James Leonard McDaniel
Published: 2019
Total Pages: 0
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Remarkably, subtribe Pleurothallidinae (Orchidaceae) accounts for 15-20% of total orchid diversity with>4,000 species in 29 genera. One of the most extraordinary genera of 'pleurothallids' is Porroglossum, which accounts for 54 described species that are distributed throughout Andean cloud forests in South America. In actuality, the flowers of Porroglossum set it apart from nearly all other 'pleurothallids' because the labellum, when physically stimulated, actively snaps inward thrusting pollinators against the column to ensure pollination. Porroglossum is also an exceedingly young plant lineage that arose between approximately 3 and 4 million years ago. Despite the evolution of an elaborate pollination trap, little is known about the biology of Porroglossum, which presents unique opportunities for evolutionary studies. As a result, we present the first phylogenetic study of the genus Porroglossum. By sequencing multiple genetic markers, we achieve good resolution and support, which allows us to propose a revised subgeneric classification system incertae sedis. Additionally, we found that individual gene trees vary in terms of resolution and statistical support. In particular, we note that species P. sergioi and P. teaguei switch clades when comparing the plastid and nuclear datasets, which suggests potential hybridization when coupled with geographic data that indicates sympatry among their proposed parents. Moreover, we employ Next-Generation Sequencing, in the form of genotyping-by-sequencing, to address phylogenetic uncertainty that stems from the Sanger sequencing study. The GBS study illustrates the importance of extensive parameter testing when reconstructing the evolutionary history of non-model organisms with de novo assembled loci. Specifically, parameter testing helps maximize the recovery of phylogenetically informative characters while reducing the amount of sequencing errors and paralogs in the final dataset. This results in unprecedented resolution thereby resolving deep internal nodes as well as interspecific relationships within Porroglossum. Furthermore, we present the first kinematics study in a phylogenetic context that addresses the active floral snap-trap. Continuous traits appear to be strongly correlated with the evolutionary history of Porroglossum. Within the genus, we note clades with delayed and undelayed snap-traps that take multiple minutes or only a few seconds to close respectively. Lastly, snap-trap traits appear to be correlated with elevation.