Gaining a (tube) foothold – trends and status following two decades of the long-spined echinoid Diadema setosum (Leske, 1778) invasion to the Mediterranean Sea

The Eastern Mediterranean Sea is an exceptional habitat. Its relative isolation and distinct characteristics create a unique ecosystem recognized as marine biodiversity hot spot, where one-fifth of the species are endemic. Yet, native under increasing threat, mainly due to massive alien invasions Indo-Pacific origin. To date, more than 800 non-indigenous have been reported in Sea, justifying its reputation one most severely affected habitats world terms biological invasions. Here we summarized invasion dynamics long-spined echinoid Diadema setosum (Leske, 1778), ubiquitous sea urchin species. We show alarming exponential population growth D. throughout since 2018, following decade ‘invasion lag’ first detection 2006. Molecular analyses illustrate presence single genetic clade – corresponding Arabian Peninsula this species, reinforcing notion Red Our data support current working hypothesis that initial introduction occurred Northern Levantine Basin from which it gradually expanded both north-west south-east trajectories contrast stepping-stone gradual advancement opening Suez Canal. Demographic along Israeli coastline reveals well-established broad size distributions, juveniles adult individuals remarkably large size. Additionally, provide evidence reproductive capacity new environment. Due magnitude ’s ecological footprint, poses severe threat entire including South Aegean calling for rapid coordinated action at national regional scales.