Biogeographical patterns of the genus Plectostoma H. Adams, 1865 (Mollusca, Gastropoda) in Sundaland’s limestone ecosystems

IntroductionThe Millettioid/Phaseoloid (MP) clade of Fabaceae is globally distributed, economically important, and highly diverse, making it an attractive system for studying biogeographic and macroecological patterns at a global scale. We conducted the first global macroecological study to map and explore the environmental drivers of the MP clade's species richness patterns.MethodsWe compiled 116,212 species occurrences (161 genera) for the MP clade and 20 environmental variables (19 bioclimatic variables and elevation). Geospatial analyses were performed to estimate species richness patterns and biogeographic heterogeneity. The effects of environmental variables on the species richness of the MP clade were measured through multiple regression models.ResultsOur study identified the megathermal regions as hotspots of species richness for the MP clade. While species distributions and richness largely fit the latitudinal diversity gradient pattern, there was a significant negative relationship between the species richness of the MP clade along the latitude and longitude. The Afrotropic biogeographic realm had the highest alpha diversity (~36%); in terms of biome types, tropical and subtropical moist broadleaf forests had the highest alpha diversity (25%), while the beta diversity revealed a high dispersal rate and habitat tracking. Furthermore, the species richness was positively influenced by multiple climatic factors, with the mean diurnal range of temperatures and precipitation in the warmest quarter having strongest influence.DiscussionOverall, the staggering species richness patterns could be explained by multiple diversity gradient hypotheses. Particularly, colder climates play a crucial role in shaping the species richness pattern by limiting the ecological opportunities for MP clade species in the higher latitudes of the Northern Hemisphere. This suggests that the species richness patterns of the MP clade can be described as "when dispersal meets adaptation." Our study provides a new basis for identifying priority regions for conservation of legumes.

This study highlights the diversity of land snails in Penang Hill, a non-limestone hill in Peninsular Malaysia. A systematic survey of land snails in Penang Hill was conducted, inventoried, and compared with those specimens collected by Stoliczka (1872, 1873) in 1869. Based on the 33 sampling plots established in this study, the differences in species composition along the elevation gradient (75 m to 770 m a.s.l.) and between three different habitats on Penang Hill were examined: disturbed forests with anthropogenic activities, undisturbed forests, and orchards with various crops. A total of 54 species were recorded from the sampling plots and random observations, of which only 20 overlapped with Stoliczka's list; 34 were new records for Penang Hill, and 12 previously recorded species were not found in this study. Most of the new records were micro-snails smaller than 5 mm. Species richness was highest in disturbed forests and showed no correlation with elevation. There was no clear grouping of plots by species composition across habitat types, except for those in orchards. Indicator species analysis revealed strong associations between a few land snail species and disturbed forests and orchards. The number of species in Penang Hill increased from 32 to 66, with species richness comparable to the high numbers usually found in limestone habitats and higher mountains in Malaysia.

The study area locates in the east of Iran and it is morphologic block (unit). Problem statement: Sharp contrasts in the appearances of landscapes such as drainage basins with litology (kind of rock), tectonic regime, folding and climatic effect had been inspired geomorphologies in the past and now to devise schemes to explain those contrasts. These contrasts also remained and needed to research on it locally. This problem had been explained about landscape of Lut drainage basins. So, the main problem (question) is that what entity does (nature) Lut drainage basins had in comparison with tectonic lines. The Lut geomorphologic landscape is a remarkable laboratory for the examination of early and secondly geomorphic landscape, especially drainage pattern and morpho-tectonic. Approach: Due to being the arid climatic conditions of this region now, drainage development was very little. So, there was not much information about changing drainage basin in comparison with tectonic lines. Achieving to this porous in addition to some local evidence, was using 1956 aerial photograph and TM 1998 and 2002 satellite images as well as photography and geology maps, as well as indexes of drainage density, basin area, stream length, regulation circle and river gradient, were using for drainage basins and for tectonic forms using from sinuosity index of rivers and fault and others efforts. Results: Results of this study showed that drainage basin in comparison with tectonic forms with the most frequency (inter of basins) had cut the faults and streams could cut the Lut tectonic system. Sinuosity of rivers in the Lut basins is due to morpho-tectonic effect. In the other hand territory of important Lut unit drainage basins was limited to tectonic-lines and has built the bounds of basins. So in order to, tectonic changing was new and more active than drainage network now. Conclusion: Therefore, in geomorphologic view may be refer to Lut unit as a hydro-tectonic unit.

