Abstract Detail

Systematics

Bentz, Philip [1], Harkess, Alex [2], Popecki, Margot [3], Starr, Dakota [1], Leebens-Mack, Jim [4].

Timing of evolutionary origins of dioecy in Asparagus L.

Sex chromosomes have evolved independently in various lineages across the Angiosperm phylogeny. Though the evolution of separate sexes (i.e., distinct male and female individual organisms, or dioecy) has occurred multiple times in various Angiosperm lineages, it remains a relatively rare phenotype—most flowering plants are hermaphroditic. Investigating young sex chromosomes offers opportunities to gain insight into fundamental evolutionary questions regarding the evolution of sex. The genus Asparagus L. (Asparagaceae) represents an ideal system for studying the evolution of sex; Asparagus is mostly composed of hermaphroditic lineages, but also contains several dioecious lineages. Phylogenetic and phylogenomic analyses suggest either two origins of dioecy, or a single origin and at least one subsequent loss of dioecy within Asparagus. Dioecy has been hypothesized to have arisen somewhat recently in Asparagus, given the limited divergence between cytogenetically identical X and Y chromosomes in garden asparagus (A. officinalis). Here we report for the first time molecular divergence time estimates for the origins of the genus Asparagus and shifts from hermaphroditism to dioecy within the genus. We sequenced the plastomes of 10 Asparagus species and generated a time-calibrated phylogeny including protein-coding genes from 95 monocot plastomes. Results from the plastome data provide support for the origin of Asparagus to have occurred roughly 12.08 (95% HDP=5.95-24.51) MYA. Additional results from these data, along with phylogenomic analyses of nuclear gene-capture data, provide strong support for either two recent origins of dioecy approximately 2.99 (95% HDP=1.23-7.3) and 2.81 (95% HDP=1.08-7.3) MYA within Asparagus, or a single origin of dioecy (~2.99 MYA) followed by at least one loss (~2.81 MYA). Our findings provide further evidence for the relatively young age of dioecy and sex chromosomes within Asparagus. Moreover, our work illustrates the value of comparative genomic analyses for elucidating genetic processes contributing to the origin and early evolution of sex chromosomes.

1 - University Of Georgia, Department Of Plant Biology, 120 Carlton Street, Athens, GA, 30602, United States
2 - Auburn University, Department of Crop, Soil, and Environmental Science, 201 Funchess Hall, Auburn, AL, 36849, USA
3 - University of Georgia, Department of Genetics, 120 Green Street, Athens, GA, 30602, USA
4 - University Of Georgia, Plant Biology, 2101 Miller Plant Sciences, Athens, GA, 30602, United States

Keywords:
Asparagaceae
Dioecy
phylogeny
Asparagus
genomics
divergence time estimation
evolution
phylogenomics
comparative genomics
monocots
dioecious
sex chromosomes
genetics.

Presentation Type: Oral Paper
Session: SYS3, Systematics III: Cooley Award presentations
Location: Virtual/Virtual
Date: Wednesday, July 29th, 2020
Time: 11:45 AM
Number: SYS3008
Abstract ID:425
Candidate for Awards:None