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Among ten adult specimens of the Madeiran endemic land snail Leptaxis simia (Férussac, 1832) (Gastropoda: Hygromiidae), harvested from their natural environment, kept in the laboratory, a single clutch of 110 eggs was reared, and the mortality, growth and reproductive capacity of hatchlings over a 1240-day period were monitored. Of 70 hatchlings, 34 survived to complete shell growth at around 640 days. Growth was rapid, and mortality high in the early stages; growth slowed, and mortality was very low as the full size was approached. Snails kept singly failed to lay any eggs. Among those with potential mates, only three clutches were produced, one of which yielded no hatchlings. Clutches were produced at least five months after shell growth was complete. Mortality increased sharply after the onset of sexual maturity, and the oldest snail survived for three and a half years. The apparently very strictly semelparous mode of reproduction, delayed sexual maturity and a relatively long period of juvenile growth are discussed in relation to other species and to the practical problems of rearing potentially endangered species in captivity. [ABSTRACT FROM AUTHOR]

A countrywide data set of 1048 samples of the European land snail Cepaea nemoralis (L.) from Poland was assembled from both published and unpublished sources. Analyses of shell colour and banding polymorphism revealed distinctive patterns of variation. While the frequency of brown shells showed a clear geographical pattern related to climate, other morphs showed no such clear trends. Variation among populations was great, but little of this could be accounted for by variation among regions. Spatial autocorrelation was generally restricted to very short distances, of the order of 20 km or less. Variation with habitat was found in the form of an excess of brown shells in shaded habitats and an excess of yellow and yellow effectively unbanded shells in open habitats, although this was not universal. The data suggest that cases of long-distance, passive dispersal followed by more local spread account for much of the variation, and that strong selection related to habitat may be obscured by different sources of populations within a few kilometres of each other. The data are now available to track changes over time. [ABSTRACT FROM AUTHOR]

Previously in this journal, Altaba (2015) presented an original hypothesis on the dispersal of small wetland snails in Central Europe after the Last Glacial Maximum, based on the discovery of rare species of the genus Vallonia at the foot of the Devín Hill (Slovakia). On the basis of the evidence available to us, it is our opinion that the existence of Vallonia declivis, Vallonia suevica, Vallonia enniensis, and Vallonia tenuilabris at Devín Gate has not been established, and that the hypothesis advanced in Altaba (2015) is therefore unsubstantiated by hard evidence. [ABSTRACT FROM AUTHOR]

Twenty-nine forest sites in six sampling areas in the Banat region of Romania, adjacent to Serbia, were sampled to obtain inventories of their snail faunas and to make comparisons between these and previously studied faunas in the mountains from the Sudetes in the north-west to the Southern Transylvanian Carpathians in the south. 65 species were recorded overall, with between 13 and 33 at individual sites. Among the six sampling areas that on Schist rock at high altitude differed markedly from the others, and contained mainly species also found in Carpathian forests further north. The remainder, mainly on limestone, also differed among themselves, but contained more species endemic to the region or regions to the south, together with those found mainly in open rocky habitats further north. Some species and subspecies were restricted to particular areas within the region, and although ecological factors accounted for some of these differences, they did not explain all of them. The faunas were differentiated from those in the Carpathians further north, and showed a greater affinity to those from countries to the south. These patterns indicate a transition between northern regions with locally rich but regionally poor forest faunas and those of the Balkans and Mediterranean with many restricted endemics that survived the climatic fluctuations of the Pleistocene in situ. Such faunas are no richer at site level than those from further north, but differ more among themselves even when environmental conditions are similar. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, ●●, ●●-●●. [ABSTRACT FROM AUTHOR]

Although present since the mid 19th century, the introduced snail species Cepaea nemoralis has spread extensively in Göteborg, mainly in the last two decades. Early samples show the predominance of yellow-shelled morphs, but in modern populations pink shells predominate. There is great variation in morph frequencies among modern populations with high values of FST, and with no relationships to habitat. The patterns shown resemble those seen in Sheffield (UK), a city also colonised over a similar time period, but differ from those seen in regions where the species has been established for much longer. The combination of early and recent records suggests not only that founder effects play a large part in determining morph frequencies, but that present populations derive from multiple colonisations from different sources. [ABSTRACT FROM AUTHOR]

