Cytogeography of Callisia section Cuthbertia (Commelinaceae).

Iwan E Molgo,Douglas E Soltis,Pamela S Soltis

doi:10.3897/compcytogen.v11i4.11984

Abstract

Determining the distribution of cytotypes across the geographic distribution of polyploid complexes can provide valuable information about the evolution of biodiversity. Here, the phytogeography of cytotypes in section Cuthbertia (Small, 1903) Hunt, 1986 is investigated. A total of 436 voucher specimens was georeferenced; 133 new specimens were collected. Based on flow cytometry data, DNA content of all cytotypes in section Cuthbertia was estimated. Utilizing chromosome counts and flow cytometric analysis, cytotype distribution maps were generated. Two disjunct groups of populations of diploid Callisia graminea (Small, 1903) Tucker, 1989 were discovered; tetraploid C. graminea ranges broadly from the coastal plain of North Carolina through central Florida. One hexaploid C. graminea individual was recorded in South Carolina, and numerous individuals of hexaploid C. graminea were found in central Florida. Diploid C. ornata (Small, 1933) Tucker, 1989 occurs in eastern Florida; previously unknown tetraploid and hexaploid populations of C. ornata were discovered in western and central Florida, respectively. Diploid C. rosea (Ventenat, 1800) Hunt, 1986 occurs in Georgia and the Carolinas, with populations occurring on both sides of the Fall Line. The cytotype and species distributions in Callisia are complex, and these results provide hypotheses, to be tested with morphological and molecular data, about the origins of the polyploid cytotypes.

Highlights

Polyploidy is a speciation mechanism that is a major evolutionary force; all angiosperms have undergone at least one ancient polyploidy event (Jiao et al 2011, Amborella Genome Project 2013), and polyploidy has been a key driver of angiosperm diversity (De Bodt et al 2005, Soltis et al 2009, Soltis and Soltis 2009, Soltis and Soltis 2016, Tank et al 2015).Polyploids are classified in two major categories: allopolyploids and autopolyploids
Georeferencing – Callisia section Cuthbertia consists of three species native to the southeastern U.S.A., with three ploidal levels within C. graminea and C. ornata and diploids in C. rosea
The map of the geographic distribution (Figure 1) of all georeferenced voucher specimens depicts all specimens of C. graminea, C. ornata, and C. rosea without ploidal levels, collected from 1894 until present

Summary

Introduction

Polyploidy (whole-genome duplication) is a speciation mechanism that is a major evolutionary force; all angiosperms have undergone at least one ancient polyploidy event (Jiao et al 2011, Amborella Genome Project 2013), and polyploidy has been a key driver of angiosperm diversity (De Bodt et al 2005, Soltis et al 2009, Soltis and Soltis 2009, Soltis and Soltis 2016, Tank et al 2015). Polyploids are classified in two major categories: allopolyploids and autopolyploids. Allopolyploids are by far the more studied form and arise via hybridization between species, whereas autopolyploids originate from the multiplication of genomes within a single species. Lumping diploid progenitors with their multiple derivative cytotypes into a single species may mask evolutionary lineages and grossly underestimate biodiversity (Soltis et al 2007)

Methods

Results

Conclusion