Abstract Detail

Systematics

Struwe, Lena [1], Setubal, Robberson [2], Frasier, Cynthia [3], Molina, Jeanmaire [4].

A Toxic Story: Phylogeny and Classification of Strychnos (Loganiaceae).

Strychnos is the most well-known and speciose genus in Loganiaceae (Gentianales) with over 200 shrub, tree, or liana species distributed throughout the worldwide tropics. It is an important genus both ethnobotanically and ecologically, and famous as the source of indole alkaloids such as strychnine, brucine, etc., used for such varied activities as fish poisoning, murder, arrow poisons, water cleaners, and modern medical drug development. No detailed phylogenetic study has been made of the whole genus and its close relatives until now. We reconstructed the phylogenetic relationships of Strychnos and its relatives in Loganiaceae using the nuclear internal transcribed spacer (ITS) region and maximum likelihood analysis from an automatic alignment taking secondary structure into account. In total, 147 species were included, including 127 Strychnos accessions (representing about 50% of known species), 18 other Loganiaceae species (from all tribes: Antonieae, Loganieae, Spigelieae, and Strychneae), and one outgroup (Gelsemium in Gelsemiaceae). In our study, two tribes (Antonieae and Loganieae) were strongly supported as monophyletic, as was the genera Geniostoma, Mitrasacme, Spigelia, and Strychnos. The current classification of Strychnos into 12 sections is over 50 years old and therefore pre-phylogenetic. Only a few sections and subsections were recovered as monophyletic: Aculeata, Breviflorae subsection Eriospermae, Phaeotrichae (monotypic), and Spinosae. The large and polymorphic sections Breviflorae, Penicillatae, Rouhamon, and Strychnos were all grossly para- or polyphyletic in our results, indicating a dire need for a new infrageneric classification of Strychnos. Biogeographic results indicate that large clades are restricted to whole continents, and there has been infrequent dispersal or vicariance between continents. There is a basal split between an American clade and the rest of the genus (forming a mostly African clade). Within the mostly African clade, there are many African subclades, plus several subclades with species from Madagascar. Within the mostly African clade, there are two tropical Asian clades, and one dispersal to northernmost Australia from an African clade. There appears to have been two independent back-dispersals to tropical America from the mostly African clade, both resulting in large neotropical species radiations. This indicates that Neotropical Strychnos species and lineages are likely to be of highly variable ages and ancestries, and that the taxonomically most diverse group of Strychnos are to be found in Africa. Future planned work includes reclassifications of sections and identification of morphological and chemical synapomorphies to fully understand the evolution of this important genus.

1 - Rutgers University, Ecology, Evolution And Natural Resources, 59 Dudley Road, Foran Hall Rm 237, New Brunswick, NJ, 08901, United States
2 - Rio de Janeiro Botanical Garden, Rua Pacheco Leão, 915, , Rio de Janeiro, RJ, 22460-030 , Brazil
3 - Department of Conservation Genetics, Omaha's Henry Doorly Zoo and Aquarium, 3701 S. 10th St, Omaha, NB, 68107, US
4 - Department of Biology, Long Island University-Brooklyn, 1 University Plaza, Brooklyn, NY, 11201, US

Keywords:
Loganiaceae
Gentianales
Biogeography
Systematics
molecular evolution
vicariance
dispersal
classification.

Presentation Type: Oral Paper
Session: 45, Systematics IV--Caryophs to Euasterids 2
Location: 111/Mayo Civic Center
Date: Wednesday, July 25th, 2018
Time: 2:15 PM
Number: 45004
Abstract ID:318
Candidate for Awards:None