The relationship between body mass and locomotion in rodents.
“The relationship between body mass and locomotion in rodents.
Anas Tantash. The Ohio State University Marion, OH.
Email: tantashan@gmail.com.
Spring-Undergraduate-Research-Festival-Anas-Tantash
Forty percent of living mammal species in the world are rodents. In addition to this incredible species diversity, rodents also exhibit immense morphological variation. The smallest rodents are only a few grams while the largest rodent on the planet, the capybara, weighs over 60 kilograms. Rodents also display great diversity in the way they move around the landscape. Some rodents are burrowers, some live in trees, some can jump incredible distances, others can swim, glide, or run. Although the nature of physics and physiology suggest that that there are constraints on the size of rodents associated to their locomotion, this hypothesis remains untested. I am investigating the relationship between body mass and locomotion in rodents and quantifying their possible co-evolution.
I am using species averages for body mass reported in the literature to investigate differences in mean body mass and disparity across locomotory categories (including arboreal, semi-aquatic, ricochetal, fossorial, terrestrial, semi-fossorial, gliding, and cursorial species). My dataset includes living species of rodents from the entire globe as well as fossil species from North America that help represent ecomorphologies now extinct (e.g., the bear-sized beavers that used to live in Ohio). My current dataset of 413 species of rodents ranges in body mass from 6.43 grams to 47,500 grams. My pilot analyses show that cursorial rodents have the highest mean body mass of any locomotory category at 8,183 grams. Ricochetal (bipedal jumping) rodents have the lowest mean body mass (155 grams). They are not significantly different from terrestrial rodents; both groups are significantly smaller than the other locomotory categories. Gliding rodents overlap in size with all but the ricochetal and terrestrial categories despite their unique locomotory constraints. Ongoing work associating these body size and locomotion data to a phylogenetic framework will enable the consideration of evolutionary dynamics. I am also currently expanding the dataset for this analysis and will be including analyses of standard deviation in addition to comparisons of means.”
Anas,
Your poster looks great and your narration was very professionally done. I wanted more of course, but it’s the nature of the format that we can’t monopolize your time like we might at a traditional poster. You spent some time on this, but I was curious about niche space availability. The kangaroos suggest that medium to large ricochetal mammals are possible but they are almost absent in rodents. Meanwhile, you get large cursorial rodents in South America but nowhere else. How much do you think relates to what sort of competition rodents ran into as they were radiating?
Ultimately, I think there are some factors relating to the level competition rodents experienced over time. The unique isolation of South America for instance, might have played a part in reducing the competition rodents encountered. There are very few large herbivores found in South America and because of this, large cursorial rodents such as the Capybara are left to flourish. This lack of competition allows rodents to fill an “ecological hole” created by the shortage of larger herbivores.