AimWe tested the hypothesis that areas that acted as historical refugia during restrictive climate regimes currently harbour higher levels of biodiversity than areas that lacked refugia.LocationThe rain forests of Australia's Wet Tropics, the largest remaining fragments of the humid forest habitats that once covered the Australian continent.MethodsWe generated a model of climatic suitability for arachnids in the genus Austropurcellia, a group of small, dispersal‐limited mite harvestmen that are found throughout the Wet Tropics. We then projected this model onto palaeoclimate data layers from time slices going back to the Last Glacial Maximum and summed suitability over time to arrive at a measure of stability. We compared the power of metrics of present and past climatic suitability and stability to predict diversity (species richness and phylogenetic diversity) across subregions of the Wet Tropics.ResultsWe found statistically significant correlations between measures of diversity (species richness and phylogenetic diversity) and present climatic suitability, LGM climatic suitability and our stability metric across subregions of the Wet Tropics. Although stability lost predictive power when analyses were corrected for spatial autocorrelation, and present‐day mean climatic suitability lost predictive power when corrected for spatial autocorrelation under one of our geographical binning schemes, mean climatic suitability during the Last Glacial Maximum had a positive and significant relationship to both number of species and phylogenetic diversity in all analyses.Main ConclusionsOur results support a model of biodiversity preservation within historical refugia, resulting in higher present‐day diversity in refugial areas than in non‐refugial areas. Although previous studies of the Wet Tropics biota have demonstrated a relationship between habitat stability and diversity, ours is the first such study to consider phylogenetic diversity in addition to number of species.

Influence of limestone and anthropogenic activities on land snail communities in Satun Province, Thailand

Valley width is a fundamental morphologic property of rivers that plays a key role in drainage networks' hydrology, ecology, and geomorphology. In many cases, defining and measuring valley width is far from trivial. Therefore, similar to channel width, the valley width (W) is commonly approximated as a power law function of the drainage area (A) and expressed as W = kcAd. Global observations have shown that the exponent  (d) can vary widely but is typically ~0.5. However, in fluvial systems that have undergone drainage reorganization, gradual or abrupt changes in drainage areas along the valley could produce widths that are disproportionate to their drainage areas. As a result, the valley width - drainage area relationship in reorganized systems is expected to differ from undisturbed drainages that have not undergone reorganization.To test this prediction, we studied 12 valleys in the Negev desert, Israel, and classified them into three categories, based on field evidence and remote sensing data: (i) undisturbed valleys, which are minimally affected by reorganization; (ii) beheaded valleys, whose headwaters were beheaded; and (iii) reversed valleys, which have reversed their flow direction by 180 degrees while exploiting their antecedent valleys. Using a new semi-automatic tool to measure valley width on high-resolution DEMs, we calibrated the best-fit power law for each valley to explore the relationships between drainage area and valley width for each valley category.Our results show that the valley width-drainage area scaling in reorganized valleys deviated significantly from those in undisturbed valleys in our field area and global observations. The drainage area exponents (d) were lower in beheaded valleys compared to undisturbed valleys but remained positive. In contrast, reversed valleys were characterized by negative d exponents, indicating valley width decrease with increasing drainage area. For the reversed category, we also explored the independent effect of channel slope (S), where the valley width is W = kb AbSc, which resulted in negative and overall similar values of b and c.In one reversed valley section, we compared the scaling of valley versus channel width as a function of drainage area. We found that in contrast to the downstream narrowing valley, the channel width shows an opposite trend and widens downstream, suggesting that the channel has mostly adjusted to the post-reorganization drainage area distribution. The narrow reversed channel shapes the width of the formative flows, which contrasts significantly with the wide flows of the beheaded valley across the divide. This difference results in a step-change in the unit stream power between the reversed and beheaded channels, potentially leading to a "width feedback" that promotes further divide migration.Our findings can be used to identify landscapes that have been affected by recent drainage reorganization and should be taken into consideration in studies that use the relationship between valley width and drainage area for valley width predictions, stream power calculations, and landscape evolution models.

