<?php
try {
    $sxe = simplexml_load_string($xmlstring, 'SimpleXMLIterator');
    for ($sxe->rewind(); $sxe->valid(); $sxe->next()) {
        if ($sxe->hasChildren()) {
            foreach ($sxe->getChildren() as $element=>$value) {
                echo $value->species . '<br />';
            }
        }
    }
}
catch(Exception $e) {
    echo $e->getMessage();
}