The globally significant Caucasus hotspot of biological diversity holds a rich and largely endemic fauna of land molluscs. Georgia holds the majority of these regional endemics. Land molluscs are particularly sensitive indicators of habitat quality and faunal diversity. In this study, we examine the extent to which the existing network of protected areas (PAs) within Georgia captures the hotspots of endemic molluscan diversity. We collected and mapped the records of Georgian and Caucasian endemic species onto a 20 × 20 km2 UTM grid to identify the most important endemic areas in Georgia. We related these to the existing network of PAs. Less than half of the richest grid cells included significant PAs. Although those endemics with the smallest known ranges were better protected than the remainder, the incomplete state of knowledge means that our estimates of existing protection are surely optimistic. To date, the designation of PAs in Georgia has not used distributional data for invertebrates, although elsewhere they have been shown to be an effective aid to planning and management for conservation. Further surveys of molluscs and their monitoring in existing PAs can and should inform a systematic conservation strategy in Georgia. [ABSTRACT FROM AUTHOR]

The land snail faunas of 26 forest sites and two open rocky sites in the Crimean Mountains were sampled in 2011. Of the 40 species found within the forests (about half the known fauna of Crimea as a whole), 28 were species with wide western Palaearctic distributions, and only eight were endemic to Crimea. While there were significant differences in the faunas of different sampling areas, these seemed to be a consequence of ecological differences among them rather than a product of geographical isolation and differentiation. Endemic species were large, and not entirely restricted to forest; known endemics not found in these forests are mainly typical of more open habitats. There is no local radiation of small species living in damp forest litter, as with Leiostyla species in the Transcaucasian forest refugium, and families such as the Clausiliidae with many endemic forest species in both Transcaucasia and the Carpathians are sparsely represented. The one endemic clausiliid genus, Mentissa, occurs in open as well as in wooded habitats. The present faunas are rather poor considering the soil conditions and climate, and the forests hold widespread species often associated with open habitats elsewhere. While there is evidence that these mountains provided a refuge for many animals and plants during glacial episodes further north, the forest snail fauna suggests that full forest cover did not survive throughout the Pleistocene. Rather, the present fauna contains endemics that survived in other habitats and widespread species with good powers of passive dispersal. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109, 424-433. [ABSTRACT FROM AUTHOR]

The shell-colour and banding polymorphism of Cepaea hortensis has attracted less attention than that of its congener C. nemoralis. While the Evolution Megalab acquired many records of its variation, those submitted by amateurs were unreliable, and hence it was impossible to analyse possible changes over time. Nevertheless, the Megalab database reveals many aspects of variation in C. hortensis. There is less polymorphism for shell colour than in C. nemoralis and the pattern of geographical variation is different; in some cases trends go in the opposite direction. Polymorphism is greatest near the centre of the range. Variation with habitat shows trends similar to those in C. nemoralis, although the absence of data on band fusions limits the extent to which such variation can be detected. While it is clear that natural selection influences morph frequencies in many cases, the differences in patterns seen in these two very similar species indicate that appearance alone does not determine the range of frequencies observed. [ABSTRACT FROM AUTHOR]

Populations of the polymorphic land snail Cepaea nemoralis ( L.) from Deepdale, Derbyshire, UK, sampled in 1965-67, showed a pattern of area effects, with steep clines among groups of populations differing in shell colour and banding morph frequencies. In 2010, most of these populations were resampled. In particular, a continuous transect made in 1967 of 42 quadrats (18.34 × 18.34 m) across a steep cline in several morph frequencies was completely resampled. In the dale as a whole, yellow shells had increased in frequency. In the transect, the frequencies of banding morphs showed no significant changes, although colour morphs showed some changes. Pink shells had increased in frequency in a section in which scrub had developed, and brown shells had increased in frequency in the area in which they had originally been at the highest frequency. In each case, the selection coefficients were of the order of 4%. Yellow had increased elsewhere. Nevertheless, both in the dale as a whole and in the transect, the pattern of geographical change in morph frequencies had remained essentially the same. Estimates of migration based on previous studies of marked snails and on modelling of the effect of drift and migration suggest that, regardless of whether the cline is a product of differential selection or of the gradual merging of previously separate founding populations, it has been in existence for a long time, and that migration occurs over greater distances than estimated from direct observation on marked snails. Although we can demonstrate that selection has occurred, the origin and maintenance of the cline and others similar to it remain in doubt; the development and maintenance of polymorphism in this species may require consideration of several processes operating on different time scales. © 2012 The Linnean Society of London [ABSTRACT FROM AUTHOR]