We explored patterns of land snail assemblages using 93 alluvial forest sites in six river floodplains of the Elbe drainage basin (northwestern Bohemia, Czech Republic). Differences in species richness and composition across the four floodplain forest types (i.e., alder carrs, ash-alder forests, willow-poplar softwood forests, and hardwood forests) were analysed using generalized linear models, multidimensional scaling and redundancy analysis with the Monte Carlo permutation test. The studied floodplain forest types did not differ in species richness, except for the alder carrs which were significantly poorer. The number of species expressed a significant unimodal response along with elevation and Ellenberg nutrients, and further significantly decreased towards the most humid sites. Contrary to species richness, the main forest types clearly differed based on land snail species composition, with the exception of the ash-alder and willow-poplar forest sites which became completely overlapped in the ordination space. The main changes in species composition were mostly associated with elevation and Ellenberg moisture on the first MDS axis: Ellenberg nutrients and light were fitted on the second and the third axes, respectively. These variables, along with calcium content estimated using Ellenberg indicator values for soil reaction, had significant effects on the variation and snail species composition in the final RDA model. No response of either species richness or compositional changes was found for the measured content of topsoil calcium, most likely due to the higher importance of other variables. On the basis of some recently published data we can conclude that historical development and long-term human activities on the succession of floodplain assemblages have resulted in a sharp impoverishment of strictly land snail species of several hardwood forest sites in the majority of lower river stretches. Whilst in most areas there are no exact palaeoecological data available, these historical influences were closely correlated with the site elevation in our dataset as the main difference in species composition was hard to explain solely using environmental predictors.

Because land snails inhabiting the seashore are most likely to be carried by ocean currents or by attaching to seabirds, land snail fauna on oceanic islands include species derived from the mainland ancestors inhabiting the seashore. If habitat use of the island descendants is constrained by the ecology of the mainland ancestor, the island species that moved from the coastal habitat to the inland habitat may still be restricted to relatively exposed microhabitats with high pH, calcium carbonate-rich substrates, and poor litter cover. We tested this hypothesis by investigating the association between environmental conditions and species diversity of seashore-derived species of the endemic land snails on the oceanic Hahajima Island (Ogasawara Islands). Seashore-derived species showed higher species richness on limestone outcrops than non-limestone areas, whereas the other species showed no significant increase in species richness in limestone outcrops. There was a higher proportion of seashore-derived species on the limestone ridges than on the soil of dolines, even in the limestone area. Accordingly, the species derived from the seashore of the mainland are restricted to microhabitats with poor vegetation cover, poor litter cover, high pH, and calcium carbonate-rich substrates, which supports the hypothesis that the inland species on an island derived from the mainland seashore still prefer environments similar to the seashore. In addition, the seashore-derived species on the limestone outcrop include cave-dwellers lacking functional eyes. This suggests that the probability of colonizing a cave environment is restricted to seashore-derived species. The findings obtained in the present study suggest that habitat use of the ancestral lineages can constrain habitat use of the descendants, even in the oceanic islands with depauperate fauna. This bias in the species composition on the limestone outcrop constrains lineages that can colonize and adapt to the inside of caves, and therefore, habitat use of the ancestral lineages affects the ability of descendant lineages to colonize novel habitats. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102, 686–693.

