#  Hillery Metz’s Thesis Defense. 

 



####  calendar\_today Date and Time 

 **April 29, 2015** 

 10:30AM - 10:30AM EDT 

####  pin\_drop Location 

 **HUH Seminar Room**  



 

 



 

Please join us on Wednesday, April 29th, at 10:30 AM in the HUH Seminar Room for Hillery Metz’s thesis defense.

**Title: The genetic basis of behavior: burrow construction in deer mice (genus *Peromyscus*)**

**Abstract**

Understanding how complex, adaptive behavior evolves is a major goal of biological research. Phenotypic differences between closely-related species often arise due to evolution by natural selection and can be a powerful resource for understanding biological diversity and its mechanistic underpinnings. In this dissertation, I capitalize on striking behavioral differences between two interfertile sister species of *Peromyscus* rodents. I pursue the proximate mechanisms underlying this behavioral adaptation by investigating both the ontogeny and genetics of innate differences in burrow construction behavior in *Peromyscus polionotus* and *P. maniculatus.*

In Chapter 1, I compare the ontogeny of burrow construction behavior of *Peromyscus polionotus* and *P. maniculatus* across early development. I find that *P. polionotus* begins burrowing precociously (as early as 17 days of age) compared to *P. maniculatus* (27 days of age), despite *P. polionotus* being physically smaller and less active in a wheel running assay. Furthermore, juvenile *P. polionotus* constructed long burrows complete with species-specific escape tunnels. Interspecific cross-fostering did not alter the developmental trajectory of either species, indicating that these differences are innate. Moreover, F1 hybrids followed the behavioral ontogeny of *P. polionotus*, indicating that precocious burrow construction segregates in a *P. polionotus*-dominant manner. Finally, I show that a quantitative trait locus (QTL) associated with adult tunnel length in these species is predictive of precocious digging in recombinant F2 hybrids, demonstrating that either a single pleiotropic locus or a group of tightly-linked genes control behavioral differences across life stages in *P. polionotus*.

 In Chapter 2, I dissect the genetic architecture of this complex behavior in adult animals using an experimental cross. By introgressing the burrow architecture of *P. polionotus* into the genetic background of *P. maniculatus,* I analyze the underlying genetic architecture of differences in burrowing behavior, and show that escape tunnels are likely a threshold trait. Finally, I use a novel image-based analysis to collect measurements of burrow shape and demonstrate the utility of a more rigorous measurement of extended phenotypes.

 Finally, in Chapter 3, I combine two forward-genetics approaches—QTL mapping and transcriptome analysis—to nominate specific candidate genes for the differences in burrowing behavior between *P. polionotus* and *P. maniculatus*. Using a large advanced backcross mapping population (n=751), I detect five QTL contributing to differences in burrow architecture between these species: three loci for entrance tunnel length variation, and two loci for escape tunnel length. In the transcriptome study, I focus on gene expression in F1 hybrids to detect allele-specific expression (ASE), as ASE in an F1 hybrid indicates *cis*-regulatory differences between the parental lineages. I find widespread bias favoring expression from the *P. polionotus*-allele in F1 hybrid brains, which may be a molecular reflection of *P. polionotus*-like burrowing behavior of hybrids. Finally, I use ASE to nominate candidate genes within the detected QTL regions, and find genes related to behavioral disorders, circadian rhythms, and activity patterns; these genes represent promising candidates for future functional studies.



 

 



 

 

 Share on:- [     Facebook ](#)
- [     Twitter ](#)
- [     Linkedin ](#)
 


 Save: [ Add to calendar calendar\_today ](https://hoekstra.oeb.harvard.edu/node/576511/event-feed.ics)  Copy link link