Biology Reference
In-Depth Information
naturally (the latter may have occurred in timescales of hundreds to thousands of years
before present). However, a molecular phylogeographic approach may represent a
sufficiently robust strategy to delineate the cryptic taxa and, most importantly, provide
information on the origins of the invader and the direction of the invasion process (see
Box 12.1 ; Voisin et al. 2005 ; Andreakis et al. 2007a , b ;Sherwood 2008 ).
When cryptic taxa remain unrecognized, significant evolutionary and ecological
changes of the local marine biodiversity at the subspecies level will remain unknown.
Most importantly, cryptic invasions generally escape the critical management
mechanisms of early detection, control, and future prevention. Conversely, if cryptic
taxa are misidentified, the impacts of invasions can be erroneously overestimated due
to the co-occurrence of morphologically similar invasive and noninvasive cryptic
ESUs belonging to the same species-complex.
The increased recognition of cryptic ESUs has significantly changed our view of
distribution, abundance, ecophysiology, and conservation status of seaweed spe-
cies. In the light of the high rate with which new ESUs are discovered, firstly, the
taxonomic status of several so-called cosmopolitan species has to be reconsidered.
Secondly, the newly emerging patterns can be used to formulate hypotheses on
diversification rates and to discover biodiversity hotspots. Thirdly, and most impor-
tantly, results are essential to develop accurate assumptions on extinction risks and
population sizes. Marine science in the post-genomic period with hundreds of
genomes sequenced so far requires a convincing yet suitable taxonomic unit. This
is of crucial importance to corroborate ecological, biological, and evolutionary
interpretations, but also for practical applications such as management of Marine
Protected Areas and active bio-invasion control programs.
12.4 Are Introduced Species a Pest or Prize? A Crab's Tale
The Chinese mitten crab is native to the rivers and estuaries of the Yellow Sea in
Korea and China, and has been introduced to many regions of the world. The two
quotations below illustrate the conundrum whether this crab species is a pest or a
prize. Counting the number of scientific publications on this species (ISI web of
Knowledge, viewed 05 April 2011) suggests the latter, as most publications report
on aspects of economic use, e.g.,
reproductive performance and breeding
optimization.
The Chinese mitten crab ( Eriocheir sinensis ) is considered one of the world's
top 100 invaders by the Invasive Species Specialist Group (ISSG), part of the
Species Survival Commission of The World Conservation Union (IUCN).
Populations of E. sinensis have recently become established on the west coast of
the U.S. and now pose a potential threat to the native fishes and invertebrates and to
freshwater and brackish estuarine communities ” (Dittel and Epifanio 2009 ).
The Chinese mitten crab (Eriocheir sinensis) is one of the most important
cultivated aquatic species in northern China. Significant advances have been
made in the crab farming during last years due to its “high market value with
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