Giuseppe Manganelli

A tropical fish community in thermal waters of southern Tuscany

In a small stream of southern Tuscany (Fossa Calda), fed by hot springs, we discovered a fish community dominated by tropical species, some of which have never previously been reported in Euro-Mediterranean natural freshwater environments. The aim of our research was to ascertain whether the three most abundant and widespread species (Amatitlania nigrofasciata, Hemichromis sp. and Oreochromis niloticus) have become established. Analysis of size class distribution and growth curves showed that the populations of these species are quite large and made up of juveniles, subadults and adults, as is the case in self-sustaining populations. These fishes were probably released intentionally, since they are widely used in aquariums and aquaculture and their survival in Fossa Calda was possible because of the constant high temperature of thermal waters. Spread to other streams seems unlikely. In fact, at some distance from the hot springs, where water temperatures are lower, populations of the tropical species were small.

Peri-tyrrhenian phylogeography in the land snail Solatopupa guidoni (Pulmonata)

ABSTRACT The land snail Solatopupa guidoni has an interesting disjunct distribution in the peri-Tyrrhenian area, with a few scattered populations in Sardinia, Corsica, and Elba Island. The species is strictly bound to limestone and has poor dispersal capacity. Here, we used sequences of two mitochondrial genes, cytochrome oxidase I (COI) and 16S rRNA (16S), to reconstruct the species phylogeography. The study is based on nine of the 13 populations reported in the literature. Phylogenetic methods and nested clade analysis failed to retrieve reciprocally monophyletic lineages on each island. Sardinian and Elba Island populations were found to be embedded within those of Corsica. These results contrast with previous phylogeographic studies of other organisms with similar distribution patterns, showing major phylogeographic breaks between islands. Molecular clock estimates suggest that species diversification occurred less than 2.5 Myr ago, in line with a previous study that dated the split of S. guidoni from its continental sister species at 3–5 Myr. Corsican populations can be tentatively sorted into two haplo-groups. A first group includes haplotypes found in central inland Corsica only, whereas haplotypes found in northern coastal locations cluster in a second haplo-group. The latter also includes Sardinian and Elba Island populations. Molecular data indicate that a combination of vicariance and dispersal events provide the best explanation of the distribution of this species.

Historical biogeography of Tyrrhenian land snails: The Marmorana–Tyrrheniberus radiation (Pulmonata, Helicidae)

The few studies available on Tyrrhenian land snails support high diversification in the Italian Peninsula and groups structured mainly by vicariant events. Here we investigated the phylogeny of a conchologically diversified group of Tyrrhenian land snails assigned to the genera Marmorana and Tyrrheniberus. We constructed a molecular phylogeny by sequencing two commonly used mtDNA genes (cytochrome oxidase I and the large ribosomal subunit). We also carried out conchological and anatomical analysis. Morphological (shell and genitalia) and genetic data (mitochondrial genes) showed paraphyly of Marmorana. Plio-Pleistocene events in the Tyrrhenian area may have structured relationships between species at regional scale while isolation by distance probably played a role in diversification between populations on a local scale. Continental populations experienced dispersal during interglacial periods and fragmentation and reduction during the dry cold climatic phases. Areas inhabited by Apennine Marmorana could represent relict and/or glacial refugia, with extinction in some areas along the Apennines and survival in the south. The results support a reassessment of taxonomy both at genus and species level and call for further analysis.

The fine structure of the mature spermatozoon of Onchidella celtica (Cuvier) (Mollusca: gastropoda) and its phylogenetic implications

The spermatozoon of Onchidella celtica shows many peculiar features. The acrosome is formed by an apical vesicle and a pedestal consisting of a principal body which is flanked by two electron-dense elliptical elements. The mitochondrial derivative consists of three different components: peripheral layers of paracrystalline material, concentric cisterns, and two cylindrical compartments. The 9 + 9 + 2 axoneme shows 9 small deposits of glycogen granules in correspondence with the axonemal “spokeheads,” and a small assembly of possibly proteic material lying close to the two central tubules. Another intraaxonemal deposit of glycogen granules is present at the level of the “glycogen piece.” Most of the observed features are in substantial agreement with those of another species of the Onchidiidae. This confirms the constancy of sperm structure among the members of a single family of the Gastropoda.

