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Abstract Detail

Reproductive Processes

Pratt, Donald B. [1], Farmer, Todd [2].

Is dioecy an evolutionary dead end in Amaranthus?

Dioecy has been proposed by several authors to be an evolutionary dead end among Angiosperms based on observations that it is relatively rare and because in clades with both dioecious and cosexual species the cosexual species tend to be more numerous. Theoretical claims that dioecy is a dead end are based on two arguments, 1) that dioecy is an irreversible character state, and 2) that dioecious species have lower speciation rates and higher extinction rates than cosexual species. The genus Amaranthus consists of approximately 75 species, ten of which are dioecious. A recent phylogeny of Amaranthus (Waselkov 2013) provided the opportunity to explore the evolution of dioecy within an evolutionary context using ancestral state reconstruction and transition rate bias analyses. Both nuclear and plastid derived trees indicate multiple origins of dioecy with at least one reversion to monoecy. Transition rate tests of nDNA phylogenies support an asymmetrical rate bias in favor of reversions from dioecy back to monoecy. Although we were unable to compare speciation and extinction rates with these data, it appears that dioecy in Amaranthus is a reversible character state with an asymmetrical bias in favor of reversals to monoecy. During the last three decades two weedy dioecious species have rapidly spread and displaced many weedy monoecious species within their ranges demonstrating that dioecy is not a dead end for Amaranthus.

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1 - Stephen F. Austin State University, Box 13003 SFA Station, Nacogdoches, TX, 75962, USA
2 - Angelina College, 3500 S 1st Street, Lufkin, TX, 75904, USA

breeding system

Presentation Type: Oral Paper
Session: 30, Reproductive Processes
Location: Fort Worth Ballroom 7/Omni Hotel
Date: Tuesday, June 27th, 2017
Time: 4:00 PM
Number: 30009
Abstract ID:317
Candidate for Awards:None

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