Abstract Detail

Biology of Isoetales, a colloquium in honor of Dr. W. Carl Taylor

Suissa, Jacob [1], Taylor, W Carl [2], Schafran, Peter [3], Zimmer, Elizabeth [4].

Allopolyploid and Autopolyploid speciation revealed through whole plastomes and nuclear homologues in northwestern North American Isoëtes (Quillworts).

The intractability of defining species and reconstructing a phylogeny for the genus Isoëtes has been largely attributed to a simplified morphology that yields limited characters and character states and the possible presence of multiple cytotypes. Isoëtes species are descendants of an ancient lineage dating back to the Devonian and the conserved morphology of extant Isoëtes is seen in the Triassic fossil record. This conserved morphology also creates confusion when attempting to distinguish species and determine their evolutionary history. Further complicating the resolution of Isoëtes taxa and their phylogeny is reticulate evolution that involves interspecific hybridization and whole genome duplication (WGD). Recent molecular work suggests that allopolyploidy is the main driver of this type of hybrid speciation in Isoëtes. A series of putative speciation events from a group of northwestern North American Isoëtes is used to further test this hypothesis. In this region, two basic diploid species (2n=22) I. echinospora and I. bolanderi are hypothesized to hybridize to form a sterile, diploid (2n=22) I. X herb-wagneri, which then went through a WGD to yield a fertile tetraploid (2n=44) I. maritima. Isoëtes maritima then backcrossed with I. echinospora to produce a sterile triploid (2n=33) I. X pseudotruncata. This taxon then went through a WGD to produce a fertile, hexaploid (2n=66) I. occidentalis. NextGen sequencing was used to test these hypothesized series of events. Using multiple homologues of the second intron of the LFY gene and whole chloroplast genomes, we conclude that I. maritima is an allopolyploid derived from the hybridization and subsequent WGD of I. echinospora and I. bolanderi, while I. occidentalis is an autopolyploid derived directly from I. echinospora. These data suggest that in addition to allopolyploidy, autopolyploidy may play an important role in speciation within the lycophyte genus Isoëtes.

1 - Harvard University, 1300 Centre st, Boston, MA, 02131, United States
2 - 2912 22nd St N, Arlington, VA, 22201, United States
3 - Old Dominion University, Biological Sciences, Hampton Blvd., Norfolk, VA, 23529, United States
4 - Smithsonian NMNH, Botany, P.O. Box 37102, Smithsonian National Museum Of Natural History, Washington, DC, 20013, United States

Keywords:
Isoetes
Polyploid
quillwort 
Speciation.

Presentation Type: Colloquium Presentations
Session: C05, Biology of Isoetales, a colloquium in honor of W. Carl Taylor
Location: 101/Mayo Civic Center
Date: Tuesday, July 24th, 2018
Time: 11:00 AM
Number: C05011
Abstract ID:440
Candidate for Awards:None