Abstract Detail

Systematics

Garwood, Nancy [1], Humphreys, Aelys [2], Neubig, Kurt Maximillian [3], Jordan, Kristina [4].

Evolution of Trema species in the Neotropics.

Trema Lour. (Cannabaceae) is a genus of pantropical pioneer tree species. Although many Neotropical species have been named, almost all are now included within the broadly defined T. micrantha (L.) Blume except T. cubensis Urb., T. domingensis Urb., T. integerrima (Beurl.) Standl. and T. lamarckiana (Roem. & Schult.) Blume. Reports of hybridization have not been rigorously studied. Trema micrantha is the most widespread species, ranging from Florida to Argentina, and also the most complex: its considerable morphological variability at local to regional scales has long stymied taxonomists. Our previous molecular work on Trema world-wide (Yesson et al. 2004) found that Neotropical Trema was monophyletic with respect to Paleotropical species, but that T. micrantha was not monophyletic. Here we use greatly expanded sampling of T. micrantha and congeners across their range (including T. cubensis and T. domingensis for the first time), four rather than two loci, whole plastome sequencing and morphology to examine the phylogeny of Neotropical Trema species. We test the robustness of previously identified clades of T. micrantha, determine their geographical distributions and probe species boundaries, to understand evolution of Trema in the New World. We found six well supported molecular clades, but relationships among clades were not well supported. The Hispaniola-endemic Trema domingensis is conspecific with T. integerrima, from Central and South America. Trema lamarckiana, T. cubensis and T. integerrima (including T. domingensis) are each monophyletic. Within T. micrantha, we found strong support for three clades that are not sister to each other. An early diverging lowland clade (A) grows at elevations < 1000 m in the Caribbean, and Central and South America. A late diverging lowland clade (B) has a similar distribution to clade A but extends into Florida. A montane clade (C) grows at elevations mostly ≥ 1000 m in the Caribbean through South America, but is absent from Central America. (There are Trema in Central America at > 1000 m, but these are allied to clade B.) Each of the six clades can be recognized using endocarp and leaf characters. Clade B, however, still remains the most variable morphologically and least resolved molecularly. Incongruence among molecular datasets has also identified several instances of putative hybridization, both recent and ancient, which might explain the difficulty in resolving variation within clade B. Both recent and ancient hybridization would suggest a complex evolutionary history of Trema in the New World.

1 - Southern Illinois University, Life Science II, Mailcode 6509, Life Science II, Mailcode 6509, 1125 Lincoln Ave., Carbondale, IL, 62901, USA
2 - Stockholm University, Ecology, Environment and Plant Sciences, Stockholm, SE-106 91, Sweden
3 - Southern Illinois University Carbondale, Plant Biology, Carbondale, IL, 62901, USA
4 - Southern Illinois University, Plant Biology, Life Science II - Mailcode 6509, 1125 Lincoln Dr., Carbondale, IL, 62901, USA

Keywords:
phylogeny
hybridization
pioneer tree
Neotropics.

Presentation Type: Poster
Session: P, Systematics Section/ASPT Posters
Location: Exhibit Hall/Savannah International Trade and Convention Center
Date: Monday, August 1st, 2016
Time: 5:30 PM This poster will be presented at 5:30 pm. The Poster Session runs from 5:30 pm to 7:00 pm. Posters with odd poster numbers are presented at 5:30 pm, and posters with even poster numbers are presented at 6:15 pm.
Number: PSY027
Abstract ID:327
Candidate for Awards:None