I'm interested in investigating multiple elements of diversification (molecular divergence, morphological disparity, macroevolution) using species-level phylogenetics—a "process" approach. I'm also interested in integrating a broad spectrum of data (ecological, phylogenetic, cytological, morphological, etc.) into a cohesive taxonomic understanding of a group—the "pattern" approach.
Within the pattern/process framework outlined above, I’m seeking to develop an empirical dataset to evaluate the long-term evolutionary potential of polyploids (taxa with more than the typical two complete sets of chromosomes). Polyploidy is a common, widespread phenomenon, especially in plants, and there is an extensive literature on both the prevalence of new polyploids (polyploid formation) and on the existence of polyploid ancestors deep in the tree of life. The new polyploids demonstrate that this seemingly unlikely mutation (doubling of chromosome sets) occurs relatively frequently; the ancient polyploid ancestors (paleopolyploids) show that polyploid lineages can, at least occasionally, diversify into large clades (including the vertebrates, and the angiosperms).
What we are lacking, however, is an understanding of the general evolutionary fate of polyploid taxa. Do they tend to go extinct quickly (and are thus “evolutionary noise”) or do they comprise potent material for future diversification and the generation of evolutionary novelty? Given the prevalence of extant polyploids today, this question has profound implications for our understanding of planetary biodiversity.
This question is additionally interesting/fun/intimidating because it resides at the intersection of a number of phylogenetic challenges. Most polyploids involve reticulate patterns of evolution, and thus their history cannot be fully represented by the classic bifurcating evolutionary tree. And chromosome number evolves according to mathematical relationships not incorporated in classic ancestral character state reconstruction methods. And the state of being polyploid may influence a lineage’s propensity to diversify, and thus the character state reconstructions and “tree” inference need to be performed simultaneously. And so on.
I'm whittling away at these issues using low-copy nuclear sequence data from the fern genus Cystopteris, a genus of some 20 – 30 species, is a legendary taxonomic and evolutionary bugbear (at least within fern circles), blessed with rampant polyploidy. Much of the confusion surrounds a single named taxon—Cystopteris fragilis—that, as typically circumscribed, occurs on every continent save Antarctica, and at ploidy levels ranging from diploid (two chromosome sets) to octaploid (eight sets).
My eternal gratitude, then, to any hardy souls who are willing and able to send me Cystopteris (or Gymnocarpium, or Acystopteris, or Cystoathyrium) specimens from across their range. If you might be in this category, please let me know and we can negotiate (and I can describe the sorts of material that are particularly helpful.)