National Science Foundation, DEB 0343735: Phylogenetic relationships and character evolution in tribe Lycieae (Solanaceae)

This National Science Foundation funded project (with co-PI Dr. Rachel A. Levin) examined evolutionary relationships among three closely-related genera (Grabowskia, Lycium, Phrodus) in tribe Lycieae in the tomato family (Solanaceae).  We traveled widely with students to document distributions and collect members in this group. 

Our work has resulted in revised taxonomic classifications (Levin et al. in press) and provided a new systematic treatment for the tribe.  In addition, this work has explored variation in sexual systems (i.e., separate male and female plants versus hermaphroditism) and tested working hypotheses concerning the association of polyploidy, loss of self-incompatibility, and gender dimorphism. 

More broadly, this project has advanced our understanding of angiosperm phylogeny, as well as contributed to on-going, global efforts toward deciphering relationships in the economically important plant family Solanaceae.

National Science Foundation, DEB 0843364: Fine scale phylogenetic relationships in Lycieae (Solanaceae): a multilocus approach for understanding biogeography, polyploidy, and reproductive evolution

The field of phylogenetic systematics has been transformed recently by the use of multilocus and genomic data, and this National Science Foundation funded project (with co-PI Dr. Rachel A. Levin) will continue to develop genomic resources and test newly developed methods for phylogenetic inference. The plant genus Lycium has emerged as an excellent model system for understanding the evolution of hybridization, polyploidy and reproductive strategies, and a robust understanding of relationships will facilitate the study of these characteristics. 

We will take a novel approach, combining traditional phylogenetics with molecular population genetic techniques, to infer changes in populations over evolutionary timescales (e.g., historical population sizes, dispersal patterns, relationships among populations within species).

Previous data from the lab suggests that hybrid species formation may be relatively common in Lycium; thus, an important goal of this project is to assess the importance of hybridization and its consequences for speciation.  Molecular evidence will be used to untangle the evolutionary histories of several putatively hybrid species.

In addition, an exceptional species has been described with polymorphism across populations for both sexual system and ploidy level (Yeung, Miller et al. 2005).  That is, some populations are hermaphroditic, whereas others have separate sexes.  Remarkably, the association between gender and polyploidy described previously (Miller & Venable 2000) is also present within this species (i.e., hermaphroditic populations are diploid, whereas dimorphic populations are polyploid).  Species with population level variation in sexual systems provide excellent opportunities to isolate selective factors contributing to evolutionary transitions.