Abstract Detail

Speciation Mechanisms in Plants

Spigler, Rachel [1], Frazee, Lauren [2], Rifkin, Joanna [3], Grant, Alannie-Grace [4], Maheepala, Dinusha [5], Litt, Amy [6], Wright, Stephen [3], Kalisz, Susan [4].

New genomic resources and comparative analyses pave the way for understanding the association between selfing and species divergence in Collinsia .

The evolutionary shift from outcrossing to selfing is one of the most common evolutionary transitions within the Angiosperms. Well studied in its own right, it is also becoming recognized as a potentially important mechanism promoting speciation, despite its reputation as an evolutionary dead end. Selfing can serve as an efficient barrier to gene flow, allowing for population divergence, and reduce pollen transfer between species, reinforcing species’ boundaries in sympatry. The self-compatible genus Collinsia (Plantaginaceae) provides an extraordinary study system in which to investigate the links between selfing and speciation. Within the genus are seven pairs of sister species that diverge in selfing rate, representing independent, parallel transitions from outcrossing (or ‘mixed mating’) to high selfing rates. Sister species pairs also diverge in floral morphological and developmental traits. This includes reduced flower size, pollen production, and floral lifespan in selfing species relative to their outcrossing sister species, consistent with what is known as the “selfing syndrome”. Key to both distinguishing the selfing rate and avoiding hybridization between the often sympatric and cross-compatible species pairs is the timing of selfing, strongly related to the timing of stigmatic receptivity. Identification of the mechanistic evolutionary genomic processes driving species divergence associated with selfing syndrome evolution has been limited by the absence of genomic resources, until now. We present a high quality, de-novo genome assembly for the highly selfing species C. rattanii. To begin addressing the genomic and molecular basis of selfing syndrome developmental shifts, including the timing of selfing, we evaluate and contrast patterns of gene expression from floral transcriptomes across three stages of bud development for C. rattanii and its outcrossing sister species C. linearis. We find a common pattern among differentially expressed genes: lower expression levels that are more constant across bud development in C. rattanii relative to C. linearis. Transcriptional regulation of enzymes involved in pollen formation, specifically in early bud development, may influence floral traits that distinguish selfing and outcrossing Collinsia species through pleiotropic functions. Results of this work not only provide a proof of concept but point towards genes of interest that can be compared across the genus.

1 - Temple University, Biology, 1900 N 12th Street, Philadelphia, PA, 19122, United States
2 - Temple University, Philadelphia, PA, 19122
3 - University of Toronto, Toronto, ON, CA
4 - University of Tennessee - Knoxville, Knoxville, TN, USA
5 - University of California, Riverside, riverside , CA, usa
6 - University Of California, Riverside, Botany And Plant Sciences, 900 University Avenue, Riverside, CA, 92521, United States

Keywords:
selfing rate
Speciation
gene expression
parallel evolution
genomics
floral evolution.

Presentation Type: Colloquium Presentations
Session: C09, Speciation Mechanisms in Plants
Location: /
Date: Thursday, July 22nd, 2021
Time: 3:45 PM(EDT)
Number: C09009
Abstract ID:391
Candidate for Awards:None