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We are evolutionary biologists with broad interests in the genetic and epigenetic basis of mammalian behavior, the process of speciation, and sex chromosome evolution. These research areas are connected by our interest in conflict, whether as a source of reproductive incompatibilities between species, a driver of evolution on sex chromosomes, or a modulator of molecular interactions between individuals. We integrate genomics and classical genetics with crossing experiments and behavioral assays.

Current and Recent Projects

Sex chromosome evolution in voles

Voles in the genus Microtus have exceptionally high rates of karyotypic evolution that include the sex chromosomes. 

We discovered that the creeping vole (Microtus oregoni) has lost an independently segregating Y chromosome. Instead, the sex chromosome system comprises two X-like chromosomes - one maternally transmitted but present in male somatic cells and the other male-specific - both of which carry a largely intact copy of the ancestral Y chromosome fused to one end (Couger et al. 2021). This means that male creeping voles are exposed to an X chromosome that can only respond to selection in females and females are exposed to a full complement of previously male-limited genes, including multiple functional copies of Sry.

Sex chromosome constitution of female (L) and male (R) Microtus oregoni in a) somatic and b) germline cells.

We are currently studying the gene regulatory consequences of these evolutionarily recent changes in sex chromosome constitution.


Upcoming work includes comparative analysis of sex chromosome evolution in the North American clade that includes M. oregoni.

The effects of placental dysregulation on maternal behavior and neural gene expression

We used a cross between the house mouse (Mus m. domesticus) and the Algerian mouse (Mus spretus) to study the effects of abnormal placental expression on mothers.


We found altered neural gene expression (Arévalo and Campbell 2020) and altered postpartum maternal behavior (Gardner et al. 2019) in house mouse mothers exposed to a hybrid pregnancy.

The role of imprinted genes in hybrid placental abnormalities

Hybrid placentas are oversized in one direction of the house mouse/Algerian mouse cross and undersized in the other. These opposite effects on growth are a signature of imprinted gene misexpression.

We found two imprinted genes that are strong candidates for causing structural abnormalities in the endocrine compartment of hybrid placentas, and downstream effects on maternal gene expression and behavior (Arévalo et al. 2021).

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