Two centuries for an almost complete community turnover from native to non-native species in a riverine ecosystem.

Non-native species introductions affect freshwater communities by changing community compositions, functional roles, trait occurrences and ecological niche spaces. Reconstructing such changes over long periods is difficult due to limited data availability. We collected information spanning 215 years on fish and selected macroinvertebrate groups (Mollusca and Crustacea) in the inner-Florentine stretch of the Arno River (Italy) and associated water grid, to investigate temporal changes. We identified an almost complete turnover from native to non-native fish (1800: 92% native; 2015: 94% non-native species) and macroinvertebrate species (1800: 100% native; 2015: 70% non-native species). Non-native fish species were observed ~50 years earlier compared to macroinvertebrate species, indicating phased invasion processes. In contrast, α-diversity of both communities increased significantly following a linear pattern. Separate analyses of changes in α-diversities for native and non-native species of both fish and macroinvertebrates were nonlinear. Functional richness and divergence of fish and macroinvertebrate communities decreased non-significantly, as the loss of native species was compensated by non-native species. Introductions of non-native fish and macroinvertebrate species occurred outside the niche space of native species. Native and non-native fish species exhibited greater overlap in niche space over time (62%-68%) and non-native species eventually replaced native species. Native and non-native macroinvertebrate niches overlapped to a lesser extent (15%-30%), with non-natives occupying mostly unoccupied niche space. These temporal changes in niche spaces of both biotic groups are a direct response to the observed changes in α-diversity and species turnover. These changes are potentially driven by deteriorations in hydromorphology as indicated by alterations in trait modalities. Additionally, we identified that angling played a considerable role for fish introductions. Our results support previous findings that the community turnover from native to non-native species can be facilitated by, for example, deteriorating environmental conditions and that variations in communities are multifaceted requiring more indicators than single metrics.

A range extension of a deep-sea barnacle of the genus Aurivillialepas (Cirripedia, Scalpellomorpha), a Macaronesian and amphitropical refugial genus having Mesozoic affinities.

The scalpellomorph barnacle, Aurivillialepas calycula (Aurivillius, 1898), previously known only from Macaronesia, is reported from Banco de Galicia, off the NW corner of the Iberian Peninsula. One of the two specimens was attached to the scleractinian coral, Madrepora oculata Linnaeus, 1758. Since such pedunculate barnacles are little known, the potentially hermaphroditic specimens and its complemental male are illustrated photographically, and a key to the genus Aurivillialepas is provided. The genus, together with Scillaelepas Seguenza, 1876 and Gruvelialepas Newman, 1980, has long been considered to constitute a natural group of scalpellomorphs within the Calanticidae, and therefore the Scillaelepadinae subfam. nov. is proposed to accommodate them. Biogeographical aspects of these deep-sea barnacles support the hypothesis that not only the islands but the banks and guyots of Macaronesia constitute refugia for ancient as well as more recent forms, some of which may stem back to the late Mesozoic.

Rare and new East African leucosiid crabs.

A small collection of East African leucosiid crabs, preserved in the crustacean collection at the Museo di Storia Naturale dell'Università di Firenze, Italy, was examined. Of these, one, Cryptocnemus grandidieri A. Milne-Edwards 1865, collected in 1864 by Alfred Grandidier in Zanzibar and known only from the single type specimen, is redescribed and illustrated. The others are new to science: one each are included in Leucisca MacLeay, 1838 and Nobiliella Komatsu Takeda, 2003. These new species are described and illustrated, and their affinities with allied taxa discussed.

Here and there: a preliminary note on the prevalence of an alien rhizocephalan parasite at the southern and northern limits of its introduced range.

The Erythrean invasive swimming crab Charybdis longicollis established dense populations in the Levantine Basin of the Mediterranean Sea in the mid 20th century. The crabs were subsequently parasitized by the rhizocephalan Heterosaccus dollfusi , itself an Erythrean alien. In May 2008, the crab populations were sampled at the southern (Israel) and northern (Turkey) limits of its introduced range. The prevalence of infection was 3 times as high, and multiple externae-bearing hosts more than 4 times as many, in Israeli waters as in Turkey. It seems that off the Israeli coast, the water temperature permits the synchronous ontogenetic development of both host and parasite, ensuring the availability of plentiful young, recently-molted, prospective hosts for infection by the short-lived parasite cypris. It is possible that the lower water temperature off Antalya (Turkey) may affect the timing of ontogenetic development of one species or the other, or increase the mortality of infected hosts, resulting in drastically reduced parasite prevalence.