Echidnas are so anatomically different from other mammals that they were thought to have last shared a common ancestor with the platypus more that 100 million years ago, while dinosaurs roamed Australia. However, analyses of DNA have shown that echidnas evolved from a platypus-like ancestor much more recently, about 20-45 million years ago (Phillips et al., Proceedings of the National Academy of Sciences, USA, 2009). Fossils records of echidnas do not appear until a few million years ago.
One possibility is that the ancestors of modern echidnas remained platypus-like until recently making the transition out of water to become terrestrial, digging insectivores. Another possibility, recently expressed by Flannery et al. (Alcheringa, 2022) is that echidnas made this transition much earlier (perhaps >30 million years ago) but it has been hidden from the fossil record because it happened in New Guinea (where fossil records are poor), following an oceanic migration from Australia to the newly forming island.
This project will test find genetic signatures in the published genomes of echidnas and platypuses to test these alternative hypotheses on the origins of echidnas.
You will identify shifts in evolutionary pressures on gene sequences that indicate functional changes from semi-aquatic to terrestrial evolution along the ancestry of echidnas. For example, genes associated with tooth formation and water-based electrosensory systems are expected to have become redundant (pseduogenes) as echidna ancestrors moved into their new ecological niche.
Computer-based phylogenetic analyses will allow you to estimate the timing of these changes, and hence test the alternative hypotheses (recent change, potentially in Australia versus more ancient change, potentially in New Guinea. You may also be able to track the sequence of evolution along the ancestry of echidnas. For example, does a spike in adaptation in genes associated with metabolism pre or post-date the loss of teeth?
Refining our understanding of:
- the timing of when platypus and echidnas diverged
- whether echidnas made their ecological transition out of water recently in Australia or long ago in New Guinea
- the sequence of evolutionary steps along the way to becoming echidnas.
Skills and experience
- familiarity with R coding, though not necessarily extensive knowledge
- basic understanding of phylogeny
- a keen interest in evolutionary biology.
You may be eligible to apply for a research scholarship.
Contact the supervisor for more information.