Abstract
Marine organisms that enter the Mediterranean from the Red Sea via the Suez Canal are known as Lessepsian bioinvaders. In general, genetic studies of Lessepsian fishes have shown little structure between Red Sea and Mediterranean populations. Yet notable exceptions suggest the importance of life-history factors that may influence patterns of spatial genetic variation. In this study, by sampling two invasive fishes with different life histories (the rabbitfish Siganus rivulatus and the filefish Stephanolepis diaspros), we looked at evidence of population structure and selection at the boundary between the Red Sea and the Mediterranean (the Suez Canal), using thousands of molecular markers. Results illustrate two divergent patterns of genetic patterns, with little genetic structure in S. rivulatus and strong population structure in S. diaspros, even at such small spatial scale. We discuss differences in ecological characteristics between the two species to account for such differences. In addition, we report that in the face of both high (S. rivulatus) and low (S. diaspros) gene flow, loci under selection were uncovered, and some protein coding genes were identified as being involved with osmoregulation, which seems to be an important feature of individuals crossing the salinity-variable Suez Canal. The presence of genes under selection in populations near the Suez Canal supports the idea that selection may be active and essential for successful invasions right out of the gate.
Highlights
Over the last decades, molecular techniques have provided important innovation in the field of invasion biology (Rius et al 2015), especially in the last few years with the use of genomic approaches (Bernardi et al 2016; Barbosa 2021; Stuart et al 2021)
We focused our attention on the spatial component of the question, by looking at the region closest to the Suez Canal, in order to determine if any evidence of population structure or selection was present at the boundary between the Red Sea and the Mediterranean
Genomic DNA was sequenced from a total of 78 samples (38 Siganus rivulatus and 40 Stephanolepis diaspros) in an Illumina lane producing approximately 100 million reads
Summary
Molecular techniques have provided important innovation in the field of invasion biology (Rius et al 2015), especially in the last few years with the use of genomic approaches (Bernardi et al 2016; Barbosa 2021; Stuart et al 2021). Founding effects should be revealed by a decrease in genetic diversity resulting from bottlenecked populations. Despite their lowered evolutionary potential, and due to a combination of ecological and biological characteristics, these species can still become successful in their new environment Azzurro et al 2006; Xue et al 2018) This is known, in invasion biology, as the ‘genetic paradox’ (Roman and Darling 2007)
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