Orchidaceae

With over 25000 species, the orchid family is astonishingly diverse.  This research focuses on the relationships and evolutionary patterns of orchids, especially in the Neotropics.  To date, we have developed detailed preliminary phylogenetic work for multiple major lineages of orchids: Oncidiinae, Maxillariinae, Zygopetalinae (and a focus on Dichaea), and Sobralieae.  Our current focus is utilizing genome-level data to resolve poorly resolved portions of the phylogenetic tree and to find correlations of diversification with geologic time and life history phenomena unique to these orchids.

Additionally, we are currently developing a DNA dataset for Teagueia, a pleurothallid. is based on the extensive fieldwork and taxonomic expertise of Lou Jost.  In the past decade, he has discovered ~30 new species of Teagueia in a very small region (the Upper Pastaza Valley) of Ecuador.  Preliminary phylogenetic data on this group is showing strong geographic signal, with the strongest biogeographic pattern separating northern and southern groups of species.  Even more remarkable, based on fieldwork, and confirmed by phylogenetic data, the species tend to be mountain/range specific.  Ultrametric analysis has shown that this lineage of Teagueia is very young.

See these phylogenetic papers for further details: Lankesteriana, Botanical Journal of the Linnean Society and Annals of Botany (Oncidiinae), Annals of Botany (Dichaea), American Journal of Botany as well as Katia Silvera’s paper in Functional Plant Biology.

Collaborators: Robert L. Dressler, W. Mark Whitten, Norris Williams, Barbara Carlsward, Lorena Endara, Mario Blanco, Samantha Koehler, Lou Jost, Michael Moore

Funding: American Orchid Society, Vaughn-Jordan Fellowship for orchid biology, start up funds to Neubig at SIU

Polygalaceae

In collaboration with J. Richard Abbott, this project is an effort to better understand the phylogenetics of the family Polygalaceae.  To date, the focus has been on tribe Polygaleae, a widespread group of plants including the genus Polygala.  The biogeographic patterns in the family are remarkable in their worldwide distribution, but especially in their diversification in North America.  Certain groups like the newly circumscribed Rhinotropis represent a radiation in arid western North America and are thus a center of diversity.

As is the case in many very large genera of plants, the genus Polygala is highly polyphyletic.  We are currently working on resolving taxonomic issues related to the polyphyletic Polygala. 

Collaborators: J. Richard Abbott, Barbara Carlsward

Mitreola petiolata

Mitreola petiolata (Loganiaceae) is a widespread annual herb in the southeastern United States, the Caribbean, Latin America, southeast Asia, southern Africa, and northern Australia. Based on inflorescence structure and fruit shape, there are three apparently distinct forms in the New World. The type specimen is from South Carolina and corresponds to the North American form which is also found in the Carib

bean and in Belize, with the other two forms appearing to be sympatric throughout Central America and South America. The relationship between these forms and plants in the Old World is unclear. Does this taxon represent a single widespread polymorphic entity, as currently treated, or might there be three or more cryptic lineages "hiding" within this name?

Data are still being collected, so more to come shortly...

Collaborators: J. Richard Abbott, Ron Liesner

Mikania and the Mikania micrantha complex (Asteraceae)

In a collaborative grant with the USDA, this project aims to help identify and understand the novel invasive species Mikania micrantha in south Florida.  The goals of this project are to help delimit species within this complex (which includes the native M. scandens) and to develop the molecular tools to identify exotic material and the point of origin of exotic material in Florida. Preliminary phylogenetic results show that delimitation in this species complex is very poor.  So, this work is, in part, to help ascertain the monophyletic groups within this complex.  Mikania micrantha is invasive in Asia and, because of it’s aggressive rates of growth, could pose a significant threat to the floristic constituents that are native to southern Florida as well.

Collaborators: J. Richard Abbott, Sharon Talley, Lorena Endara

Funding: USDA*

*Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the funding agency.

Asimina & Deeringothamnus (Annonaceae)

Asimina and Deeringothamnus

are genera in the soursop family (Annonaceae) that are endemic to North America.  In fact, most species are restricted to the southeastern US, especially in Florida. 

In collaboration with Richard Abbott, we have sampled all the species within these two genera for phylogenetic analysis.  We have found that phylogenetic relationships among many species is well resolved.  However, there is some evidence of introgression among species.

