GeoBio-CenterLMU Bericht 2008/2009 - Ludwig-Maximilians ...

Conventional morphological taxonomy alone clearly is at its limit with the
task of distinguishing closely related but evolutionary distinct sponge line-
ages, especially in character poor taxa. The utilization of additional characters,
such as informative signature DNA sequences (also known as DNA barcodes,
Hebert et al. 2003a, 2003b), and the establishment of a DNA sequence-aided
taxonomic system might provide an opportunity to overcome these short-
comings and aid our future endeavours to strive for more comprehensive
species discoveries and descriptions as well as the deeper understanding
of evolutionary factors that shape species distributions in space and time. In
any case, a DNA sequence-based taxonomic system should by no means re-
place but rather complement conventional taxonomy based on comparative
morphology – the DNA sequences will be regarded as additional characters
to described morphological (and biochemical) features.
Scope
Phylum Porifera (sponges) consists of more than 8,000 described species,
with an estimated species number of 15,000 (Hooper and van Soest 2002).
The Sponge Barcoding Project (SBP) aims at establishing a DNA sequence-
based reference system to aid future species discovery and description. It
will work towards covering species from all sponge taxa, from classes De-
mospongiae, Hexactinellida, and Calcarea, ranging in habitat from the marine
intertidal to the deep-sea, as well as freshwater, and from different biogeo-
graphic regions. In the long term the SBP intends to sequence DNA signature
sequences of about 8,000 taxa. Fresh material of such taxa will be collected
by individual groups involved in the SBP and will be taxonomically identified
by an expert before making DNA signature sequences publicly available via
the project’s website and database.
Background and approach
This is the first worldwide barcoding project on any non-bilaterian taxon, and
intends to cover the complete taxonomic range of Porifera. Several smaller pi-
lot studies have recently been conducted independently, with various levels of
resolution and success (Duran and Rützler 2006, Wörheide 2006). The standard
mtDNA cytochrome oxidase subunit 1 (COI) barcoding fragment, which is used
for almost all current (eukaryotic) barcoding initiatives, spans over a ca. 650
nucleotide region close to the 5’ end (Erpenbeck et al. 2006). This mitochondrial
protein displays sufficient variability in most bilaterian species. However, in non-
bilaterian animals mitochondrial proteins display a lower evolutionary rate (Wör-
heide et al. 2000, Shearer et al. 2002) and it has been shown, that frequently co-
occurring, congeneric sibling sponge species are difficult to separate with COI
fragments (Wörheide 2006) due to very low variability. However, a more variable
Kurzbericht
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