Snail Species Richness Research Articles

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

Southeast Asia is renowned for its rich biodiversity and serves as a global hotspot for organisms. Satun Province, located in southern Thailand, represents a significant biogeographic and biodiversity region situated in the transition zone between the Indochinese and Sundaland hotspots. Thus, Satun Province has high diversity and abundance of organisms, especially land snails. However, Satun Province has been largely understudied for both diversity and biogeography. Our study aimed to investigate land snail communities, emphasizing comparisons between the mainland and island sites, and the influence of limestone and other rock types in Satun Province. Our exploration efforts identified a diverse land snail community comprising 17 families, which updated the total reported species in the province from 22 to 58 species. The results showed that islands had significantly greater land snail species richness and abundance, and larger Shannon index values in comparison to the mainland. Anthropogenic activities on the mainland led to habitat transformation and had detrimental impacts on native land snail diversity while promoting the spread of invasive species. In contrast, the presence of little-disturbed limestone habitats on some of the islands contributed to higher richness of land snails, as limestone areas are known for their high diversity and endemism. Snail communities varied along site characteristics; especially, limestone versus non-limestone areas and human activity levels (which were associated with national park protection), with limestone and protected areas having the highest diversity. Our study illustrates the value of protected areas as potential hotspots of biodiversity, especially for islands that are little disturbed by human activities and that have habitats that support high diversity, such as limestone outcrops. This study provides valuable insights into the biogeography of land snails in Satun Province and Southeast Asia and contributes to our understanding of the factors influencing land snail diversity.

Diversity and species richness of land snails inhabiting an impacted macro-zone-Mfamosing limestone hill in Sub-Saharan Region

The land snail diversity and abundance and some ecological aspects of the fauna in a threatened limestone hill in Mfamosing, Cross Rivers state, Nigeria was investigated between May 2017 and June 2018. Twelve plots of 10 m x 10 m each using a combination of leaf litter in the forest floor (litter and topsoil in a total of ninety sample bags) were sampled from which shells were extracted by handpicking. A total of 289 (two hundred and eighty-nine) specimens representing twenty-three species in seven molluscan families were recorded. The carnivorous Streptaxidae family dominated the fauna regarding species richness while the family Urocyclidae dominated species abundance. The families Eucolinidae and Aillyidae accounted for the least dominant species. The family Streptaxidae with seven species accounted for over 30% of the mollusk abundance, while Urocyclidae had the highest number of individual specimens. True estimates of diversity using Chao2 and second-order Jack-Knife estimators yielded 25 and 24 species respectively. The Land Snail diversity in Mfamosing limestone hill when compared with those from other parts of Nigeria (Okomu in Edo State) and some other parts of the world (Sabah, Malaysia) is relatively high, with moderate levels of species abundance, showing relatively high differentiation, local dominance and endemism by few species. This reveals that Mfamosing limestone hill is one of the biodiversity hotspots for terrestrial mollusks and requires urgent conservation measures, given the current rate of Limestone quarrying in the region.

Taxonomic and functional diversity of land snails reflects habitat complexity in riparian forests

Habitat complexity affects the structure and dynamics of ecological communities, more often with increased complexity leading to greater species diversity and abundance. Among the terrestrial invertebrate groups, the low vagility of land snails makes them susceptible to react to small-scale habitat alteration. In the current paper we aimed to assess the relationship between taxonomic and functional composition and diversity of land snail communities and habitat structure in the riparian forest habitat. We found that both snail abundance and species richness responded positively to the increase in habitat complexity. The complexity of the riparian forest affected also the snail trait composition. Forest species, species living in woody debris, leaf litter, and root zone and those feeding on detritus were more abundant in complex habitats, while large snails with more offspring, snails having the ability to survive longer periods of dryness, as well as species that prefer arid habitats, were more abundant in less complex habitats. We concluded that habitat complexity promoted functional diversity, with the amount of woody debris as main positive driver, and the adjacent agricultural fields as negative driver of functional diversity.

