Daphnia diversity in water bodies of the Po River Basin

<p>Shallow water bodies dominate the areal extent of continental waters and host a proportion of biodiversity higher than the percentage of Earth’s surface they cover. <em>Daphnia</em> is a key component of small aquatic ecosystems food webs. Here we present the result of a survey in 24 ponds located in the core of Po river Basin, to assess the actual spreading of <em>Daphnia</em> species in one of the most productive areas of the Northern hemisphere. By using diagnostic genetic markers (<em>12S rRNA </em>and <em>ND5 </em>genes) we identified five <em>Daphnia</em> species: <em>D. ambigua</em>, <em>D. curvirostris</em>, <em>D. longispina</em>, <em>D. obtusa</em> and <em>D. pulex </em>in fourteen ponds. Additional analyses of two nuclear genes (<em>LdhA</em> and <em>Rab4</em>) revealed that <em>D. pulex</em> in the study area is native European strain. In opposite, <em>D. ambigua</em> shared haplotype with the North-Eastern American lineage that was introduced to Europe by long-distance dispersal. In the Po river Basin we identified a highly divergent lineage of <em>D. longispina </em>group that formed a clade with individuals from northern European Russia and might represent a new <em>Daphnia </em>species. <em>Daphnia</em> species in the Cremona province have European origin, except for <em>D. ambigua</em> which is a North American species spreading across Europe. Future attention will require monitoring of invasive species, particularly <em>D. ambigua</em> and the North American invasive clone of <em>D. pulex </em>that is already present in Northern Italy. </p>