"We should be forced to conclude, therefore, that in a large majority of plant genera a clear picture of species interrelationships can never be obtained, were it not for the fact that nature often makes experiments for us."
–––– Stebbins G. L. , Jr. 1950. Variation and Evolution in Plants.
Considering the burgeoning molecular phylogenetic studies in the past two decades have contributed so much to renew our knowledge of the tree of life, it is surprising to realize that we still know so little about plant phylogenetic relationships when close to species level. Stebbins' statement over 50 years ago is still largely true and the major evolutionary questions asked those days remain much the same. Hybridization, introgression, polyploidization, recombination, incomplete lineage sorting, are all potential factors to comfound phylogenetic inferences from molecular data at species or population level.
How to reconstruct a robust species-level phylogeny of a species-rich group that contains a significant part of polyploids and potential hybrids is the central question I am addressing in current research. The Verbena complex are the organisms I am working on.
The Verbena complex includes Verbena, Glandularia, and Junellia, with each genus containing 40 to 50 species. While Junellia (basic chromosome number x=10) is restricted to South America, both Glandularia (x=5) and Verbena (x=7) have a disjunct distribution in South and North America. South American species of Glandularia are predominantly diploid, with their North American counterparts are entirely polyploids, and the reverse is true for Verbena s.s..
Centered on the major question, serveral specific questions for this group are being attacked, and they are classified into 5 categories. Details see the following links.
