The Royal Society is collaborating with JSTOR to digitize, preserve, and extend access to

Proceedings of the Royal Society of London. Series B, Biological Sciences.www.jstor.org

on February 25, 2013rspb.royalsocietypublishing.orgDownloaded from

on February 25, 2013rspb.royalsocietypublishing.orgDownloaded from

on February 25, 2013rspb.royalsocietypublishing.orgDownloaded from

on February 25, 2013rspb.royalsocietypublishing.orgDownloaded from

on February 25, 2013rspb.royalsocietypublishing.orgDownloaded from

on February 25, 2013rspb.royalsocietypublishing.orgDownloaded from

on February 25, 2013rspb.royalsocietypublishing.orgDownloaded from

on February 25, 2013rspb.royalsocietypublishing.orgDownloaded from

on February 25, 2013rspb.royalsocietypublishing.orgDownloaded from

on February 25, 2013rspb.royalsocietypublishing.orgDownloaded from

on February 25, 2013rspb.royalsocietypublishing.orgDownloaded from

on February 25, 2013rspb.royalsocietypublishing.orgDownloaded from

on February 25, 2013rspb.royalsocietypublishing.orgDownloaded from

on February 25, 2013rspb.royalsocietypublishing.orgDownloaded from

on February 25, 2013rspb.royalsocietypublishing.orgDownloaded from

on February 25, 2013rspb.royalsocietypublishing.orgDownloaded from

on February 25, 2013rspb.royalsocietypublishing.orgDownloaded from

on February 25, 2013rspb.royalsocietypublishing.orgDownloaded from

on February 25, 2013rspb.royalsocietypublishing.orgDownloaded from

on February 25, 2013rspb.royalsocietypublishing.orgDownloaded from