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February 25, 2021

5:00pm Zoom

EcoEvoPub Seminar Series
Department of Ecology and Evolutionary Biology, UCLA

" Graduate Student Presentations "

Alexa Sadier

Department of Ecology and Evolutionary Biology, UCLA, Sears Lab

Bat teeth at the cusp: finding rules for the evo-devo of serial organs

Serial organs are repeated structures that are found in all organisms. Research in the last decades have shown that they share common mechanisms for their development that explain how they can be duplicated, gained or lost, making them hot spots of evolution. Recently, the examination of these mechanisms suggest that the development of these organs follow some rules that can bias the evolution of these organs certain toward phenotypes. To study these rules, teeth are particularly interesting because they are built upon a highly conserved gene network while being one of the most diverse repeated organs in terms of morphology. I take the advantage of the ~200 species of noctilionoids bats that encompass nearly all possible mammalian diets to answer questions relative to the evolution of developmental rules. First, I will focus on the diversification of post-canine dentition in Noctilionoids that are extremely variable in terms of tooth number and shape. By combining morphometric and quantitative data from 117 adult species, I showed that the number of post-canine teeth is related to the length of the jaw and that premolar and molar proportions are independent, suggesting distinct developmental mechanisms for their formation. To get insight into these underlying mechanisms, I analyzed the development of 12 species across 8 developmental stages by µCT scan and tested markers. I also injected pregnant bats with EdU to link teeth formation to the growth rate of the jaw. Finally, I proposed a new Turing-based model to explain the development of premolars and molars rows. My data reveal that the premolar and molar rows are established by two independent signaling mechanisms and that teeth number and size is linked to the local growth rate of the jaw.

Conner Philson

Department of Ecology and Evolutionary Biology, UCLA, Blumstein Lab


Consequences of social architecture for mass gain rate in an alpine hibernator

Repeated interactions between individuals form social groups. These groups are complex systems, dynamic in their nature and pattern of interaction. Work across biological systems has explored the fitness consequences of dyadic interactions and how variation in these interactions alter the structure of social groups. However, less work has explored the feedback between a social group and the individuals who comprise it. Mapping the relationship between social network architecture – specific attributes of the structure of a social group – and individual fitness correlates is important to understanding the consequences of social behavior. For hibernating species, such as the yellow-bellied marmot (Marmota flaviventer), gaining adequate mass rapidly leading up torpor is a vital for survival. Therefore, I explored the association between social architecture and individual marmot mass gain rates at the Rocky Mountain Biological Laboratory in Colorado. Social networks were constructed from 43,362 behavioral observations of 1,350 individuals in 132 unique social groups from 2002 to 2018. Using linear mixed models, we found that individuals residing in more connected and tightly knit social groups tended to gain proportionally less mass. However, living in a socially homogeneous group was associated with greater mass gain. These relationships between social architecture and mass gain were highly dependent on an individual’s age, sex, and geographic location. Namely, as groups became more integrated, yearlings, females, and individuals living in a less harsh environment tended to gain proportionally more mass. These results show how the architecture of the social group an individual resides in has consequences for a key fitness correlate, depending on an individual’s age, sex, and environment.