Abstract Detail

Systematics

McDaniel, James [1], Cameron, Ken [1].

The Power of Movement in Orchids, a Kinematics Study of Porroglossum (Pleurothallidinae).

After publishing On the Origin of Species, Charles Darwin set out to provide evidence for his theory of evolution by natural selection which led him to become fascinated by the power of movement in plants. In particular, Darwin had a strong interest in the various types of climbing plants, leaves exhibiting sleep movements, and insectivorous plants exhibiting fast-action snap-traps. Within Orchidaceae, Darwin even labeled Catasetum as “the most remarkable of all orchids” due to the mechanism by which male flowers of the genus eject their pollinia in response to a physical stimulus. Had Darwin known about the orchid genus Porroglossum, surely he would have considered these small plants of subtribe Pleurothallidinae equally remarkable because physical stimulation of the flower’s labellum causes it to actively snap inward thrusting pollinators against the column. Porroglossum is composed of 53 described species, most of them endemic to Ecuador, that are distributed throughout the Andean cloud forests of South America. In August of 2014 and 2015, we recorded high-speed videos (60fps) of the active, floral snap-trap at the orchid nursery Ecuagenera in Gualaceo, Ecuador. For each video, we included a scale bar (e.g., a ruler), applied a single stimulus to the callus of the labellum, and did not cease recording until the labellum of the flower was fully closed. As a result, we obtained >900 videos spanning 30 species of Porroglossum (>20 samples per species). By utilizing the program Tracker, we were able to calculate the average time to snap-trap closure for each species as well as the average velocity and acceleration of the snap-trap for each species. Furthermore, we implemented statistical methods in R to map the aforementioned continuous traits for each species onto a fully-resolved phylogenetic tree produced through genotyping-by-sequencing and calculate phylogenetic signal. By doing so, we documented strong phylogenetic signal when using both Pagel's λ (λ = 1.0840, p = 0.0014) and Blomberg's K statistic (K= 1.7001, p = 0.0027) indicating that closely related species resemble each other more than expected by chance in relation to time, velocity, and acceleration. Graphically, the same results were documented where all of the species of a clade either exhibit warm colors (indicating fast-action snap-traps) or cool colors (indicating slow snap-traps) with the most rapidly moving snap-traps evolving independently in the Porroglossum phylogeny on more than one occasion.

1 - University Of Wisconsin - Madison, Botany, 430 Lincoln Drive, Madison, WI, 53706, USA

Keywords:
Orchidaceae
Pleurothallidinae
Genotyping by sequencing (GBS)
kinematics
phylogenetic signal
R.

Presentation Type: Oral Paper
Session: 20, Basal Dicots/Monocots part A (Asparagales)
Location: 200/Savannah International Trade and Convention Center
Date: Tuesday, August 2nd, 2016
Time: 8:30 AM
Number: 20003
Abstract ID:402
Candidate for Awards:None