Aim We investigated the patterns of species richness in land snails and slugs along a tropical elevational gradient and whether these patterns correlate with area, elevation, geographic constraints, and productivity. We did so both at the scale at which land snail population processes take place and at the coarser scale of elevational zones.Location Mount Kinabalu (4096 m) and the adjacent Mount Tambuyukon (2588 m) in Kinabalu Park, Sabah, Malaysian Borneo.Methods We used an effort‐controlled sampling protocol to determine land snail and slug species richness in 142 plots of 0.04 ha at elevations ranging from 570 to 4096 m. Extents of elevational ranges were determined by interpolation, extended where appropriate at the lower end with data from lowlands outside the study area. We used regression analysis to study the relationships between species density and richness on the one hand and elevation and area on the other. This was done for point data as well as for data combined into 300‐m elevational intervals.Results Species density (based on the individual samples) showed a decline with elevation. Elevational range length profiles revealed that range lengths are reduced at greater elevations and that a Rapoport effect is absent. Diversity showed a mild mid‐domain effect on Kinabalu, but not on Tambuyukon. When the data were combined into 300‐m elevational intervals, richness correlated more strongly with elevation than with area. Ecomorphospace was seen to shrink with increasing elevation.Main conclusions The elevational species richness patterns show the combined effects of (1) reduced niche diversity at elevations with lower productivity and (2) historical events in which the upward migration of lowland species as well as the speciation of highland endemics took place.

Aim Species richness is an important feature of communities that varies along elevational gradients. Different patterns of distribution have been described in the literature for various taxonomic groups. This study aims to distinguish between species density and species richness and to describe, for land snails in south‐eastern France, the altitudinal patterns of both at different spatial scales.Location The study was conducted on five calcareous mountains in south‐eastern France (Etoile, Sainte Baume, Sainte Victoire, Ventoux and Queyras).Methods Stratified sampling according to vegetation and altitude was undertaken on five mountains, forming a composite altitudinal gradient ranging from 100 to 3100 m. Visual searching and analysis of turf samples were undertaken to collect land snail species. Species density is defined as the number of species found within quadrats of 25 m2. Species richness is defined as the number of species found within an elevation zone. Different methods involving accumulation curves are used to describe the patterns in species richness. Elevation zones of different sizes are studied.Results Eighty‐seven species of land snails were recovered from 209 samples analysed during this study. Land snail species density, which can vary between 29 and 1 species per 25 m2, decreases logarithmically with increasing altitude along the full gradient. However, on each mountain separately, only a linear decrease is observable. The climatic altitudinal gradient can explain a large part of this pattern, but the great variability suggests that other factors, such as heterogeneity of ground cover, also exert an influence on species density. The altitudinal pattern of species richness varies depending on the spatial resolution of the study. At fine resolution (altitudinal zones of 100 m) land snail species richness forms a plateau at altitudes below 1000 m, before decreasing with increasing altitude. At coarse resolution (altitudinal zones of 500 and 1000 m) the relationship becomes linear.Main conclusions This study reveals that land snail species density and land snail species richness form two different altitudinal patterns. Species density exhibits strong variability between sites of comparable altitude. A large number of samples seem necessary to study altitudinal patterns of species density. Species density decreases logarithmically with increasing altitude. Above a critical altitudinal threshold, this decrease lessens below the rate seen in the first 1500 m. Different methods exist to scale‐up species density to species richness but these often produce different patterns. In this study, the use of accumulation curves has yielded a pattern of species richness showing a plateau at low altitude, whereas simple plotting of known altitudinal ranges from single mountains would have produced stronger mid‐altitudinal peaks. This study shows that not only factors such as temperatures and habitat heterogeneity, but also an ecotone effect, are responsible for the observed patterns.

