Orchids are not only beautiful flowering plants popular with home gardeners, they also inspire scientists interested in the study of evolution, diversity, and the complex interactions between plants, animals, fungi, and the environment.  One of the best known and cherished orchids is Vanilla - the natural source of the world's most popular flavor and fragrance.  In contrast, very little is known about the fundamental biology of the closest relatives of Vanilla.  The gradute student research supported by this award focused attention on these plants.  It used cutting-edge DNA sequencing technology to study variation among 499 genes from the nuclear genome, and used those data to reconstruct the evolutionary relationships among these orchids.  They had been a challenge to work with previously because many of them have lost their leaves and ability to conduct photosynthesis.  As a result, genes in their chloroplast genome are lost or reduced.  A second aspect of the research measured the entire DNA content (genome size) of these orchids and examined that metric across the entire orchid family - the largest plant family on Earth.  We documented the largest genome size ever recorded in orchids, and also discovered an unusal case of autotetraploidy, in which some individuals within a population have 2X the normal amount of DNA in each cell.  We consider how adaptation to particular environments and life styles may have driven the evolution of extremly large genomes in unrelated lineages of orchids and other flowering plants.  Finally, after shedding light on the evolutionary relationships and genomes of these orchids, we turned our attention to understanding the balance between form and function of some of the more interesting photosynthetic members of this group.  In particular we undertook an 'eco-physiological' approach to understanding how a rare species from New Caledonia evolved to become a climbing vine in the dark tropical rainforest (its leaves have unusual net venation), whereas its closest relatives in New Caleonia and South America retain their evolutionary baggage of net-like leaf venation but thrive in open, sunny habitats (a situation that is highly unusual).  We hypothesized that they must have a unique physiology and form to survive in this stressful environment, and conducted analyzes to evalute this.  Indeed, we found significant differences in leaf area, angle at which the leaves are oriented, leaf thickness, vein density, and niotrogen content, among others variables.  This is the first time such a study has been conducted on wild orchids, and may lead to predictions of how they may adapt to a changing climate.  

Last Modified: 08/17/2017
Modified by: Giovanny Giraldo