Exploring land snails’ response to habitat characteristics and their potential as bioindicators of riparian forest quality

Riparian ecosystems are crucial for landscape-level biodiversity, especially in highly anthropic and agricultural areas. Although the low mobility of snails reduces their dispersal capacity and makes them vulnerable to habitat degradation, they are less commonly used as indicators. We evaluated the potential of land snails as bioindicators of riparian forest quality in central European riparian forests by surveying snail communities in relation to habitat characteristics that characterize its quality. Habitat characteristics were found to affect both snail abundance and species richness. The abundance of snail species increased with the forest continuity, forest width and abundance of leaf litter and decreased with the cover of ruderal plant species and presence of household waste deposits. Snail diversity was positively influenced by habitat continuity, forest width, and abundance of dead wood. The community composition was also sensitive to habitat characteristics, most species having their optimum in habitats with high amounts of decaying dead wood and litter. Many species responded positively to habitat continuity, demonstrating that fragmentation is the main factor affecting abundance of land snail communities. Both total abundance of land snail communities and species richness were good predictors of habitat quality, snail abundance being more powerful than diversity. Aegopinella epipedostoma, Perforatella bidentata, and Helix pomatia were best at discriminating among high and poor quality forest habitats among individual species. Our study showed that among the parameters describing habitat quality, spatial and temporal continuity of riparian forest are the main factors affecting snail communities. Habitat fragmentation and the absence of suitable microhabitats for snail species preferring decaying wood lead to lower abundance and diversity of land snail communities confirming the potential of land snails as bioindicators of riparian forest quality.

Assessment of snail communities in fragmented habitats

Forest fragmentation is an increasing commonality with the continued rise in disturbances from extractive industries and various anthropogenic activities. While research has observed negative effects of fragmentation such as ecotones, the impact on specific organisms is unknown. Sites were selected in three forests that have been fragmented by power lines, three forests fragmented by pipelines, and three primarily undisturbed forests to assess snail communities. Beginning at the edge of the disturbance, every 25, 50, 75, and 100m into the forest, two 1m2 quadrats were sampled on each side. Environmental data was collected along with snails visible to the naked eye; leaf litter was placed in bags and sieved for microsnails. Abundance and species richness were highest among the control sites, followed by power line rights-of-way. Since power lines have been around longer than pipelines, hypotheses conclude that snail communities need substantial time to repopulate fragmented forests. Species richness may never completely recover due to generalist and/or invasive species overtaking and outcompeting native species in these disturbed habitats. Surprisingly, environmental factors such as vegetation heterogeneity, soil temperature, and canopy cover showed no significant correlations with snail abundance or species richness. Besides site type, the driving force behind snail abundance and species richness appears to be distance from disturbance. Species richness significantly increased with distance from the disturbance. While abundance was not significant given distance from the disturbance, there was a clear observable trend. More sites should be sampled in the future as trends may likely display significance with more available data.

Species Richness and Diversity of Land Snails in Ngel-Nyaki Forest Reserve, Mambilla Plateau, Taraba State Nigeria

Species Richness and Diversity of Land Snails in Ngel-Nyaki Forest Reserve, Mambilla Plateau, Taraba State Nigeria

TERRESTRIAL SNAIL COMMUNITIES OF THE LOWER RIO GRANDE VALLEY ARE AFFECTED BY HUMAN DISTURBANCE AND CORRELATE WITH VEGETATION COMMUNITY COMPOSITION

The lower Rio Grande Valley of Texas (LRGV) contains a unique, subtropical, semiarid floodplain with most of the few remaining Tamaulipan thorn forests in the United States. Less than 2% of Tamaulipan thorn forest remains, with urban and agricultural conversion potentially threatening diverse plant and animal communities native to the habitat. We performed vegetative community surveys and conducted a comprehensive survey of terrestrial snail communities in intact (refugia sites, minimally altered in recent times) and altered (previously cleared and regrown or restored) Tamaulipan thorn forest habitats of the LRGV. In a comparison of intact and altered sites that have comparable vegetation (paired sites), we found that intact sites had a less species-rich snail community than their altered counterparts, but this difference was not statistically significant. This counterintuitive result, in part reflects the fact that the most species-rich, intact snail communities (i.e., Sabal Palm Forest) have no altered (restored or regrown) counterparts and so were not included in the paired comparisons. A nestedness analysis supports this, finding that these unique intact sites, which have the highest species richness and no comparable restored sites, contain the largest pool of species in South Texas. Species richness of snails significantly correlated with a precipitation gradient. A general linear model incorporating mean canopy cover, mean plant height, plant abundance, and plant species richness shows a significant correlation with snail communities. This study is the only comprehensive survey of the snail communities of the lower Rio Grande Valley.

