Phylogenomics in Asarum section Hexastylis: serial innovations in floral form spawned from two geographically-widespread species.
DOI:
https://doi.org/10.55632/pwvas.v90i1.416Keywords:
phylogenomics, pollination, species radiationsAbstract
Asarum section Hexastylis (Aristolochiaceae), is a group of flowering plants endemic to the southeastern United States whose variable floral morphologies and overlapping distributions have long caused taxonomic confusion. Individual species distributions range from the entirety of the southeastern US to only a single gorge. The flowers of section Hexastylis species, to various degrees, appear to have converged on a basidiomycete-like morphology and are putatively pollinated by fungus gnats. Earlier attempts to resolve species boundaries and the evolution of floral traits in the group with commonly-used phylogenetic markers have largely been uninformative at the lowest taxonomic levels.
To uncover species-level relationships, we sequenced thousands of regions dispersed throughout the nuclear genome using Double-Digestion Restriction Enzyme-Associated DNA Sequencing. Data matrices were assembled using the Pyrad pipeline. Phylogenomic inference was conducted under both maximum likelihood and coalescent frameworks. Sequencing was conducted for 97 individuals, representing all taxa in section Hexastylis.
Phylogenomic inference recover two major diversification events within section Hexastylis. Phyletic grades of a geographically-widespread, paraphyletic progenitor species have repeatedly spawned geographically-restricted derivative species with novel floral shapes. Recovered phylogenetic relationships evidence parallel evolution of similar calyx tube shapes, suggesting the operation of geographically partitioned adaptive pressures, most likely associated with fungus gnat pollination.
This work was supported by the National Science Foundation (DEB-1406732) and a William Chambers Coker Fellowship from Highlands Biological Station.
References
Blomquist, H. L. 1957. A Revision of Hexastylis of North America. Brittonia 8(4): 255-281.
Gaddy, L. L. 1987. A Review of the Taxonomy and Biogeography of Hexastylis (Aristolochiaceae). Castanea 52(3): 186-196.
Kelly, L. M. 2001. Taxonomy of Asarum section Asarum (Aristolochiaceae). Systematic Botany 26: 17– 53.
Sinn, B. T., L. M. Kelly, and J. V. Freudenstein. 2015a. Putative floral brood-site mimicry, loss of autonomous selfing, and reduced vegetative growth are significantly correlated with increased diversification in Asarum (Aristolochiaceae). Molecular Phylogenetics and Evolution 89: 194- 204.
Sinn, B. T., L. M. Kelly, and J. V. Freudenstein. 2015b. Phylogenetic relationships in Asarum (Aristolochiaceae): Effect of data partitioning and a revised classification. American Journal of Botany 102(5): 765-779.
Sinn, B. T. 2015c. Asarum chueyi (Aristolochiaceae), a new species from the foothills of the Blue Ridge Mountains of Tennessee and Virginia, USA. Phytotaxa 224(1): 85-95.
Sinn, B. T. 2017. Asarum rosei (Aristolochiaceae), a new species from the Blue Ridge Escarpment of North Carolina, USA. Phytotaxa 296(1): 53-62.
Whittemore, A. T. and L. L. Gaddy. 1997. Hexastylis. In: Flora of North America Editorial Committee, eds. 1993+. Flora of North America North of Mexico. 15+ vols. New York and Oxford. Vol. 3, pp. 54-58.
Yamaji, H., T. Fukuda, J. Yokoyama, J.-H. Pak, C.-Z. Zhou, C.-S. Yang, K. Kondo, T. Morota, S. Takeda, H. Sasaki, and M. Maki. 2007. Reticulate evolution and phylogeography in Asarum sect. Asiasarum (Aristolochiaceae) documented in internal transcribed spacer sequences (ITS) of nuclear ribosomal DNA Molecular Phylogenetics and Evolution 44: 863-884.
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