Abstract Detail

Systematics

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

Systematics of Porroglossum (Pleurothallidinae) Orchids: An Integrative Approach to Phylogenetics, Floral Snap-Trap Kinematics, and Fragrance Analysis.

The Neotropical orchid subtribe Pleurothallidinae appears to have arisen approximately 14.2 million years ago, yet remarkably it contains >4,000 species in 29 genera that account for 15-20% of total diversity within Orchidaceae. These ‘pleurothallids’ represent a lineage that has undergone a significant acceleration of net diversification despite being young in terms of geologic time. Here, we focus on the systematics of the genus Porroglossum, which is composed of 54 described species that are distributed throughout Andean cloud forests from Venezuela south to Bolivia. Historically, inferring phylogenetic relationships among recently diverged taxa has proven to be difficult due to a lack of informative characters within commonly sequenced genetic markers as well as gene tree discordance originating from biological phenomena such as incomplete lineage sorting and hybridization. Previously, we reconstructed the evolutionary history of Porroglossum using traditional Sanger sequencing methods and recovered three highly supported clades that include: Porroglossum (94% BS), Echidnae (100% BS), and Brevisepala (100% BS); however, deep internal nodes remained unresolved as well as interspecific relationships. As a result, we explored the utility of reduced-representation genome sequencing in the form of genotyping-by-sequencing (GBS) for phylogenetic inference. Total genomic DNA from 39 species of Porroglossum and four closely related outgroups were digested using the restriction enzyme ApeKI and sequenced on an Illumina HiSeq2500 thereby generating single-end, 100 bp reads. By utilizing high-throughput computing, we tested the various core parameters of the pyRAD and Stacks pipelines before generating genomic datasets consisting of de novo assembled loci. Our resulting GBS phylogenies recovered the original three highly supported clades (Porroglossum, Echidnae, and Brevisepala) while resolving deep internal nodes and interspecific relationships. Once a robust phylogeny was established, we utilized it as a tool for addressing questions directly related to the biology of Porroglossum. In particular, we combined our modern molecular approach with high-speed videography to target the active floral snap-trap as well as fragrance analysis of floral VOCs to gain a multifaceted understanding of the evolutionary relationships within the genus. By doing so, we detected multiple evolutionary shifts in trait evolution for the snap-trap among lineages and documented strong phylogenetic signal for both Pagel's λ and Blomberg's K statistic indicating that closely related species resemble each other more than expected by chance in relation to time, velocity, and acceleration. Lastly, VOCs appear to be highly conserved within clades of Porroglossum thereby exhibiting significant phylogenetic signal which provides evidence for phylogenetic niche conservatism.

1 - UW-Madison, Botany, 430 Lincoln Drive, Madison, WI, 53706, United States
2 - 430 Lincoln Dr, Madison, WI, 53706, United States

Keywords:
Orchidaceae
Pleurothallidinae
genotyping-by-sequencing
kinematics
volatile organic compounds
phylogenetic signal
R.

Presentation Type: Oral Paper
Session: 3, Systematics I--Tracheophytes, Pteridophytes to Monocots 1
Location: 110/Mayo Civic Center
Date: Monday, July 23rd, 2018
Time: 10:15 AM
Number: 3009
Abstract ID:906
Candidate for Awards:None