Andrea Benocci

The role of dispersal and local environment in urban land snail assemblages: an example of three cities in Central Italy

Ecologists increasingly appreciate the central role that urban biodiversity plays in ecosystems, however much urban biodiversity is neglected, especially some very diverse groups of invertebrates. For the first time in southern Europe, land snail communities are analysed in four urban habitats along a geographical gradient of three cities, using quantitative methods and assessing the relative roles of local environmental conditions (“distance from sea”, “distance from city centre”, “vegetation cover”) and spatial effects by principal coordinate analysis of neighbour matrices, redundancy analysis and variation partitioning. A total of 53 species was recorded, a richness similar to that of natural areas. At habitat level, species richness did not show a clear increasing trend from more to less urbanized habitats, but rather a homogeneous pattern. At city level, study areas hosted rather heterogeneous species assemblages and biotic homogenization did not seem to have any impact; indeed, only three species could be considered alien. Variation partitioning showed that land snail communities were mostly structured by environmental factors, even when spatial structures independent of measured environmental variables were included: “vegetation cover” and “distance from city centre” were the environmental variables that explained most of the variation in species composition. The lack of strong spatial structure also unexpectedly suggested that transport by humans aids dispersal of organisms with low mobility, which are usually limited by spatial constraints in natural environments. These results provide ecological and conservation implications for other invertebrate groups, suggesting to set priorities in management strategies that include habitat conservation at local scale.

A Survey of Vitrinid Land Snails (Gastropoda: Pulmonata: Limacoidea)

ABSTRACT There is general agreement that the vitrinids, a mainly Palaearctic group of semislugs, are higher stylommatophorans, but uncertainty still exists about their relationships. We therefore conducted a phylogenetic study based on morphological characters to determine relationships between genus-group taxa and to test monophyly and revise current taxonomy. Eighteen genus-group taxa — those listed as valid in the recent literature plus the new genus Azorivitrina —were considered using an exemplar approach, with individual species as terminals to avoid a priori assumption of monophyly. At least two species, one of which was the type species, were examined when possible. Phylogenetic analyses were performed using different outgroups consisting of a selection of western Palaearctic limacoidean genera (data partition I, DPI: outgroup consisting of Euconulus, Deroceras, Oxychilus, Tandonia, Vitrea and Troglaegopis; DPII: outgroup Euconulus, Oxychilus, Vitrea and Troglaegopis; DPIII: outgroup Euconulus and Oxychilus). Different approaches were used: parsimony analysis (MP: using PAUP* 4.0; AP: TNT software) and bayesian inference (BI: using MRBAYES). Phylogeny analysis generally had low resolution. The parsimony analysis using implied weights (TNT software) provided the best results (AP found 11 supported clades, MP 11 and BI 8). It did not support monophyly of most genus-group taxa or the monophyletic groups found by Hausdorf (1995, 2002) and Alonso et al. (2000), or the subfamilies and tribes established by Schileyko (1986, 2003), or the family Vitrinidae when the outgroup consisted of a large selection of limacoidean taxa. Support was only found for Canarivitrina, Guerrina, Oligolimax and Vitrinobrachium and some support for Arabivitrina and Azorivitrina, On the contrary, no support was found for Eucobresia, Insulivitrina and Phenacolimax, or for Plutonia sensu Alonso et al. (2000). The most resolved group (but with low support values) was a clade including species of Oligolimax, Sardovitrina, Semilimacella and Vitrina supported by exclusive disposition of the penial retractor above the right ommatophore retractor. These results indicate that a different approach to vitrinid phylogeny and systematics is needed because morphological characters alone do not generate a realistic picture. In the meantime, we ranked the 18 genus-group taxa as distinct genera, although we are perfectly aware that some may be paraphyletic or polyphyletic. Finally we concisely surveyed all vitrinid genera, listing them in three distinct groups according to stimulator structure: vitrinids with vaginal stimulator (glandula amatoria); vitrinids with diverticular stimulator (atrial/atrial-vaginal/vaginal or penial diverticular stimulator); vitrinids without vaginal or diverticular stimulator. This approach enables easy comparison of taxa with similar distal genital structure and is not intended to have any systematic or phylogenetic value. A short diagnosis of each taxon is given together with re-description of the type species and remarks.

The biogeography of non-marine molluscs in the Tuscan Archipelago reveals combined effects of current eco-geographical drivers and paleogeography

We investigated the role of present (Recent) and historical (Pleistocene, i.e., Würmian Last Glacial Maximum) eco-geographical variables on the richness and diversity of non-marine molluscs in the Tuscan Archipelago, as well as inter-island faunal dissimilarity and relationships with source pools (Sardinia and Corsica, Tuscany). The association between species richness and present and historical eco-geographical variables were assessed with Spearman’s rank correlation test, while faunal dissimilarity both between islands and with their source pools was analyzed through beta-diversity partitioning (Sørensen index and its nestedness and turnover component) with UPGMA clustering tested with a multiscale bootstrap procedure. Non-metric multidimensional scaling in RGB color space was also used. Multiple regressions on distance matrices were then applied to explain assemblage composition between islands. Analyses were performed on all species and on all species except aliens. The overall framework showed the combined effects of current eco-geographical and paleogeographical imprints on non-marine malacofauna in the Tuscan Archipelago. However, excluding aliens, differences in species spatial turnover showed a clear correlation with Pleistocene inter-island distances, evidence of stronger historical biogeographical relationships between islands. This may indicate that widespread native species established their distribution during the Pleistocene, while alien species spread into the Tuscan Archipelago through stochastic and human-mediated dispersion events in recent times. Interestingly, Giglio’s relationships do not agree with the most accepted paleogeographical model, suggesting that this island might have been connected to the Tuscan mainland during the Würmian Last Glacial Maximum. An in-depth revision of the paleogeographic framework of the northern Tyrrhenian is therefore called for.