Sagittal otolith morphology helps to explain the invasion success of Lessepsian species

Abstract

Lessepsian species are marine organisms that enter the Mediterranean from the Red Sea through the Suez Canal. This phenomenon seems to have increased dramatically in recent decades. Here we compared the contour of sagittal otoliths of Lessepsian vs native Mediterranean fishes (families: Atherinidae, Mugilidae, Serranidae, Haemulidae, Callionymidae, Mullidae, Sphyraenidae and subfamilies Clupeinae, Serraninae, Caranginae, Gobiinellinae, Scombrinae). The analyses were based on wavelet functions of an intermediate scale (WLT 5) of 512 cartesian points. A principal components analysis was used to build a morphospace for each group studied. Lessepsian otoliths were characterized by a high morphological differentiation with respect to native ones and tended to be allocated out of the native morphospace. In previous studies we observed that the percentage of correct classifications of Lessepsian otoliths (92.5%) was greater than that obtained by using native species (72%). In some cases (e.g. Plotosidae and Fistularidae), the high morphological distinctness of the Lessepsian otoliths can be attributed to phylogenetic distances between these species and the receiving community. Nevertheless differentiated otolith shapes were also observed in those invaders that are phylogenetically related to native species. This peculiar morphology of Lessepsian otoliths within the Mediterranean context might reflect novel functional and behavioural adaptations of these species and hence novel opportunities to thrive in their newly colonized environment