Collaborators: J. Richard Abbott

The elm family (Ulmaceae)

Although the elm family is most commonly known for its temperate members, there are also many members in the tropics.  Some previous research has included multiple genera within the family, but these analyses sampled relatively few taxa within the family.  Fortunately, this previous work strongly placed th

e family within order Rosales.  In light of the relatively rich fossil knowledge of elms and their relatives, we are seeking to enrich the phylogenetic sampling of the family.  Using DNA data and fossil information for time calibrations, this project aims to elucidate the relationships of the small elm family.  The phylogeny will also be used to more accurately place fossils within a morphological context. 

This project is ongoing, so more is to come... 

Collaborators: Fabiany Herrera, J. Richard Abbott

Kosteletzkya and tribe Hibisceae (Malvaceae)

Kosteletzkya is genus in the cotton family with over 20 species found in the New World, Africa, Madagascar, and southeast Asia.  Both nuclear and plastid data are being sequenced for most of the species of Kosteletzkya and, in many cases, with multiple accessions per species.  Results from these data show that the aforementioned African and New World species are a monophyletic group.  However, the Malagasy species are very distantly related to the rest.  The other African species form a paraphyletic grade relative to a New World clade.  Recent studies of chromosome counts using pollen mother cells have shown that there exists dipl

oid, tetraploid, and hexaploid species.  Polyploidy has only occurred among some African species, at different times and between different parental constituents.  These data support the relatively ancient formation of an autotetraploid species (K. semota), one recent allotetraploid species (K. borkouana), two relatively ancient, allotetraploid species (K. begoniifolia and K. rotundalata), and one recent allohexaploid species (K. racemosa). 

These preliminary data have revealed an unresolved relationship among two Neotropical species: K. depressa and K. hispidula.  To address the problem of species delimitation for these two very closely related species, undergraduate student Emily Schwartz is using morphological and molecular data.  These data show interesting biogeographic patterns in northwestern Mexico relative to the rest of the New World.

The genus Kosteletzkya represents but a small fraction of the number of species known from the tribe Hibisceae.  The largest genus in this tribe is Hibiscus.  Unfortunately, Hibiscus is highly polyphyletic as noted for many years now, but the phylogenetic sampling in previous studies is relatively scarce, especially for such large genera as Pavonia.  To better understand the relationships, nomenclature and the evolution of chromosome number of the this taxonomically enigmatic tribe, we are boosting the taxom sampling across the tribe.

Collaborators: Orland Blanchard, Jr., J. Richard Abbott, Emily Schwartz, & Stuart McDaniel

North American Astereae (Asteraceae)

Early in the 2000s, Lowell Urbatsch and Roland Roberts developed a preliminary

phylogenetic study of a group of species rich genera in tribe Astereae (especially subtribe Solidagininae).  As a result of the phylogenetic work, it was clear that several large genera (especially Ericameria and Chrysothamnus) were not monophyletic, and so generic nomenclatural changes were necessary.  However, these taxa show extremely low levels of molecular evolution, which makes for poor phylogenetic resolution.  We are currently developing plastome-level datasets for these taxa in order to provide phylogenetic resolution across this difficult group.

Please see our taxonomic papers published in Sida and in Flora of North America.

Collaborators: Lowell Urbatsch

Dichanthelium

Dichanthelium (Poaceae) is a species-rich genus found throughout eastern North America, South America and Hawaii.  However, species-level taxonomy is extremely contentious among plant systematists.  We seek to develop a species-level phylogeny of this group to help resolve the underlying contentious taxonomic issues currently facing floristic studies, especially in the eastern United States.

Collaborators: Lucas Majure, Rob Naczi, J. Richard Abbott, Walter Judd

Neotropical Trema (Cannabaceae)

Trema is a pantropical genus of pioneer trees in the Cannabis family.  Some species are known to hybridize rarely in nature (i.e., T. lamarckiana x T. micrantha and T. cubensis x T. micrantha). Taxonomic issues have also arisen, centered on T. micrantha, due to its polyphyly.

These taxa show extremely low levels of molecular evolution using Sanger data only, which makes for poor phylogenetic resolution.  We are currently developing plastome-level datasets for these taxa in order to provide phylogenetic resolution across this difficult group.

Collaborators: Nancy Garwood