Land snail from limestone karst in Java: an update with notes on their distribution

Limestone karst in Java is rich of land snail fauna. Unfortunately, the ecosystem is now threatened by mining or tourism activities. However, the impact of that activities on land snail diversity is not well studied. The objective of this study was to inventory the diversity of land snail in limestone karst with focus on their ecological and distribution in Java. Purposive sampling methods using plots (10 x 10 m) were used in 12 different stations in Western Java, Central Java, and Yogyakarta during 2017-2018. Thirty-five species from eleven families of land snail were identified. The highest species richness and population of land snails were found in Watu Blencong (16 species and 158 individuals). Landouria rotatoria distributed in eight locations, while Japonia ciliocinctum (85 individuals) distributed in six locations. Results showed that extended distribution records of ten land snail species were reported. Currently, 63 species of land snails species have been identified in karst ecosystem in Java.

Parasite diversity and ecology in a model species, the guppy (Poecilia reticulata) in Trinidad.

The guppy (Poecilia reticulata) is a model species in ecology and evolution. Many studies have examined effects of predators on guppy behaviour, reproduction, survival strategies, feeding and other life-history traits, but few have studied variation in their parasite diversity. We surveyed parasites of 18 Trinidadian populations of guppy, to provide insight on the geographical mosaic of parasite variability, which may act as a source of natural selection acting on guppies. We found 21 parasite species, including five new records for Trinidad. Spatial variation in parasite diversity was significantly higher than that of piscine predators, and significant variation in parasite richness among individuals and populations was correlated with: (i) host size, (ii) snail species richness, and (iii) the distance between populations. Differences in parasite species richness are likely to play an important, yet underestimated role in the biology of this model species of vertebrate ecology and evolution.

Land snail dispersal, abundance and diversity on green roofs.

We present the first major systematic study of land snail diversity on green roofs. We surveyed 27 green roofs and the adjacent ground habitat in six major cities in the southeastern United States. We found a total of 18 species of land snails, with three considered to be non-native or invasive species. The majority of land snails encountered in surveys are widespread, generalist species, typically adapted to open habitats. Twelve of the land snails encountered are “greenhouse” species that are very commonly transported via the horticultural trade. Therefore, we infer that at least some land snail species are introduced to green roofs via initial green roof installation and associated landscaping. The major determinants of snail species richness and abundance are the size of each roof and the quality of green roof maintenance regime.

Does forest age affect soil biodiversity? Case study of land snails in Mediterranean secondary forests

Based on a sampling design used for vascular plants, the effect of forest age (i.e. the time in years since a land patch became a real forest patch as a measure of temporal continuity of forest characteristics) on land snail richness, abundance and composition was assessed in 18 plots in Mediterranean evergreen and deciduous oak forests, belonging to four Sites of Community Importance in Italy. Most examined plots belong to young forests; in particular, three age classes were considered (class 1, <22 years; class 3, 38–56 years; class 5, >77 years). Twenty-seven species and 2433 individuals were recorded. Box plots showed that forest age did not seem to be a key factor for land snail species richness and abundance at least in the time range of examined forests. However, this may not be true, if real old-growth forests are considered. No differences between evergreen and deciduous forest were found too. With regard to species composition, Non-metric multidimensional scaling demonstrated an assemblage of species widespread in all forest age classes, while Indicator Species Analysis failed to identify any species as indicator for any age category. This shows that a process is underway but has had insufficient time to differentiate assemblages and to accumulate the majority of rare species, due to the young nature of examined forests. Habitat structure may affect communities more than forest age: suitable microhabitats (a few old/very old trees for shelter) are a sufficient prerequisite for land snail diversity, ensuring community survival and protection, irrespective of forest age class. These findings highlight the importance of habitat structural complexity at local scale for preserving invertebrate diversity in Mediterranean secondary forests.

