Case Study
Submitted By
| Name: | Benjamin van Ee |
| Institution: | University of Wisconsin-Madison |
| Country: | USA |
| Email: | bvanee@wisc.edu |
Title & Categories
| Case Study Title: | Identification of Croton (Euphorbiaceae) specimens from Panama to Canada using DNA barcoding |
| Focus Theme: | Adding barcodes to a large survey of a taxonomic group |
| Geographic Region: | North America |
| Habitat Type: | Terrestrial - Other |
| Taxonomic Group: | c: PLANTS |
Scope
Croton (Euphorbiaceae s.s.), with over 1,200 species, is one of the largest genera of flowering plants. This study aims to use the nuclear ribosomal ITS and 5.8S DNA regions to barcode the members of Croton found on the mainland of Central and North America. With just less than 200 species represented, this area is considered one of the hotspots of Croton diversity. Although numerous new collections of Croton have been made specifically for this study, the vast majority of accessions are already curated herbarium collections. Given the sheer size of Croton, this study focuses on those taxa from a given geographic area, thereby reducing the sample size to a manageable number while maintaining a meaningful sampling for the purpose of specimen identification. The project is near completion, having begun as a portion of Ben van Ee’s graduate research work in 2002, and is being done in the context of a broader systematic and taxonomic revision of the genus.
Purpose
This study aims to create a DNA barcode database useful for identifying specimens of Croton from Panama to Canada (mainland only) to species, or at least to section. Less than half of the approximately 1,200 species of Croton have been assigned to one of the 40 sections described by Grady Webster in 1993. Of the approximately 190 species of Croton in the geographic region of this study, about one third are unassigned to section, and many have been placed in different sections by different authors. In many herbaria there are numerous misidentified and unidentified collections of Croton. This project will result in all of the species from the geographic region being assigned to a section, as well as an estimate of inter- and intraspecific variation so that any collection from the region that is sequenced for ITS can be identified to species, or to a very small group of species, with a quantified estimate of certainty.
Background
The first molecular phylogenetic study of Croton was published in 2005, since then several hundred more taxa have been sequenced for ITS and other DNA regions. There is currently a large amount of molecular genetic information available on Croton and this study is one way of putting that vast amount of information to work.