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<DIV><A href="http://www3.interscience.wiley.com/journal/117963685/home"><FONT
color=#000000>Journal of Biogeography</FONT></A></DIV>
<DIV><A href="http://www3.interscience.wiley.com/journal/123583813/issue"><FONT
color=#000000>Volume 37 Issue
8</FONT></A>, Pages 1515 - 1528</DIV>
<DIV class=pubOnline>Published Online: 10 Mar 2010</DIV>
<DIV class=title-document xmlns:jencode="java.net.URLEncoder"> </DIV>
<DIV class=title-document xmlns:jencode="java.net.URLEncoder"><FONT size=4>The
relative importance of geography and ecology in species diversification:
evidence from a tropical marine intertidal snail (<SPAN
class=i><EM>Nerita</EM></SPAN>)</FONT></DIV>
<DIV class=author-info xmlns="http://www.w3.org/1999/xhtml"
xmlns:jencode="java.net.URLEncoder"><SPAN class=name><SPAN
class=forenames>Melissa A.</SPAN> <SPAN class=surname>Frey</SPAN><A
href="http://www3.interscience.wiley.com/journal/123318508/abstract#c1"><FONT
color=#000000>*</FONT></A></SPAN> <SPAN class=address>Center for
Population Biology, University of California, Davis, CA 95616, USA </SPAN><A
class=invisible-anchor name=c1> </A><SPAN id=c1> <SPAN
class=number>*</SPAN>Correspondence: Melissa A. Frey, Fisheries and Oceans
Canada, PO Box 6000, Sidney, BC, Canada V8L4B2.E-mail: <A class=externallink
href="mailto:mafrey@ucdavis.edu"><FONT
color=#000000>mafrey@ucdavis.edu</FONT></A></SPAN> </DIV>
<DIV class=bpg40copyright> </DIV>
<DIV class=abstract-title id=h1><STRONG>ABSTRACT</STRONG></DIV>
<DIV class=abstract-content xmlns="http://www.w3.org/1999/xhtml"
xmlns:jencode="java.net.URLEncoder" xmlns:md="urn:mdransfi-functions"
xmlns:f="http://wiley.com/wispers/content/function"
xmlns:xs="http://www.w3.org/2001/XMLSchema">
<P class=para><SPAN class=h5-inline><STRONG>Aim </STRONG></SPAN>In this
study, I examined the relative contributions of geography and ecology to species
diversification within the genus <SPAN class=i><EM>Nerita</EM></SPAN>, a
prominent clade of marine snails that is widely distributed across the tropics
and intertidal habitats. Specifically, I tested whether geographical patterns of
speciation correspond primarily to allopatric or sympatric models, and whether
habitat transitions have played a major role in species diversification.</P>
<P class=para><SPAN
class=h5-inline><STRONG>Location </STRONG></SPAN>Indo-West Pacific, eastern
Pacific, Atlantic, tropical marine intertidal.</P>
<P class=para><SPAN class=h5-inline><STRONG>Methods </STRONG></SPAN>I used
a previously reconstructed molecular phylogeny of <SPAN
class=i><EM>Nerita</EM></SPAN> as a framework to assess the relative importance
of geographical and ecological factors in species diversification. To evaluate
whether recently diverged clades exhibit patterns consistent with allopatric or
sympatric speciation, I mapped the geo-graphical distribution of each species
onto the species-level phylogeny, and examined the relationship between range
overlap and time since divergence using age–range correlation analyses. To
determine the relative contribution of habitat transitions to divergence, I
traced shifts in intertidal substrate affinity and vertical zonation across the
phylogeny using parsimony, and implemented randomization tests to evaluate the
resulting patterns of ecological change.</P>
<P class=para><SPAN class=h5-inline><STRONG>Results </STRONG></SPAN>Within
the majority of <SPAN class=i><EM>Nerita</EM></SPAN> clades examined, age–range
correlation analysis yielded a low intercept and a positive slope, similar to
that expected under allopatric speciation. Approximately 75% of sister species
pairs have maintained allopatric distributions; whereas more distantly related
sister taxa often exhibited complete or nearly complete geographical overlap. In
contrast, only 19% of sister species occupy distinct habitats. For both
substrate and zonation, habitat transitions failed to concentrate towards either
the tips or the root of the phylogeny. Instead, habitat shifts have occurred
throughout the history of <SPAN class=i><EM>Nerita</EM></SPAN>, with a general
transition from the lower and mid-littoral towards the upper and supra-littoral
zones, and multiple independent shifts from hard (rock) to softer substrates
(mangrove, mud and sand).</P>
<P class=para><SPAN class=h5-inline><STRONG>Main
conclusions </STRONG></SPAN>Both geography and ecology appear to have
influenced diversification in <SPAN class=i><EM>Nerita</EM></SPAN>, but to
different extents. Geography seems to play a principal role, with allopatric
speciation driving the majority of <SPAN class=i><EM>Nerita</EM></SPAN>
divergences. Habitat transitions appear insignificant in shaping the early and
recent history of speciation, and promoting successive diversification in <SPAN
class=i><EM>Nerita</EM></SPAN>; however, shifts may have been important for
respective divergences (i.e. those that correspond to the transitions) and
enhancing diversity throughout the clade.</P></DIV></FONT></BODY></HTML>