Otolith morphological divergences of successful Lessepsian fishes on the Mediterranean coastal waters

Here we used a method of morphological niche analysis, previously shown to be an effective predictor of invasion success, to investigate morphological relationships of sagittae otoliths of Lessepsian (Red sea species entering the Mediterranean through the Suez Canal) fishes within the morphospace of the corresponding receiving taxonomic groups. Overall, sagittae of 13 Lessepsian species and 49 closely related native fishes/taxa, distributed in 9 different families or subfamilies were considered, for a total of 305 analyzed otoliths. Based on wavelet functions of 512 Cartesian coordinates, we quantified the degree of morphological disparity produced by the introduction of these species in the hosting community. Lessepsian otoliths tended to be added outside or at the margins of the receiving morphospace, being morphologically divergent from the ones of native species. Considering that many ecological traits of fishes (especially feeding) are mirrored in the shape of otoliths, our findings agree with the idea that these successful invaders may count on novel sensory strategies to compete for available resources and to thrive in newly colonized habitats. Nevertheless, different measurements of morphological disparity did not show any variation before and after invasion and with the specific richness and further investigation is needed to understand to what extent these differentiated sensorial adaptations are linked to novel opportunities along the niche axes, such as in relation to feeding, predatory and anti-predatory behaviour and exploitation of the temporal niche.