Niche differentiation in Maltese shore crabs (Decapoda: Brachyura)

Abstract

This study investigated the distribution of the littoral rocky shore crabs Pachygrapsus marmoratus, Pachygrapsus maurus and Pachygrapsus transversus, in the Maltese Islands. P. maurus and P. transversus were only recorded from the Maltese islands very recently: P. maurus in 2009 (although subsequently a museum specimen from 1990 was identified) and P. transversus in 2007. Of the 33 rocky shores searched for the crabs, P. marmoratus was found on all the shores, P. maurus was found on 16 shores on the islands of Malta, Gozo and Comino, while P. transversus was only found on three shores on the island of Gozo and Comino. The three Pachygrapsus species were found to co-occur sympatrically only at Dwejra on the western coast of Gozo, which was also the shore where P. maurus was found to be most abundant. The shore at Dwejra is one of the most exposed to wave action in the Maltese islands and this suggests that P. maurus may prefer to live on such high exposure shores, since it was only ' found on the exposed parts of shores and never in embayments.