Abstract
The present work reports on the presence and distribution of an alien and invasive gastropod, Ferrissia fragilis (Tryon, 1863), in freshwater systems of the oceanic islands of the Azores archipelago. First registered in 2007, F. fragilis was found in S. Miguel, Santa Maria, and Graciosa. This study increases to 6 the number of freshwater species of mollusks occurring in the Azores. Remarks are added on the possible impact of invasive species in island freshwater systems.
Highlights
The geographic position of oceanic islands strongly limits dispersal and colonization of freshwater systems, resulting in a “disharmonic” fauna, characterized by low levels of diversity and high abundance of insect orders when compared to continental systems
The record of Ferrissia fragilis in the Azores corresponds to the only register of the species in the oceanic islands of Macaronesian region
The record of F. fragilis increases to 6 the number of species occurring in the archipelago, distributed across 2 classes and 4 families (Table I)
Summary
The geographic position of oceanic islands strongly limits dispersal and colonization of freshwater systems, resulting in a “disharmonic” fauna, characterized by low levels of diversity and high abundance of insect orders when compared to continental systems. Oceanic islands are potentially highly vulnerable to invasive species due to the low levels of diversity (and competitors) and the resulting availability of ecological niches (Covich 2009). Freshwater biotas and ecosystems are being profoundly reshaped by ongoing human mediated transoceanic biotic exchange (Benson 1999). Members of the ancylid gastropod genus Ferrissia Walker, 1903 are found worldwide in freshwater ecosystems but have received relatively little systematic attention in recent decades. Ferrissia freshwater limpets have been identified from several European and Asian countries under different names: Pettancylus petterdi (Johnston, 1879), P. australicus (Tate, 1880), Ferrissia wautieri (Mirolli, 1960), Ferrissia clessiniana (Jickelli, 1882) (Raposeiro et al 2007; Son 2007). Walther et al (2006), Walther (2008) and (Walther et al 2010)
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