Abstract Detail

Systematics

McDaniel, James [1], Cameron, Kenneth [2].

Snap-Trap Flowers of the Orchid Genus Porroglossum (Pleurothallidinae): a Kinematics Study Evaluated in the Context of Phylogenetics using GBS Data.

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. Additionally, 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, calculate phylogenetic signal, and detect evolutionary shifts in trait evolution under Ornstein-Uhlenbeck models. By doing so, we documented strong phylogenetic signal when using both Pagel's λ (λ = 1.078824, p = 6.85 x 10^-13) and Blomberg's K statistic (K= 2.509277, p = 0.0001) indicating that closely related species resemble each other more than expected by chance in relation to time, velocity, and acceleration. Furthermore, we detected three evolutionary shifts in trait evolution (a shift to slow snap-traps within a monophyletic group, a shift back to fast snap-traps for two species within the aforementioned clade, and a shift to a slow snap-trap for one species within a clade exhibiting fast snap-traps).

1 - University Of Wisconsin - Madison, Botany, 430 Lincoln Drive, Madison, WI, 53706, USA
2 - University Of Wisconsin, Department Of Botany, 154 Birge Hall, 450 Lincoln Drive, Madison, WI, 53706, USA

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

Presentation Type: Oral Paper
Session: 14, Systematics I: Basal Dicots, Monocots & Rosids
Location: Sundance 1/Omni Hotel
Date: Monday, June 26th, 2017
Time: 2:15 PM
Number: 14004
Abstract ID:385
Candidate for Awards:None