Drivers of community structure and habitat suitability in ponds of the New Caledonia biodiversity hotspot

Coline Royaux , Boris Leroy, Nathalie Mary, Nicolas Charpin, Yvan Le Bras, Nicolas Rabet

Despite being present on all continents including Antarctica, ponds remain an understudied freshwater ecosystem. Ponds are particularly diverse in their physicochemical characteristics which is reflected in the biological assemblages inhabiting them. On the New Caledonia archipelago, acknowledged to be a global biodiversity hotspot, lentic freshwater habitats are numerous. The archipelago is subjected to extremely diverse environmental conditions notably divided along two approximate axes. The north-east has high precipitation rates for the most part (around 3000 mm/y), while the west coast has low precipitation rates (around 900mm/y). On a practically perpendicular axis, the south-east has soils with high heavy metal concentration while it is low in the north-west. We analysed the crustacean species inhabiting small lentic freshwaters and delineated two major assemblages with network clustering analyses. We then modelled the distribution drivers of these communities and identified heavy metal soils and annual precipitation rates as the major drivers. Our models allowed us to project the distribution of suitable areas for each assemblage and suggest the existence of a buffer area between the two assemblages.