Molecular Phylogeny of the Genus Houstonia and Allies in Rubiaceae

<p>Houstonia (Rubiaceae) is a strictly North American genus of 24 species distributed from Mexico, throughout the United States, up to Canada. Houstonia has proven to be a taxonomically difficult genus since the Linnaean description of Houstonia and the related genera: Hedyotis and Oldenlandia in 1753. For over 250 years botanists have lumped and separated Houstonia from Hedyotis and Oldenlandia based on various morphological characters. The most recent circumscription of Houstonia (Terrell 1996) separated the genus into two subgenera with each subgenus containing two sections. Nuclear (ITS) and plastid (trnL-F, rps16) DNA sequences were used to build a molecular phylogeny depicting relationships within Houstonia and among the closely related genera Stenaria and Stenotis, all of which used to be considered Hedyotis. Separate and combined datasets show Stenaria is nested within the Houstonia lineage and therefore Houstonia, as currently circumscribed, is not a monophyletic lineage. These results disagree with the use of crateriform seeds to distinguish Houstonia (crateriform seeds) from Stenaria (non-crateriform seeds). It appears the most useful characters to define this group are the loss of chromosomes through the major clades as the Houstonia-Stenaria lineage radiated north and east in North America. Descending aneuploidy has been accompanied by slight modifications of the pollen aperture types from a simple endoaperture in Stenotis referred to as colporate type A with modifications in Houstonia-Stenaria resulting in compound aperture types referred to as colporate type B and colpororate.</p>

Name thesis:degree_name

Master of Science (MS)

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Biological Sciences

Year dc:date.available

2015

Author dc:creator

• Shanks, Hunter Lee

Contributors dc:contributor

• Lytton Musselman
• Tatyana Lobova
• Rebecca Bray

• Houstonia
• Phylogenetics
• Rubiaceae
• Biology
• Botany

Statement dc:rights

• <p>In Copyright. URI: <a href="http://rightsstatements.org/vocab/InC/1.0/">http://rightsstatements.org/vocab/InC/1.0/</a> This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).</p>

Identifier

9781339040905

OAI identifier oai:identifier

oai:digitalcommons.odu.edu:biology_etds-1002