Changes in morph frequency over time in sand-dune populations of Cepaea nemoralis in the British Isles have been examined using the Evolution Megalab database. Frequencies in colonies on a sand dune at Berrow, Somerset were estimated in 2008-9. This extends a survey started in 1926 by A. E. Boycott and C. Diver and continued in the mid-20th Century by B. C. Clarke and J. J. Murray. An increase in the frequency of the mid-banded morph, noted in earlier work, has continued. The apparent decrease in brown was not confirmed but the yellow frequency has increased. At a range of dunes in the British Isles, comparisons between data from the mid-20th Century and the early 21st Century indicate an increase in yellow and mid-banded morphs and a decrease in banding and brown morphs. These results differ from the overall trends derived from Europe-wide comparison of early data with Evolution Megalab data, in which banded and mid-banded increased in frequency, whereas there was no overall change in yellow. The general pattern of regional variation has been retained, although there is also high heterogeneity between samples, suggesting that a variety of factors are involved in explaining the changes. The mean shifts in frequency are consistent with climatic change over the period. Dunes are probably the most likely habitat in which to detect such a change. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 108, 315-322. [ABSTRACT FROM AUTHOR]

Aim We collate and analyse data for land snail diversity and endemism, as a means of testing the explanatory power of the general dynamic model of oceanic island biogeography ( GDM): a theoretical model linking trends in species immigration, speciation and extinction to a generalized island ontogeny. Location Eight oceanic archipelagos: Azores, Canaries, Hawaii, Galápagos, Madeira, Samoa, Society, Tristan da Cunha. Methods Using data obtained from literature sources we examined the power of the GDM through its derivative ATT2 model (i.e. diversity metric = b1 + b2Area + b3Time + b4Time2), in comparison with all the possible simpler models, e.g. including only area or time. The diversity metrics considered were the number of (1) native species, (2) archipelagic endemic species, and (3) single-island endemic species. Models were evaluated using both log-transformed and untransformed diversity data by means of linear mixed effect models. For Hawaii and the Canaries, responses of different major taxonomic groups were also analysed separately. Results The ATT2 model was always included within the group of best models and, in many cases, was the single-best model and was particularly successful in fitting the log-transformed diversity metrics. In four archipelagos, a hump-shaped relationship with time (island age) is apparent, while the other four archipelagos show a general increase of species richness with island age. In Hawaii and the Canaries outcomes vary between different taxonomic groups. Main conclusions The GDM is an intentionally simplified representation of environmental and diversity dynamics on oceanic islands, which predicts a simple positive relationship between diversity and island area combined with a humped response to time. We find broad support for the applicability of this model, especially when a full range of island developmental stages is present. However, our results also show that the varied mechanisms of island origins and the differing responses of major taxa should be taken into consideration when interpreting diversity metrics in terms of the GDM. This heterogeneity is reflected in the fact that no single model outperforms all the other models for all datasets analysed. [ABSTRACT FROM AUTHOR]

Sampling of land snails in 19 small sites on Santa Maria (Azores) in 2008 and 2011 yielded a total of 52 species; 26 were Macaronesian endemics, of which 23 are restricted to the Azores. These represent nearly all the described endemic fauna. Forest faunas were the richest and contained the highest proportion of endemic species. Widespread European species were the major components of assemblages in open habitats, subject to greater human disturbance, while secondary or heavily disturbed forests were intermediate. A small suite of endemic species showed no habitat preference and may represent a fauna living in relatively open conditions prior to human occupation. Within forests, congeneric species frequently occur in the same site. All seven endemic Oxychilus species recorded occurred in a single site; there is no evidence of allopatric replacement or restricted distribution other than that imposed by habitat. This may reflect the age of the island, the oldest in the archipelago. Nearly all forest endemics are found near the summit of the highest peak, a small area vulnerable to habitat destruction or climate change; even without these, there may be an extinction debt to be paid in the absence of conservation measures. [ABSTRACT FROM AUTHOR]

