Systematics and Phylogenetics

Research in my lab has extensively studied the systematics of various groups within Malvaceae. Some particular focal groups have been the following.

The genus Adansonia

David did his dissertation on the pollination biology and systematics of baobabs. Recently, thanks to funding from the NSF and a constructive collaboration with the Wendel/Grover lab at Iowa State University and with UW colleague, Cécile Ané, we have returned to to these charismatic organisms. This work, led by Nisa Karimi, aims to address the following questions:

  1. Is the putative, diploid African baobab species, A. kilima, distinct from the familiar, tetraploid, A. digitata, and is A. kilima actually diploid?
  2. What is the pattern of genetic relatedness across continental Africa? Does it reveal historical patterns of migration?
  3. What are the relationships among the six recognized Malagasy species? Do the four, long-flowered, hawkmoth pollinated species, all of which have yellow/red floral organs, form a clade? Has there been any introgression/hybrid speciation?
  4. What are the relationships among three closely related Malagasy species: A. za, A. madagascariensis and A. perrieri? Are they distinct taxa or a single species complex with clinal variation and/or introgression?
  5. What causes the great variation among individuals African baobab trees in there fruit set? What role does pollinator movement and late-acting self-incompatibility play in explaining this variation.

We are addressing these questions using a diversity of techniques including multilocus phylogenetics using targeted sequence capture and next-gen sequencing, flower cytometry, chromosome counting, pollination observations, and field reproductive biology experiments.

Other groups of Malvaceae we have studied or are studying:

Bombacoideae: Over the years we have published a number of papers on the broad scale phylogeny of Malvaceae, with a special focus on the bombacoid clade. Historically this work was lead by a former post-doc and collaborator, Bil Alverson. Another former post-doc Maria von Balthazar studied floral development in the group.

Malvoideae: Current graduate student Melody Sain, is focusing on North American Malveae, especially the genera Callirhoe and Napaea (with help from undergraduates Abby Schweiner and Jacob Cosby). In the past graduate student Maggie Koopman (now Hanes) studied the phylogeny of Malagasy Malvoideae, with a focus on Hibiscus s.lat. Maggie continues this work in her own lab at Eastern Michigan University.

Byttnerioideae: Former graduate student Barbara Whitlock, now with her own lab at Miami University, studies the phylogeny of the Byttnerioideae clade, which includes the source of chocolate (Theobroma).

Durioneae: Former post-doc Reto Nyffeler, now a curator at the Institut für Systematische und Evolutionäre Botanik in Zurich, studied the phylogeny and evolution of the clade that includes the famous (and famously stink) durian fruit.

Some other plant evolution/systematics projects

Thalictrum (Ranunculaceae). Former post-doc Veronica Di Stilio explored the genetics of sexual dimorphism in dioecious meadowrues. Since then she has done further work on the phylogeny and petal identity in the group as a professor at the University of Washington, Seattle. More recently, my graduate student, Melody Sain, has started using genomic analysis to home in on sex-determining regions in order to see if B-class MADS-box genes might play a role and to evaluate whether the two independent origins of dioecy in the genus utilized similar genetic mechanisms.

Iochroma (Solanaceae). Studied by former graduate student Stacey Smith, who continues to study this group in her own laboratory at the University of Colorado, Boulder.

Scaevola (Goodeniaceae). Studied by former graduate student, Dianella Howarth, who continues to work on Goodeniaceae and related families as a professor at St. John’s University.

Euphorbia (Euphorbiaceae). Studied by former graduate student Ivalú Cacho, now a professor at the Universidad Nacional Autónoma de México (UNAM).