Retention trees can benefit biodiversity without significant long-term reduction in stand regeneration in Estonian mixed forests

Retention forestry is regarded as an efficient approach for conserving ecosystem functions and biodiversity in production forests, but its long-term impacts on forest ecosystem goods and services are poorly documented. We investigated the functioning of solitary retention trees in regenerated young forest as refuges or dispersal centres for shade-preferring species and explored the potential cost on future timber supply due to suppressed tree regeneration. We described land snail assemblages, soil characteristics, vegetation structure and stand regeneration along 50-m transects radially away from 34 deciduous retention trees in young stands (15–16 years post-harvest, passed the pre-commercial thinning) in Estonia. General linear modelling revealed that the abundance and species richness of snails were higher in close proximity of the retention trees. Neither stand regeneration density nor its basal area varied systematically along the distance gradient. Thus, contrary to our hypothesis, the positive impact of retention trees on shade-preferring and hygrophilous species group in young production stands had no clear trade-off with stand regeneration. The development of both these functions should be studied further in maturing forests.

Global species richness of hydrobiid snails determined by climate and evolutionary history

Abstract Efforts to describe spatial patterns of freshwater diversity and to evaluate their underlying factors have traditionally been focused on some animal groups (e.g. amphibians, fish or dragonflies). Despite being a dominant component in continental aquatic ecosystems and crucial for determining priority areas for conservation, broad‐scale data on gastropod total species, endemic and threatened species richness are limited. Based on these biodiversity indices, we identify global hotspots, extinction risk along the elevational gradient and the drivers of species richness patterns in the largest group of freshwater gastropods, the family Hydrobiidae. Given the strong dependency to a nonmarine aquatic environment, the observed richness patterns of extant hydrobiid species could be significantly influenced by large‐scale geography and dispersal processes as well as climatic conditions affecting continental ecosystems. Therefore, we tested several predictions for species richness derived from ecological and evolutionary hypotheses postulated for other freshwater groups. Based on a comprehensive literature and biodiversity database review, we compiled the number of total, endemic and threatened species per freshwater ecoregion. We classified ecoregions as hotspots if each biodiversity index was in the top 25% of its range and assessed the effect of 13 environmental and evolutionary factors on species richness using generalised linear models. We identified 906 species and 157 genera of Hydrobiidae showing mainly a Nearctic–Palearctic distribution and 19 biodiversity hotspots, most located across the Mediterranean Basin. In our data set, 83% of the species were endemic to a single ecoregion. Of the 43% non‐data deficient species, we found almost three times more threatened than non‐threatened species, and extinction risk peaked at 1,500 m a.s.l. Species richness was unequally distributed over biogeographic realms, increased with higher connectivity among ecoregions, and was negatively related with annual temperature range. Latitude and precipitation seasonality explained part of the richness variation by a nonlinear relationship. The identified hotspots correspond with those of other freshwater taxa. The hump‐shaped relationship of extinction risk with elevation is likely the consequence of decreasing natural and anthropogenic perturbations at higher elevations. Global hotspots of Hydrobiidae richness represent areas of climatic stability with medium precipitation and temperature seasonality that are well connected with other hydrological basins. Our results illustrate that both evolutionary and environmental factors determine these global patterns and that future changes of the latter factors may affect hydrobiid richness.

Intensity-dependent impact of sport climbing on vascular plants and land snails on limestone cliffs

Limestone cliffs in the Jura Mountains harbour species-rich plant and animal communities including rare species. Sport climbing has recently increased in popularity in this habitat and several studies have reported damage to cliff biodiversity. However, so far how damage levels vary with climbing intensity has not been investigated. We evaluated the effects of climbing intensity on the diversity of vascular plants and land snails in 35 limestone cliff sectors in the Northern Swiss Jura Mountains. Mixed-effects models were used to examine whether species richness of plants and land snails differ between cliff sectors with low and high climbing intensity and unclimbed cliff sectors (controls) taking into account potential influences of cliff characteristics (aspect, cliff height, rock microtopography). At the cliff base, the best fit model revealed that plant species richness was affected by climbing intensity and cliff aspect. Plant species richness was reduced by 12.2% and 13.1%, respectively, in cliff sectors with low and high climbing intensity compared to unclimbed cliff sectors. On the cliff face, plant species richness was only influenced by climbing intensity (species richness reduction by 24.3% and 28.1%). Combining data from cliff base, face and plateau, the best fit model revealed that land snail species richness was only affected by climbing intensity (species richness reduction by 2.0% and 13.7%). In both organism groups, species composition was increasingly altered by increasing climbing intensity. Our study provides evidence that even low climbing intensity reduces cliff biodiversity and that damage becomes more pronounced with increasing climbing intensity.

