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

The Sponge Barcoding Project
Gert Wörheide and Dirk Erpenbeck, Department für Geo- und
Umweltwissenschaften, Paläontologie & Geobiologie, LMU München
Sponges are among the most ancestral metazoans (e.g., Philippe et al. 2009)
and may hold many clues to our understanding of the evolution of early ani-
mal and developmental processes (Srivastava et al. 2010). They are highly
diverse, abundant in nearly every aquatic habitat, some freshwater and most
marine, and play numerous important ecological roles, e.g. in nutrient cycling
(Lesser 2006) or as bioeroding organisms in coral reefs (Lopez-Victoria and
Zea 2005). Their significant commercial importance to the pharmaceutical
and biomaterials industry is increasingly being recognized, e.g. as producers
of highly potent secondary metabolites (reviewed in e.g. Faulkner 2000) useful
for drug development (Munro et al. 1994).
Many sponge species are notoriously difficult to identify, often even by
taxonomic experts, because morphological characters for comparative
morphology are scarce and prone to homoplasies, highly variable or other-
wise unsuitable for unambiguous identification. In addition, many sponges
discovered in large scale biodiversity surveys remain undescribed (Hoo-
per and Ekins 2005), partly also due to the lack of skilled taxonomists.
As a result of uncertainties in morphological systematics, sponge species
have frequently been regarded as widely distributed (‘cosmopolitan’). Ho-
wever, genetic approaches, mostly using allozymes, have clearly shown
that such cosmopolitan sponge species are rare and appear to result from
over-conservative systematics, lumping morphologically similar but evolu-
tionary distinct lineages into one widely distributed morpho-species (e.g.
Klautau et al. 1999). The question of how to describe and distinguish such
genetically distinct and reproductively isolated lineages remains complica-
ted, due to the difficulty of relating those genetic differences to morpho-
logical delineation of ‘species’. Secondly, however, what is a species in
sponges?
While the use of fixed differences in “diagnostic” morphological characters
(e.g. spicules and architecture) is practical and has served reasonably well to
catalogue diversity, it is doubtful that such a typological system reflects the
real biological diversity. Sponge alpha-taxonomy still is a quite artificial sy-
stem solely based on morphological differences without considering evoluti-
onary history and/or reproductive isolation. Nonetheless, correctly identifying
reproductively isolated and evolutionary distinct lineages of sponges remains
pertinent for understanding a broad range of subjects such as marine ecolo-
gy, biodiversity, dispersal, animal evolution and discovery of pharmaceutically
/ biotechnologically valuable taxa.
Kurzbericht
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