We found a significant and positive relationship between fish species richness and four measures of stream size (drainage area, stream order, link magnitude, and downstream link) in three Illinois drainage basins. Downstream link (incorporating both stream size and size of stream at the next downstream confluence) explained the greatest portion of the variance. This suggests that downstream processes significantly influence the structure of fish communities inhabiting warmwater streams. Significantly higher numbers of fish species were collected from tributary streams (< 259 km2 drainage area) located lower in a drainage network and connected to a main channel system than from similarly sized streams located in the headwaters of a drainage network. The difference in species richness among station treatments was not due to a difference in the number of individuals collected among treatments. We were unable to accept or reject the hypothesis that differences in fish species richness were due to differences in physical habitat. The immigration–extinction hypothesis appears to provide a plausible explanation for the observed pattern in fish community structure within a drainage. The location of a stream channel within a network may provide a general template for fish community structure in warmwater drainages by regulating potential species richness.

The land snails and slugs have the highest level of endemism among all major animal groups on the California Channel Islands, with nearly 75% of the native terrestrial species confined to one or more of the 8 islands. In spite of this endemism, and in spite of the rarity of some species, the snails and slugs are one of the most poorly known groups. We present the first comprehensive overview of the land mollusk fauna of the Channel Islands, along with the results of recent intensive inventory studies. Surveys on San Clemente Island have increased the number of land mollusk species known from that island by 50%, and a single survey trip to Santa Rosa Island more than doubled the number of species known on that island. More additions to the land snail and slug fauna are certain for the poorly surveyed northern Channel Islands. This new information has provided insight into trends in species diversity and biogeographic patterns, with marked differences in species composition between the northern and southern islands. Our surveys to date suggest a strong link between the recovery of native vegetation on the islands and the population status of land snails and slugs, with substantially larger numbers of native mollusks on those islands that have been free of nonnative mammals the longest. Survey work is continuing, but it is clear that some very rare endemic snails and slugs on the islands merit specific management attention.

Aim To test the performance of the choros model in an archipelago using two measures of environmental heterogeneity. The choros model is a simple, easy‐to‐use mathematical relationship which approaches species richness as a combined function of area and environmental heterogeneity.Location The archipelago of Skyros in the central Aegean Sea (Greece).Methods We surveyed land snails on 12 islands of the archipelago. We informed the choros model with habitat data based on natural history information from the land snail species assemblage. We contrast this with habitat information taken from traditional vegetation classification to study the behaviour of choros with different measures of environmental heterogeneity. R2 values and Akaike's information criterion (AIC) were used to compare the choros model and the Arrhenius species–area model. Path analysis was used to evaluate the variance in species richness explained by area and habitat diversity.Results Forty‐two land snail species were recorded, living in 33 different habitat types. The choros model with habitat types had more explanatory power than the classic species–area model and the choros model using vegetation types. This was true for all islands of the archipelago, as well as for the small islands alone. Combined effects of area and habitat diversity primarily explain species richness in the archipelago, but there is a decline when only small islands are considered. The effects of area are very low both for all the islands of the archipelago, and for the small islands alone. The variance explained by habitat diversity is low for the island group as a whole, but significantly increases for the small islands.Main conclusions The choros model is effective in describing species‐richness patterns of land snails in the Skyros Archipelago, incorporating ecologically relevant information on habitat occupancy and area. The choros model is more effective in explaining richness patterns on small islands. When using traditional vegetation types, the choros model performs worse than the classic species–area relationship, indicating that use of proxies for habitat diversity may be problematic. The slopes for choros and Arrhenius models both assert that, for land snails, the Skyros Archipelago is a portion of a larger biogeographical province. The choros model, informed by ecologically relevant habitat measures, in conjunction with path analysis points to the importance of habitat diversity in island species richness.