A question of time: the land snail Murella muralis (Gastropoda: Pulmonata) reveals constraints on past ecological speciation

The lively debate about speciation currently focuses on the relative importance of factors driving population differentiation. While many studies are increasingly producing results on the importance of selection, little is known about the interaction between drift and selection. Moreover, there is still little knowledge on the spatial‐temporal scales at which speciation occurs, that is, arrangement of habitat patches, abruptness of habitat transitions, climate and habitat changes interacting with selective forces. To investigate these questions, we quantified variation on a fine geographical scale analysing morphological (shell) and genetic data sets coupled with environmental data in the land snail Murella muralis, endemic to the Mediterranean island of Sicily. Analysis of a fragment of the mitochondrial DNA cytochrome oxidase I gene (COI) and eight nuclear microsatellite loci showed that genetic variation is highly structured at a very fine spatial scale by local palaeogeographical events and historical population dynamics. Molecular clock estimates, calibrated here specifically for Tyrrhenian land snails, provided a framework of palaeogeographical events responsible for the observed geographical variations and migration routes. Finally, we showed for the first time well‐documented lines of evidence of selection in the past, which explains divergence of land snail shell shapes. We suggest that time and palaeogeographical history acted as constraints in the progress along the ecological speciation continuum. Our study shows that testing for correlation among palaeogeography, morphology and genetic data on a fine geographical scale provides information fundamental for a detailed understanding of ecological speciation processes.

Population Dynamics of an Urban Population of the Land Snail Marmorana serpentina (Gastropoda: Pulmonata)

Spatial distribution, population structure, and dispersal patterns are fundamental characteristics of species. When the area occupied by a population far exceeds the dispersal ability of individuals, random mating cannot be assumed over the entire population. Wright (1946) introduced the concept of “neighbourhood” for cases in which individuals have only a limited number of potential partners, their neighbours. Neighbourhoods are restricted areas where random mating is likely. Study of the population structure and understanding of speciation processes depend on accurate data on movement patterns, dispersal capacity, and density (Parmakelis & Mylonas, 2004). Land snails are particularly subject to population subdivision and geographic structuring due to their low dispersal capacity and frequent restriction to calcareous substrata. Active dis-

Litthabitella chilodia (Westerlund, 1886) in Italy (Gastropoda: Prosobranchia: Hydrobiidae)

Bythinella opaca pollinensis Bacci (1952) is herein regarded as a junior synonym of Litthabitella chilodia (Westerlund, 1886). Litthabitella Boeters, 1970, is a genus of hydrobiid prosobranchs characterized by: penis apex bifid, divided into apical lobe and tip of penis proper; one–four irregularly shaped glandular swellings on ventral side of apical lobe and penis close to base of lobe; well developed bursa copulatrix; two seminal receptacles, proximal (RS2) smaller than distal (RS1). At present it includes only the type species L. chilodia present in the western Balkans, Ionian islands and southern Italy. Paludinella elliptica Paladilhe, 1874, from the Pyrenees, once attributed to Litthabitella, still has uncertain taxonomic relationships. The current subdivision of L. chilodia into L. chilodia chilodia and L. chilodia ionica (Schütt, 1980) is rejected. Examination of the type material of the latter from the island of Corfu, showed that it includes two different taxa, one of which (the holotype) is a species of Belgrandia and the other L. chilodia. Due to the absence of anatomical data, the taxonomic status of Belgrandia ionica (Schütt, 1980) is still uncertain. Italian populations of L. chilodia are characterized by wide variation in shell shape and size and one population, living in a small brook in the cave Grotta del Tasso in Apulia, has two distinct coexisting shell morphs, almost without intermediates.

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.

Recent expansion and relic survival: Phylogeography of the land snail genus Helix (Mollusca, Gastropoda) from south to north Europe.

Little is known about the evolutionary history of Helix, despite the fact that it includes the largest land snails in the western Palaearctic, some of which (e.g. H. pomatia Linnaeus, 1758) are valuable human food. We compared two groups of Helix with apparently contrasting evolutionary histories: the widespread species H. pomatia and the group distributed along the Italian Apennine chain, a relatively unknown set of species with a restricted distribution over a range of altitudes. To reconstruct the evolutionary trajectories of these two groups, we analysed morphological (shell and genitalia) and molecular characters (mitochondrial and nuclear markers) in a total of 59 populations from northern and central Europe (H. pomatia) and along the Apennine chain (various species). We also reconstructed the phylogeny and the evolutionary history of the genus by combining our data with that currently available in the literature. We found that spatial changes did not merely imply fragmentation of populations, but also implied environmental changes (woodlands vs. grasslands) that may have triggered the observed phenotypic diversification. We also found that Anatolia is the ancestral range of Helix and is therefore an important area for the Palaearctic diversity. The results provide insights into the evolutionary history of species richness and more generally into the processes that may have shaped the distribution and diversification of these organisms across Europe and the peri-Mediterranean area.