The Evolution Megalab database on the shell polymorphism of Cepaea nemoralis contains data on the majority of populations sampled over the last 100 years. Here, we use the database to examine geographical variation in the strength of the known relationship between morph frequencies and habitat. Unique pairs of samples from woodland and the nearest open habitat (hedges and grassland) are used to analyse the direction and magnitude of differences in morph frequencies. Shell colour shows stronger and more consistent variation with habitat than do banding patterns, yellow shells being at higher frequencies in open habitats than in woods. There is, however, marked geographical variation in this relationship, which is stronger in southern England and northern France than elsewhere. In some regions there is no evidence of any effect. Only in southern England are there significant associations between habitat and banding, with unbanded shells being at higher frequencies in woods than in open habitats. Within Great Britain a more refined analysis shows that the effects of habitat are evident mainly in areas of ancient countryside, in which many woods suitable for the species have existed for centuries. Less stable areas frequently exhibit ‘area effects’ in which variation does not relate to habitat. In a smaller set of pairs, such regional variation is not apparent in Germany. Earlier disputes about the role of drift and natural selection in determining patterns are in part a reflection of the region in which studies were carried out. The Megalab database does not cover all aspects of the polymorphism. In particular, band fusions are not recorded. The lack of evident effect in many regions does not demonstrate that there is none; more data and some knowledge of historical changes in habitats might reveal trends not apparent in this limited and conservative study. [ABSTRACT FROM PUBLISHER]

Forty-three forest sites in seven sampling areas in mountainous parts of Transylvania were sampled to obtain inventories of their snail faunas, and to make comparisons between these and the faunas of similar sites further north along the Carpathian chain. Sampling areas ran from close to the Ukrainian border in the north to Retezat in the south-west. Altogether, 83 species were found, as well as between 19 and 40 species at individual sites. Sites within the same sampling area had more species in common than in among-area comparisons, although differences between areas did not relate to the distance between them. Such differences appear to be related more to ecological factors than to geography. Faunas of all areas were very similar to those recorded from the Polish and Ukrainian Carpathians; distance from these northern faunas had little effect on similarity. More broadly, the fauna of these forests shows a much greater affinity to those of countries to the north than to those of countries to the south. Despite the survival of forests through the last glacial period of the Pleistocene, and the greater proximity to potential Mediterranean refugia, these faunas appear to be mainly a subset of those found further north. They represent a rather small proportion of the known Romanian fauna, in which there are many endemics restricted to other habitats. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104, 471-479. [ABSTRACT FROM AUTHOR]

Thirty forest sites in Georgia were sampled to obtain inventories of their land snail faunas. The sites, in nine sampling areas, ranged from Batumi near the Turkish border to Lagodekhi near the Azerbaijan border, and included parts of both the Lesser and Greater Caucasus mountains and the Colchic lowlands. Abundance was generally low, and most sites held less than 20 species. Ninety species were found overall. Although sites within some sampling areas had very similar faunas, the overall levels of similarity among sites and sampling areas was low, especially when compared with similar forests from northern central Europe. Both climate and geographical position affected similarity: although these were correlated, independent effects of each were detected, and the effect of position alone was strongest. Despite this effect, most species have ranges extending into Turkey or Ciscaucasia, a few have very limited ranges, and there is no evidence of patterns of allopatric replacement among congeners. These patterns resemble those seen in faunas from forests in lower latitudes, and suggest a slow build-up of regional diversity by differentiation in situ, without the repeated restrictions to a multiplicity of small refugia that are characteristic of areas where fluctuations in aridity are important. The refugium has remained isolated, and has contributed little to the Holocene recolonization of areas further north. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, , 239-250. [ABSTRACT FROM AUTHOR]

The shell colour and banding polymorphisms in urban populations of Cepaea snails were studied in Sheffield (England) and Wrocław (Poland), which are two cities of similar size. Both Cepaea nemoralis and Cepaea hortensis were found in Sheffield, but only C. nemoralis was found in Wrocław. In neither city was variation with habitat apparent, nor was there evidence of large-scale geographical patterns. Spatial autocorrelation analyses revealed only vaguely defined local clusters. There was a greater degree of among-population variation in Sheffield, and more cases of extreme frequencies and low levels of polymorphism. Wrocław populations were more uniform and highly polymorphic. These differences can be related to the history of these snails in each city. Sheffield has been colonized mainly in the last 20 years, and some parts of the city with apparently suitable habitat remain unoccupied. Leptokurtic dispersal of small propagules followed by local spread appears likely. Values of FST resemble those seen in districts elsewhere with ‘Area Effects’. Although there are ancient woodlands within the city, they have been colonized too recently for selection to achieve a new balance. Wrocław has held Cepaea populations for at least 100 years, and they are denser and more continuous. Shaded habitats are recent and temporary; the overall pattern of variation matches that seen in open habitats in districts elsewhere in which variation with habitat is apparent, and values of FST also correspond. Population history and the character of dispersal clearly affect the patterns of variation observed. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 97, 27–39. [ABSTRACT FROM AUTHOR]

