Case Study
Title & Categories
| Case Study Title: | Clarification of species of Didemnum (Ascidiacea, Tunicata) from 3 continents through DNA barcoding |
| Focus Theme: | Experimental application of barcodes to a new taxonomic group |
| Geographic Region: | Oceania, North America, Europe |
| Habitat Type: | Marine nearshore benthos |
| Taxonomic Group: | e: Tunicata |
Scope
Material In house: 5 specimens each from 1)Rhode Island, 2)San Francisco, California (x 8 sites).
Material to be collected: from 3)Netherlands and 4)France via Francis Kerkhoff, 8)Avery Point, Connecticut via Rick Osman 10) New Zealand (Genbank 18S rRNA only) possibly via Chad Hewitt or Ashley Coutts.
For Comparison: 1)Didemnum carnulentum San Francisco, CA.
Total samples, if all areas collected (5 specimens each) = 70 specimens x 12.70 = $889.
Costs based on estimates from Table 1, “Protocols for High-Volume DNA Barcode Analysis”.
Purpose
To clarify the taxonomic relationships of several species of Didemnum including, Didemnum vexillum Kott, 2002 (New Zealand), D. lahillei Hartmeyer, 1909 (Europe), D .vestum Kott, 2004 (east coast US), Didemnum sp. (west coast US) with the ultimate goal of determining how many of these are valid species and where they’ve originated.
Background
Didemnum sp (Kott, 2004 identified specimens from New Hampshire as a new species, D. vestum) currently ranges from Cobscook Bay, Maine to Long Island Sound on the east coast of the US, and from Southwestern British Columbia to Elkhorn Slough, California on the west coast. The same or a very similar species was identified recently in New Zealand, at multiple localities, D. vexillum. Yet another morph of this or a closely related species, Didemnum lahillei was described in the Mediterranean in 1909. Currently no molecular data exists to settle whether these are in fact, separate species and whether any of them are invasive (Kott, 2004). On the east coast of the US this Didemnum sp is a newly recorded species in many areas, spreading rapidly, creating monoclonal matts and reeking havoc on ecosystems (Science News online, 2005: USGS Monthly Newsletter, 2005). It has the potential to change the nature of bottom communities in large areas off the North east coast of the United States, as well as other parts of the world.
Logistics
Many studies of tunicates are at the phylogenetic level, using 18S sequences (Stach, 2002). There are few species level studies of tunicates using COI despite the fact that COI DNA sequence data can be used quite successfully to resolve taxonomic issues (Castilla et al., 2002). We hope CBOL will take this on as a pilot project which we can expand and use as a basis for a more comprehensive molecular study of fouling marine invertebrates. Our settlement plate studies in coastal systems are ongoing. In house specimens are available immediately for prep and workup. SERC is prepared to do the prep work as necessary.