Terrestrial Gastropods: Survey and Relationships between Land Snail Assemblage and Soil Properties

Terrestrial gastropods (snail and slug) species were studied concerning their occurrence survey and population density in 25 localities representing five districts of Kafr EL-Sheikh Governorate, during September 2015 to August 2016. An attempts to obtain basic information concerning their relationships between land snail species assemblage and soil properties .Ten herbivorous species, eight land snails and two land slugs' species belonging to three families Helicidae, Succinidae, Limacidae of order Stylomatophora were found on different crops. Population density of Land snails and slug species varied in their incidence and level of infestation according to each locality and host type. Soil samples were taken from five districts due to analytical chemically and assess the relationships between low or high snail population density and soil component. There is positive relation between terrestrial gastropods population and soil calcium content. Organic matter, soil PH and salinity (EC, electric conductivity) with low and high density in all districts were average [(1.2 and 2.9), (7.54 and 9.01) and (1.54 and 4.52)] respectively. It is clearly that Organic matter, soil PH and EC had negative correlation with land gastropods low or high densities. However, the quantitative species composition of the land snail assemblage is related to soil properties to a lower degree than snail density and species richness, and other habitat characteristics such as vegetation can be important for species abundance.

Acidic, neutral and alkaline forest ponds as a landscape element affecting the biodiversity of freshwater snails

In recent years, the number of areas remaining under the influence of acidity has increased. At all levels of ecosystems, biodiversity decreases with acidification, due to the elimination of species that are most sensitive to low pH. Forest ponds belong to a specific group that varied in location, a huge amount of leaf litter, and isolation from other aquatic environments. They are crucial in the industrial landscape with well-developed industry and human activity. The aim was to investigate the relative importance of water chemistry in explaining snail assemblage compositions and species richness in forest ponds of contrasting pH. Patterns in gastropod communities were determined from an analysis in 26 forest ponds with multivariate gradient analysis. Ponds ranged in a base mean pH from 3.0 to 9.0. pH has been found to be an important factor influencing gastropod fauna. Neutral ponds support diverse communities, typical of small water bodies. In two acidic pond types, snail fauna was different. Among the species characteristic for acidic ponds (pH < 6) were Anisus spirorbis and Aplexa hypnorum. The greatest distinct characterised alkaline ponds with the numerous appearance of alien Physa acuta. The most diverse gastropod fauna was found in neutral ponds, whereas the lowest degree of diversity was found in ponds with the lowest pH. Current knowledge of pH-associated changes in aquatic ecosystems is still incomplete because anthropogenic acidification is a recent phenomenon. It is extremely important in forest habitats, since they react more intensively to climatic factors and are often used in landscape management and planning.

Associations between patterns of human intestinal schistosomiasis and snail and mammal species richness in Uganda: can we detect a decoy effect?

In recent years, ecological research has suggested several mechanisms by which biodiversity might affect the risk of acquiring infectious diseases (i.e., the decoy, dilution or amplification effects), but the topic remains controversial. While many experimental studies suggest a negative relationship between biodiversity and disease, this relationship is inherently complex, and might be negative, positive or neutral depending on the geographical scale and ecological context. Here, applying a macroecological approach, we look for associations between diversity and disease by comparing the distribution of human schistosomiasis and biogeographical patterns of freshwater snail and mammal species richness in Uganda. We found that the association between estimated snail richness and human infection was best described by a negative correlation in non-spatial bi- and multivariate logistic mixed effect models. However, this association lost significance after the inclusion of a spatial component in a full geostatistical model, highlighting the importance of accounting for spatial correlation to obtain more precise parameter estimates. Furthermore, we found no significant relationships between mammal richness and schistosomiasis risk. We discuss the limitations of the data and methods used to test the decoy hypothesis for schistosomiasis, and highlight key future research directions that can facilitate more powerful tests of the decoy effect in snail-borne infections, at geographical scales that are relevant for public health and conservation.