Cepaea hortensis (Gastropoda: Pulmonata) populations in Hertfordshire, England, originally sampled in 1964–66, and sampled again in 1990, were sampled in 2007. Although the general pattern of shell colour and banding polymorphism remained stable, a significant trend for a reduction in the frequency of yellow shells in sites from valley bottoms, as observed in 1990, continued through to 2007. In both 1964–66 and 1990, populations in valley bottoms had higher frequencies of yellow shells than those on the sides, but this topographical relationship had effectively disappeared by 2007. The relationship had been explained in terms of low temperature extremes in valley bottoms in cold, anticyclonic conditions. Its decay is associated with much warmer winter conditions prevailing in the 3 years previous to both resurveys, compared with those before the original survey. The frequency of unbanded shells also increased over the period, but this change showed no topographical variation, and thus it is not possible to assign it to a particular cause. The low levels of variation between samples from the same habitat and the absence of present topographical relationships conceal the occurrence of powerful climatic selection, which is revealed only by repeated surveys. The conditions in which such changes might be detected are discussed. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95, 53–61. [ABSTRACT FROM AUTHOR]

Aim: Island biological communities are considered to comprise non‐random assemblages from surrounding source pools, but whether they converge towards predictable structural properties remains unclear. Here, we (i) test whether insular communities of land snails converge towards similar functional and/or taxonomic properties and (ii) evaluate whether island functional diversity is determined by island biogeographical characteristics such as area and distance to the pool as well as human‐related variables. Location: Sixty‐six continental Aegean islands. Taxon: Land snails. Methods: We compiled a database of two morphological traits with functional significance (shell height and width) for 163 island species and 1529 species from the major species pools. We quantified inter‐specific morphological dissimilarity between pairs of islands (turnover), using a modified index of the mean nearest taxon distance. We tested for functional and taxonomic convergence using null models and assessing whether overall mean turnover among islands and pairwise island‐by‐island turnover were lower than expected by chance. We performed multiple regression analyses to test whether functional diversity metrics scale with island biogeographical characteristics and human‐related variables. Results: Our analyses provide strong evidence that communities of land snails across the Aegean islands converge towards non‐random functional properties and taxonomic structure. At the island level, a wide range of different shell shapes is observed, indicating greater functional richness than expected by chance. Regression analyses showed that island area is the only efficient predictor of functional diversity, indicating that available ecological/resource space is of central importance in driving the assembly of different shell shapes. Main Conclusions: Our findings, consistent with previous studies of other taxa from oceanic islands, highlight that island species communities are not randomly assembled and display convergence in their functional and taxonomic composition. Integrating functional diversity metrics within biogeographic analyses has the potential to further our understanding of island biodiversity patterns. [ABSTRACT FROM AUTHOR]

Melanopsidae were collected from 23 localities in central and south-eastern Europe, the Aegean Islands and Israel. This study considered Melanopsis from the Aegean Islands, the Peloponnese and Israel, and Esperiana esperi , Holandriana holandrii and Microcolpia from continental Europe. Shells and radulae were described and illustrated, showing continuous variation of shell characters and differences in radulae among genera. Phylogenetic analyses were conducted on single-locus datasets (COI , 18S, 28S, ITS2 and H3) and on a concatenated dataset. Molecular data showed a differentiation not paralleled in morphology, reflecting morphostatic evolution. In all species with ribbed shell-forms, the ribbed and unribbed forms did not differ genetically. Within Melanopsis , four clades representing five species were distinguished. Melanopsis buccinoidea is found in Khios and Lesbos Islands, M. astropaliae in Naxos, Samos and Tinos Islands, M. wagneri in Rhodes Island and the Peloponnese, and M. costata and M. saulcyi in Israel. Molecular results and the ICZN rule of priority restrict the range of M. buccinoidea to the North Aegean Islands. ' Melanopsis ' parreyssi belongs to the genus Microcolpia. Esperiana esperi belongs to a clade separate from Microcolpia. [ABSTRACT FROM AUTHOR]

