This issue presents studies on alien species from Asia, Europe, North and Central America!

 In this issue…

 The orange sponge Hymeniacidon sinapium has colonized estuaries and intertidal areas in Asia, Europe, South America, and Africa, being the most widely distributed alien sponge known up to now!

 Rapid growth of giant salvinia Salvinia molesta impeded access to and decreased the water quality in an urban lake of Puerto Rico. Management actions are necessary!

 The alligator weed Alternanthera philoxeroides can cope well in disturbed and undisturbed habitats, thus colonizing a variety of environments.

 Twenty-nine alien freshwater macroinvertebrates are reported for Croatia, and most come from the Ponto-Caspian area.

 Analyses of morphological and genetic characteristics revealed the presence of the Asian freshwater snail Sinotaia cf. quadrata in Spain and France.

 Environmental factors influence the external shell color of the Asian clam Corbicula fluminea while genetics is responsible for the internal shell color.

 More than 200 alien fish introduced to Malaysia for food, ornamental, recreational and biological reasons have economic gains but also cause ecological impacts.

 Possible competition between the European flounder Platichthys flesus, alien to Iceland, and the native European plaice Pleuronectes platessa due to a similar diet and occupation of same areas.

 Another round goby Neogobius melanostomus in the wall! How this fish can use and occupy vertical structures in Switzerland.

 Please visit our website and download Volume 15 Issue 4 of Aquatic Invasions – it's Open Access!