Ecology and Molecular Phylogenetics of <i>Hydnora</i> (Hydnoraceae) in Southern Africa

<p>The Hydnoraceae are a clade of root holoparasitic angiosperms that contain two small genera, <em>Hydnora</em> and <em>Prosopanche</em>. This study, focused on <em>Hydnora</em>, presents novel data regarding the pollination biology, germination ecology, parasite-host nutritional relationships, and the molecular systematics of this group. Experimental addition of the primary pollinator, <em>Dermestes maculatus</em> to <em>Hydnora africana</em> chamber flowers demonstrated beetle imprisonment during the carpellate stage. Changes in the inner surfaces of the androecial chamber allowed beetle escape after pollen release. Most beetles escaped, dusted with viable pollen, three days after pollen release. To investigate germination ecology, aqueous root extracts of host and non-host <em>Euphorbia</em> spp. were applied to seeds of <em>Hydnora triceps</em> which germinated only in response to root extracts of its exclusive host, <em>Euphorbia dregeana</em>, and not for co-occurring non-host <em>Euphorbia</em> spp. This pattern of host specific germination suggests that germination response to host-root cues may be responsible for host partitioning. There are large gaps in our understanding of holoparasitic plant-host nutrient relationships and the mechanisms of solute uptake. Transdermal water loss, parasite-host mineral relationships, and heterotrophy were evaluated for <em>Hydnora </em>. Transdermal water loss in <em>Hydnora</em> ranged from 0.14±.02 to 0.38±.04 mg cm^-2 hr^-1, comparable to transpiration rates recorded for xerophytes. Concentrations of P and K were higher in <em>Hydnora</em> relative to their CAM (Crassulacean acid metabolism) hosts; other mineral concentrations were significantly lower in the parasite or were not different. Stable isotope fractionation in host tissues dictated significant differences between parasite and host δ ¹³C signatures. A phylogeny of the Hydnoraceae was generated using plastid (<em>rpoB</em>) and nuclear ITS (internal transcribed spacer) DNA sequences. The analyses supported the monophyly of <em>Hydnora</em> and <em>Prosopanche</em>, their relationship as sister genera, and validated subgeneric sections of <em>Hydnora</em>. Optimization of the character of host preference suggests the Fabaceae as the ancestral state of <em>Prosopanche</em> and <em>Hydnora</em>. A well resolved Hydnora clade parasitizing Fabaceae was resolved as sister to a clade parasitizing exclusively <em>Euphorbia</em>, indicating a single host shift. In order to examine the specific limits of <em>H. africana</em> phylogenetic and morphological data were compared. In the section <em>Euhydnora</em>, floral morphometric data was congruent with phylogenetic data, revealing three cryptic taxa within <em>Hydnora africana sensu lato, Hydnora africana, Hydnora longicollis</em>, and a new <em>Hydnora</em> species.</p>

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Biological Sciences

Year dc:date.available

2009

Author dc:creator

• Bolin, Jay Francis

Contributors dc:contributor

• Lytton J. Musselman
• Rebecca D. Bray
• Erika Maass
• Timothy Motley

• Hydnora triceps
• Parasitic plants
• Pollination
• Botany
• Evolution
• Plant Biology

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

9781109566345

OAI identifier oai:identifier

oai:digitalcommons.odu.edu:biology_etds-1053