The polymorphic land snail Cepaea hortensis was introduced to the city of Sibiu, central Romania, in the first decade of the 20th century and has spread widely across the city. A total of 97 locations were examined in 2017 across the city to determine the habitat preferences and variation in shell size, shape, colour and banding polymorphism of C. hortensis, and to relate these to the same features in the likely source population from Mannheim, Germany, and the first established population in Sibiu. We found that C. hortensis was largely restricted to sites with some woody vegetation cover and showed a marked preference for abandoned and overgrown private gardens. Mean adult shell size in present-day populations was almost always smaller than in both the presumed population of origin from Germany and the first recorded population from Sibiu. Populations showed a wide range of variation in frequencies of shell colours and banding morphs. This variation was not related to habitat or cover, and there was no evident geographical structure in the patterns. Comparisons with a smaller-scale sampling in 2004/5 showed that some populations had gone extinct, some remained stable and in some morph frequencies had changed drastically, but in no consistent direction. These results are similar to those obtained for the related species C. nemoralis in comparable circumstances, but differ from those obtained from regions where C. hortensis is long established and where habitats have been stable. The patterns we observed most likely reflect the effect of passive dispersal by humans, genetic drift and founder effects. [ABSTRACT FROM AUTHOR]

Late Quaternary deposits containing fossil snail shells were sampled from nine sites on Deserta Grande and three on Bugio, two of the three Desertas Islands in the oceanic Madeiran archipelago. In total, 3,432 shells representing 45 species or subspecies were retrieved. Calibrated amino acid racemization yielded ages ranging from >45 to 6 ka, with variation by site often confounded by reworking of mostly colluvial deposits. The assemblages found are compared with the extant fauna, itself a subject of intensive recent study. Of the 45 taxa, 18 are apparently extinct, and a further 5 no longer survive on the Desertas. A similar pattern emerges when each island is considered separately. The level of local extinction (c. 50%) is greater than seen on the larger, nearby islands of Madeira and Porto Santo. There are few endemic species in the extant fauna not represented in the fossil assemblages, but there are a number of possibly adventitious species, some with wide distributions in Europe. There is little evidence of faunal change within the limits of the age range available, and extinction seems to be concentrated in the later Holocene. It is attributed to the massive habitat destruction that occurred subsequent to human occupation from the 15th century CE onwards. The study emphasizes the depauperate nature of many extant island faunas subject to human disturbance. [ABSTRACT FROM AUTHOR]

In this article, the author discusses the findings of the study which examines the effects of land-snail fauna of 21 lowland rain forest in Sri Lanka. They assess that it highlights several crucial aspects of the fragmentation and relaxation issue, such as the findings that fragment age is a determinant of the fragmentation-related changes in community composition. They add the study's determination that in most landscapes, it is the productive or most accessible areas that are deforested first.

Aim: Morphological and taxonomic diversity are intuitive measures of biological diversity. Previous studies have shown discordance between these measures at large spatial and temporal scales, but the implications of this pattern for the underlying processes are not understood. Using oceanic archipelagos as spatial units, we examine potential links between the morphological and taxonomic diversity of their land snail faunas in a biogeographical framework. Location: Eleven major oceanic archipelagos. Methods: For each archipelago, we assembled lists of indigenous land snail species, classified by family and genus, with shell height and width for each species (1723 species in total). We used biogeographic and climatic variables as potential predictors of diversity patterns. We employed regression analyses to evaluate (1) whether morphological diversity scales with taxonomic diversity at the species, genus or family level, and (2) whether morphological and taxonomic diversity correlate similarly with biogeographic/climatic factors. We also assessed which taxonomic level contributes most to morphological variation within archipelagos. Results: Morphological diversity across archipelagos was strongly related to genus but not species richness. Within archipelagos, morphological variation reflected differences among genera and families but not species. Species richness was best explained by archipelago area, but morphological diversity was not significantly related to any of the physical features of archipelagos. Main conclusions: Across archipelagos, species richness and morphological diversity of land snail faunas are decoupled. The relationship between species richness and the available ecological space (captured mainly by area) indicates the prevalence of niche-based processes while, for morphological diversity, the strong conservatism of morphology at the genus level suggests the presence of diversification-based limits. Assuming genera effectively reflect diversification, our findings indicate that morphological space on oceanic archipelagos depends primarily on the number of evolutionary units that have colonized and/or diversified through time. [ABSTRACT FROM AUTHOR]