Link to Audio : Scarpitti_SURF
The Link between Ecology and Auditory Bulla Morphology in Rodents: Applications to the Fossil Record
Abstract:
Rodentia is the most species-rich order of mammals. This taxonomic diversity is mirrored by their ecological diversity; rodents can be found living in almost all environments from tropical forests to deserts. Such ubiquitousness is enabled by many evolutionary adaptations, including some concentrated in the sensory systems. Hearing is essential to survival; it enables predator evasion, prey detection, and conspecific recognition. It is also constrained by the surrounding physical environment. As such, I hypothesize the hearing system of rodents to be ecology-specific. Although the auditory apparatus of select species has been studied, the link between tympanic bulla morphology and ecology has never been investigated across a broad swath of species. Yet, this avenue of research offers the potential to explore the ecological affinities of many fossil species whose skeleton is unknown. I here present a comparative study of bullar morphology in rodents across locomotory ecologies. I used geometric morphometrics to quantify the shape of the auditory bulla of 203 specimens of modern rodents representing 94 species from 17 families and four different locomotory modes. I placed landmarks and semi-landmarks on photos of the ventral and lateral views of each specimen to capture characteristics of bullar inflation and external auditory meatus extension. The results of my principal component analyses and canonical variate analyses demonstrate an association between bullar morphology and locomotion in rodents, particularly in surface-dwelling species. Overall, fossorial rodents have kidney-shaped bullae associated to an extended auditory meatus (EAM) whereas arboreal and gliding rodents have inflated bullae and a very short EAM. Terrestrial and semi-fossorial species are intermediate in morphology. The classification phase of the analysis correctly classified 76.8% of terrestrial, semi-fossorial, arboreal, and fossorial. I used this framework to investigate the ecology of select fossil rodents with known locomotory inferences from independent proxies. My results are consistent with published data and further strengthen my approach, which I used to reconstruct the locomotion of extinct rodent species that lack skeletons.
Erica,
This research is really interesting and the fact that your results are consistent with published data definitely means that your approach is very effective! Overall, I think your poster presentation looks good! However, I understand that you may have many graphics that you need to include, but I think maybe adding in 2 discrete lines to separate the research question column and the graphics and also the discussion would make it easier to distinguish the different columns. Overall I think the research was done very well!
Congratulations Erica on a job well done. The poster and the research are really interesting. I agree with Emily that maybe the images/graphs could be a little smaller, leaving more space for your conclusions/discussion. Be well.
Great job Erica! Really interesting to explore ecological aspects of fossil species whose skeleton is unknown. You’ve demonstrated the value of this approach and outlined a nice path forward for future work.