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<DIV class="citation articleInformationHeader"
xmlns="http://www.w3.org/1999/xhtml"><STRONG>Journal of Ecology</STRONG></DIV>
<DIV class=articleDetails><A
href="http://onlinelibrary.wiley.com/doi/10.1111/jec.2011.99.issue-3/issuetoc"
shape=rect><FONT color=#000000><SPAN id=volumeNumber>Volume 99</SPAN>, <SPAN
id=issueNumber>Issue 3</SPAN>, </FONT></A><SPAN id=issuePages>pages
807–817</SPAN>, <SPAN id=issueDate>May 2011</SPAN></DIV>
<DIV>Article first published online: 23 FEB 2011</DIV>
<DIV id=doi>DOI: 10.1111/j.1365-2745.2011.01800.x</DIV></DIV>
<DIV class=articleTitle> </DIV>
<DIV class=articleTitle><FONT size=4>Predation risk indirectly enhances survival
of seaweed recruits but not intraspecific competition in an intermediate
herbivore species</FONT></DIV>
<DIV class="citation articleInformationHeader" id=cr1
xmlns="http://www.w3.org/1999/xhtml">Markus Molis<SUP>1,*</SUP>, Inken
Preuss<SUP>2,<A
href="http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2745.2011.01800.x/abstract#fn1"
shape=rect><FONT color=#007e8a>†</FONT></A></SUP>, Annika Firmenich<SUP>3</SUP>,
Julius Ellrich<SUP>4,<A
href="http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2745.2011.01800.x/abstract#fn2"
shape=rect><FONT color=#007e8a>‡</FONT></A></SUP></DIV>
<DIV class="citation articleInformationHeader"
xmlns="http://www.w3.org/1999/xhtml"><SUP>1</SUP> Section Functional Ecology,
Biologische Anstalt Helgoland, Alfred-Wegener-Institute for Polar and Marine
Research, marine station, Kurpromenade 201, D-27498 Helgoland,
Germany<SUP>2</SUP> Department of Sustainable Sciences, Leuphana University of
Lüneburg, Scharnhorststraße 1, D-21335 Lüneburg, Germany<SUP>3</SUP> Marine
Biology Department, University of St Andrews, Scottish Oceans Institute, East
Sands, St Andrews KY16 8LB, Scotland, UK<SUP>4</SUP> Department of Morphology
and Evolution of Animals, Philipps University, Karl-von-Frisch-Straße 8, D-35043
Marburg, Germany. Correspondence: Markus Molis, E-mail: <!--TODO: clickthrough URL--><A title="Link to email address"
href="mailto:markus.molis@awi.de" shape=rect><FONT
color=#007e8a>markus.molis@awi.de</FONT></A></DIV>
<DIV class="citation articleInformationHeader" id=additionalInformation
xmlns="http://www.w3.org/1999/xhtml">
<DIV style="CLEAR: left">
<DIV jQuery1302975982236="8"><SPAN class=bullet><SUP><FONT
size=1>†</FONT></SUP></SPAN> Present addresses: Institute of Soil Science,
University of Hamburg, Allende-Platz 2, D-20146 Hamburg, Germany.</DIV>
<DIV jQuery1302975982236="8"><SPAN class=bullet><SUP><FONT
size=1>‡</FONT></SUP></SPAN> Marine Ecology Lab, Saint Francis Xavier
University, Antigonish, B2G 2W5, Nova Scotia, Canada.</DIV>
<DIV id=publicationHistoryDetails jQuery1302975982236="10">
<H4>Summary</H4></DIV></DIV></DIV>
<DIV id=productContent>
<DIV id=fulltext xmlns="http://www.w3.org/1999/xhtml">
<DIV id=abstract>
<DIV class=para>
<P><B>1.</B> Non-consumptive predator effects are an important driver in
predator–prey interactions. While indirect effects of predation risk shape
interspecific species interactions, e.g. in fuelling trophic cascades, knowledge
about non-consumptive predator effects on intraspecific interactions among
intimidated prey is scarce.</P></DIV>
<DIV class=para>
<P><B>2.</B> In laboratory experiments, we tested whether predation by male and
female green crabs (<EM>Carcinus maenas</EM>) is stronger on small than on
larger specimens of the periwinkle <EM>Littorina littorea</EM>, an important
herbivore species in intertidal habitats of the temperate zone. Moreover, we
asked whether size-specific differences in predation-induced mortality reflect
as a stronger effect of predation risk (caused by nearby consuming crabs) on the
foraging behaviour of more threatened periwinkles and ultimately on the
recruitment success of the brown seaweed <EM>Fucus serratus</EM>. Furthermore,
predator activity and prey abundance was measured in the field and the efficacy
of predation risk on the survival of seaweed recruits was assessed in three
field experiments with two different set-ups (open plots and crab
exclosures).</P></DIV>
<DIV class=para>
<P><B>3.</B> Male crabs consumed smaller periwinkles more often than larger
conspecifics, while females refused periwinkles as food. In summer, 80–90% of
periwinkles in the field attained a size at which crab predation was minimal in
laboratory assays. The observed up to 15-fold decrease in the consumption of
seaweed recruits by periwinkles in the presence of nearby consuming crabs in
laboratory assays was, however, independent of the size of periwinkles.
Predation risk effects from the laboratory were only confirmed in field
experiments using crab exclosures but not with open plots, suggesting an
artefact due to trespassing by wild crabs in the open plot set-up.</P></DIV>
<DIV class=para>
<P><B>4.</B> <EM>Synthesis</EM>. Predation risk may not change intraspecific
competition for food in <EM>L</EM>. <EM>littorea</EM>. Yet, risk effects on
foraging behaviour of periwinkles that experience a low threat of real predation
indicate that non-consumptive predator effects may affect prey population
dynamics more strongly than consumptive predator effects. Thus predation risk
effects may be indirectly beneficial for the survival of basal species like
perennial seaweeds, as experimental evidence from field and laboratory
experiments indicates.</P></DIV></DIV></DIV></DIV></FONT></BODY></HTML>