There has been strong recent interest in the “macroecological” approach of explaining local community phenomena as a consequence of patterns at larger geographic scales. Various authors have suggested that if local observations can be explained by the larger-scale patterns in which they are embedded, there is less need to invoke local (within-site) processes (like competition, habitat structure, etc.) to explain community structure. We used a large database on local stream fish assemblages and species distributions in the Interior Highlands of Arkansas to test three macroecological hypotheses: (1) faunal similarities among upland river basins can be predicted from the hierarchical geographical connectivities of those streams in the larger Mississippi River Basin drainage network; (2) faunal richness of drainages up to the size of small rivers (ca. 4000 km2) increases with drainage area; and (3) local (within-site) species richness increases in proportion to regional (basin) richness. These hypotheses were tested at the level of “all species”, and within the families Cyprinidae (minnows) and Percidae (darters). For the first hypothesis, Mantel tests comparing matrices of faunal similarities and basin connectivity (based on number of nodes separating these smaller basins within the Mississippi River Basin) showed that similarities in composition of fish faunas among the upland basins were predictable from the pattern of drainage connectivity. This pattern existed at the levels of “all species”, minnows, and darters. Upland basins separated by the fewest nodes had fish faunas that were most similar, with all basins in the more northern White-Arkansas river basin separating (across all taxa and within families) from the southern Ouachita river basin drainages; and lesser rivers within these basins also showed similarity generally related to their connectivity. In tests of the second hypothesis, drainages up to small rivers in size exhibited positive, species-areas slopes at all taxonomic levels. Species-area regression slopes (z) were 0.30 for “all species”, and 0.36 for darters, both differing significantly from a slope of zero. However, minnows had a species-area regression slope of z = 0.20, which did not differ statistically (P = 0.16) from a slope of zero. For the third hypothesis, regional (basin) species richness explained little of the variation in species richness at individual local sites, with the relationship significant at P = 0.054 for mean local number of “all species”, and nonsignificant within the minnow and darter families. Within all levels of regional (basin) species richness, there was great variation in number of species found at individual sites. Overall, we conclude that extrinsic macroecological hypotheses, based on patterns at large spatial scales, differed in explaining composition of the faunas or assemblages at smaller spatial scales, leaving much variation in local assemblage structure to be explained by local intrinsic factors.

Aim We investigated whether the biogeographical patterns expected if the East African fauna was affected by cycles of contraction to refugia and expansion of ranges, as has been previously hypothesized, can be found in the land snail fauna of rain forests in Uganda.Location The Albertine Rift region and the Lake Victoria forest belt in Uganda.Methods Snails and slugs were sampled in 60 plots in 13 rain forests, and small species were extracted from 5‐L leaf litter samples. Relative species richness was calculated by rarefaction. The influence of putative determinants of species richness was examined by bivariate correlation and multiple regression. Clustering and nestedness were tested by Monte Carlo simulations with a null model that considers the range size distribution, the species richness distribution of the forests, and the spatial autocorrelation of the occurrences of each species. Biotic elements were determined by model‐based Gaussian clustering.Results A total of 169 land snail species were recorded from 13 Ugandan rain forests. Relative species richness increases with rainfall and altitude, and decreases with evaporation and distance from the putative East Congolian refugia. Mean annual rainfall and distance from the putative East Congolian refugia were included in the best multiple regression model. The distribution areas of the Ugandan land snails are significantly clustered. Two montane, two lowland and a northern biotic element were found. The mean range extension increases with increasing distance from the putative East Congolian refugia. Moreover, the ranges of the Ugandan land snails are significantly nested. The centre of the sets of nested subsets is in the Virunga Mountains, close to the putative East Congolian refugia.Main conclusions The decrease of diversity with increasing distance from the putative East Congolian refugia, the clustering and nestedness of ranges, and the range size increase with increasing distance from the refugia indicate that the East African land snail fauna was affected by cycles of contraction to refugia and expansion of ranges. The significant clustering and nestedness cannot be explained by current environmental conditions. Given the environmental history, it can be supposed that the lowland elements expanded post‐glacially, whereas the ranges of the montane species are probably currently contracting.