Research projects

Prof. Dr. Christian Klug

Branching spirals in deep time: Ammonoid phylogeny and macroecology

Leadership/contacts

Duration

October 2026 to September 2031

Funding sources

SNF, Personen- und Projektförderung

Collaborations

Summary

With over 11000 species and a fossil record spanning 320 million years, ammonoids belong to the most important group of macrofossils to study macroevolutionary and biodiversity patterns because of their abundance, species richness as well as their usefulness in biostratigraphy. In recent years, they have been increasingly included in palaeoenvironmental studies, and their palaeoecology is better understood through modelling and other analyses. Their phylogeny was rarely studied in the past 60 years, except for research focusing on subclades. This causes a massive discrepancy in knowledge compared to many other metazoan clades. The absence of a deep understanding of ammonoid phylogeny prevents quantitative studies of evolutionary processes and effects of macroecological changes. Without a phylogeny, it is difficult to understand how extinctions and recoveries were impacted by their life history strategies.
The scarcity of studies is often attributed to the abundance of homoplasies where unrelated species evolved similar traits, which makes reconstructing the evolutionary pathways of ammonoids particularly challenging. Another point is the sheer number of described species and data to be collected and standardized. The consequence is that not much is known about character evolution, evolutionary rates, loss of clades, the timing of these events, and which character states were negatively or positively selected for in which palaeoenvironmental context.
Bayesian tip-dating approaches now enable us to include stratigraphic information and continuous data into phylogenetic analyses and for this, the Ammonoida is a perfect group. The application of these methods shows that the evolution of such ‘difficult’ groups can be reconstructed, although both uncertainty and the underlying assumptions need to be considered. Hence, we plan to analyse ammonoid evolution and scientifically exploit the results to address the following questions:
1. Do previous non-quantitative evolutionary hypotheses hold? Are the currently used groups monophyletic? When did the main clades originate?
2. How did ammonoid evolutionary rates change through time? Are they a boom-and-bust clade where very few taxa survived mass extinctions but then rapidly rediversified, or did more lineages survived these extinctions?
3. Which extinction events selected for which character states? With the improved understanding of ammonoid palaeobiology, we can infer possible links with character states and selective survival.
4. A better understanding of clade origins will enable us to align evolutionary processes with macroecological events such as the Devonian Nekton Revolution and the Mesozoic Marine Revolution.
5. How did ontogenies change through ammonoid evolution? Recent studies have shown that the integration of ontogeny has successfully made the definition of ammonoid species more robust. New methods to integrate such data will improve our understanding of phylogeny, the evolution of reproductive strategies, and dimorphism.
6. Can we gain methodological insights by applying Bayesian phylogenetics to a stratigraphically densely sampled empirical dataset such as the Ammonoida? Due to their excellent fossil record, ammonoids are an ideal test group to address such methodological questions. We thus aim to establish ammonoids as a model organism to complement studies currently based on simulations and less fossil-rich clades.
This topic is multidisciplinary requiring an international collaborative effort. In addition, ammonoids occur in outcrops and collections of many countries, making the inclusion of an international team mandatory. Our team of 21 colleagues, who agreed to collaborate, shows that there is a strong need in our research community for a robust and up-to-date phylogeny of ammonoids, which would then become the basis for many future research projects.

Keywords

Ammonoida, Bayesian, parsimony, phylogeny, dimorphism, Devonian, Carboniferous, Permian, Triassic, Jurassic, Cretaceous