Evidence of niche conservatism and host fidelity in the polar shrimp Lebbeus kiae n. sp. (Decapoda: Caridea: Thoridae) from the Ross Sea, Antarctica

We report a remarkable case of ‘bipolarism’, where two different polar species, namely Lebbeus polaris in the northern hemisphere and Lebbeus kiae n. sp., here described from the Southern Ocean, have been found to share similar ecologies. Despite the great geographical distance between the two species, both show high host fidelity in associations with two congeneric sea anemones: Bolocera tuediae and Bolocera kerguelensis, respectively. A close molecular phylogenetic relationship between the two Lebbeus species is indicated by COI data, which clearly show them as sister clades with respect to other congeners as well as a plurality of other Antarctic species. This is the first reported case of a defensive association in the Southern Ocean involving shrimps and sea anemones. The distribution of the new species, limited to seamount systems off the Ross Sea, may be the result of a specific colonisation/speciation event in the past, although more molecular data are needed to unravel the phylogenetic relationships within the genus Lebbeus. Despite this uncertainty, the persistence of ecological traits, i.e., the defensive association with sea anemones, indicates the presence of niche conservatism in this clade of shrimps.