will be extended by studying multiple sites to determine and match morphological and isotopic trends to assess the weight of evidence for alternative modes of speciation and potential diachroneity of morphological and ecological change.
The work is easily divisible into publications that will form consecutive chapters of the PhD thesis/publications. The first will address: Revision of the alpha taxonomy. The second: disentangling whether changes in ecology drive morphological variation, or changes in morphology permitted invasion of new environmental niches. The third: the effects of geographic range and provinciality on speciation mode and diachroneity of morphological and ecological change. This interdisciplinary project will provide the successful PhD candidate with highly valued and sought-after tools for investigating past climates and species interactions, such as geochemistry, morphometrics, taxonomy and phylogenetic and statistical modelling. This will equip the student with the necessary expertise to become the next generation of palaeontological and climate scientist, ready to carry out their own programme of innovative scientific research.