Emily Jacobs-Palmer | Search bioRxiv

bioRxiv2016

The genetic basis and fitness consequences of sperm midpiece size in deer mice

An extraordinary array of reproductive traits vary among species, yet the genetic mechanisms that enable divergence, often over short evolutionary timescales, remain elusive. Here we examine two sister-species of Peromyscus mice with divergent mating systems. We find that the promiscuous species produces sperm with longer midpiece than the monogamous species, and midpiece size correlates positively with competitive ability and swimming performance. Using forward genetics, we identify a gene associated with midpiece length: Prkar1a, which encodes the R1 regulatory subunit of PKA. R1 localizes to midpiece in Peromyscus and is differentially expressed in mature sperm of the two species yet is similarly abundant in the testis. We also show that genetic variation at this locus accurately predicts male reproductive success. Our findings suggest that rapid evolution of reproductive traits can occur through cell type-specific changes to ubiquitously expressed genes and have an important effect on fitness.

Evolutionary Biology↗

bioRxiv2014

Direct gamete sequencing reveals no evidence for segregation distortion in house mouse hybrids

Understanding the molecular basis of species formation is an important goal in evolutionary genetics, and Dobzhansky-Muller incompatibilities are thought to be a common source of postzygotic reproductive isolation between closely related lineages. However, the evolutionary forces that lead to the accumulation of such incompatibilities between diverging taxa are poorly understood. Segregation distorters are an important source of Dobzhansky-Muller incompatibilities between Drosophila species and crop plants, but it remains unclear if the contribution of these selfish genetic elements to reproductive isolation is prevalent in other species. Here, we genotype millions of single nucleotide polymorphisms across the genome from viable sperm of first-generation hybrid male progeny in a cross between Mus musculus castaneus and M. m. domesticus, two subspecies of rodent in the earliest stages of speciation. We then search for a skew in the allele frequencies of the gametes and show that segregation distorters are not measurable contributors to observed infertility in these hybrid males, despite sufficient statistical power to detect even weak segregation distortion with our novel method. Thus, reduced hybrid male fertility in crosses between these nascent species is attributable to other evolutionary forces.

Evolutionary Biology↗