35 Oral - Platform Session #3 Speciation, Hybridization, and Introgression
Thursday June 09, 11:20 AM - 11:35 AM

Authors:
Elen Oneal ¹; Miguel Flores-Vergara ²; Robert Franks ²; John Willis ¹

Affiliations:
1) Duke University, Durham, NC; 2) North Carolina State University, Raleigh, NC

Keywords:
Speciation & hybridization

A fundamental constraint on organismal development and evolution – that natural selection does not lead to diminished individual viability and fertility – is encapsulated in the Dobzhansky-Muller model for the evolution of hybrid incompatibilities: substitutions of alleles that are adaptive or nearly neutral in the native genomic background of one species can be dysfunctional in the genomic background of other species, resulting in inviable and/or sterile hybrids. Evidence increasingly suggests that the fixation of incompatible alleles in divergent populations may be driven by unexpected forms of selection such as intra-genomic conflict. Parent–offspring conflict, where mothers and offspring spar over evolutionary time over the extent of maternal investment, is a pervasive feature of parent-offspring interactions, and is especially prominent when mothers mate multiply and maternal investment is substantial and allocated dynamically via a placenta-like connection between mother and developing offspring. Such conflict is thought to explain, in part, the evolution of genomic imprinting, in which alleles are differentially expressed depending upon their parent-of-origin, and which has only been detected thus far in the placental tissues and developing offspring of viviparous mammals and the seed endosperm of angiosperms. Intriguingly, misregulation of endosperm development is a prominent cause of hybrid seed failure, the most common form of postzygotic isolation in plants. Is parent-offspring conflict a major factor driving plant speciation? Unfortunately, explicitly testing this hypothesis genetically is often difficult because F1 hybrids are dead. We are able to circumvent the endosperm barrier in Mimulus species by rescuing F1 embryos prior to seed death. We use these F1s in a reciprocal backcross design to map loci contributing to hybrid seed inviability and endosperm failure and test for paternal and maternal interactions between loci. We combine our mapping results with RNA sequencing of endosperm tissue to characterize species divergence in imprinting status and regulation. Our results shed light on the role of parent-offspring conflict in driving imprinting divergence and the evolution of this common postzygotic barrier in Mimulus.