Abstract Detail


Freudenstein, John [1], Broe, Michael [2].

Resolving a key node in Monotropoideae (Ericaceae); dissecting the problem of conflicting signal.

Monotropoideae are a small group of wholly mycoheterotrophic herbaceous plants with a center of diversity in the western United States, but with a few widely distributed species.  Morphologically, the genera are strikingly distinct and they often differ in color.  Our previous studies have shown that this subfamily is sister to Arbutoideae, a group of shrubs and small trees that is also centered in the American southwest.  Our previous work, as well as that of others, has shown a clear phylogenetic pattern across the subfamily, with Pterospora and Sarcodes sister to the remainder of the genera, then with Pleuricospora sister to two main clades, one comprising the “white” monotropoids (Monotropa, Monotropsis, Monotropastrum) and the other Hemitomes, Allotropa, Hypopitys and Pityopus.  Most of these relationships shown high levels of branch support.  The most difficult relationship in the tree to resolve has been that of Allotropa and Hemitomes.  Very distinct morphologically, different data sets and methods of analysis yield varying perspectives on their relationships.  The competing alternatives are (1) Allotropa and Hemitomes as sister to each other, and (2) the genera as successive sisters in either order to Hypopitys + Pityopus.  Oftentimes, ambiguously resolved clades are on short branches relative to others in a tree, but in this case the branches are similar in length to those resolved with strong support.  We employed short-read massively parallel sequencing to obtain sequences from multiple nuclear loci as well as to assemble whole plastomes, which were then subjected to phylogenetic analysis.  Analysis of 70 nuclear loci when concatenated and under ML gives 100% bootstrap support for Allotropa + Hemitomes, but concordance factors indicate significant underlying support for the alternatives.  A coalescent approach, using SVDquartets shows equal support for the three possible alternatives.  Whole plastome analysis reveals conflicting results depending on which loci are included, with some groups of loci strongly supporting each of the alternatives.  The pattern that emerges here is that, for this particular relationship, there is significant support for alternative topologies based on molecular data, which could indicate gene exchange that persisted after lineage separation.  Morphologically, Hemitomes shares at least one distinctive anther synapomorphy with Hypopitys and Pityopus, which argues for a particular resolution. 

1 - Ohio State University, Evolution, Ecology, and Organismal Biology, 1315 Kinnear Road, Columbus, OH, 43212, United States
2 - Ohio State University, Evolution, Ecology and Organismal Biology, Columbus, OH, 43210, USA

phylogenetic signal.

Presentation Type: Oral Paper
Session: SYS2, Systematics II: Rosids part B to Basal Asterids
Location: Virtual/Virtual
Date: Tuesday, July 28th, 2020
Time: 2:00 PM
Number: SYS2007
Abstract ID:770
Candidate for Awards:None

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