Effect of soil conditions and landscape factors on macro-snail communities in newly created grasslands of restored landfill sites in the UK

Though restored landfill sites provide habitat for a number of taxa, their potential for land snail remains unexplored. In this study, large-sized land snails (> 5 mm) were surveyed using transect sampling on nine restored landfill sites and nine corresponding nature sites in the East Midlands region of the UK during 2008. The effect of restoration was investigated by examining land snail species composition, richness, and diversity (Shannon Weiner index) in relation to habitat and landscape structure. Thirteen macro-snail species were found in total and rarefied species richness and diversity on restored landfill sites was not found to be statistically different to that of reference sites. One third of the snail species, comprising 30% of total abundance, found in the restored landfill sites were non-native species introduced to the UK. Soil electrical conductivity was the strongest predictor for richness and diversity of land snails. Road density was found to have a positive influence on snail species diversity. Given the high percentage of introduced species detected further research is needed in terms of the management implications of restored landfill sites and the dynamics of native versus non-native species.

Diversity, habitats and size-frequency distribution of the gastropod genus Conus at Dahab in the Gulf of Aqaba, Northern Red Sea

Topographically complex subtidal reefs of the Indo-West Pacific region are characterised by a high species richness of cone snails of the genus Conus (up to 36 on some reefs) but low population densities (≤1 individual/m2), whereas Conus assemblages on reef flats usually support fewer species (5–9) and high population densities (up to 5.2 individuals/m2). Subtidal sand areas are known to be least species-rich (1–6 species). Although the diversity of this predatory gastropod genus has been described previously from different areas of the Indo-Pacific, little ecological information is available on Conus in the Northern Red Sea. Therefore, data from five habitat types were obtained along 73 line-transects (245 m2), which yielded ecological data for a total of 175 individuals of 9 species. In accordance with former findings, our results demonstrate that the reef flat was the habitat with the highest observed population densities (6.15 individuals/m2) but low species diversity (H’ = 0.9; 5 species); subtidal reefs, in contrast, were characterised by low densities (0.13 individuals/m2) and a relatively high species diversity (H ‘= 1.5; 6 species). This suggests that Conus diversity and species richness in the Northern Red Sea around Dahab is lower than in other parts of the Indo-West Pacific region. Furthermore, hardand soft substrata were dominated by different Conus species in accordance to the distribution of favourable microhabitat patches, the degree of physical stress and the availability of refuges and prey organisms. The fact that these Conus were predominantly small-bodied vermivores (size range: 6–85 mm; mean shell size: 15 mm; SD = 9 mm) suggests that this size class possesses an advantage over molluscivores and piscivores. Except for subtidal reefs, which showed a highly variable species composition, the studied habitat types around Dahab were characterised by distinct assemblages of Conus.

Local and regional scale biodiversity patterns of forest snail assemblages in Tuscany (central Italy)

The land mollusc faunas of three forest areas of Tuscany (central Italy) were sampled to test the effect of geographical and environmental factors on the structure of biodiversity. A total of 60 sites were surveyed in the years 2009-2011, recording species richness and abundance of snails in 400 m2 plots randomly selected in beech and oak woods. Sampling strategy relied on a combination of visual search and litter analysis. Environmental variables (topsoil pH and altitude) and UTM coordinates were recorded to detect relationships with species richness and number of individuals per plot. Abundance data were analyzed using non-metric multidimensional scaling and canonical correspondence analysis; faunal similarity within and between areas was computed by the Bray Curtis index and snail assemblages of the two forest types were compared. A total of 55 species were recorded, with low values of local richness and abundance per site compared to other forest sites in central and northern Europe. Total richness was similar in the three areas, but composition and local richness varied significantly between them. Geographical factors explained the highest percentage of variance, while habitat type, altitude and pH only accounted for a minor part. Internal similarity was greater than between-area similarity in two out of three areas. Beech forests had richer and more heterogeneous faunas, but lower levels of abundance than oak woods. The results are discussed in terms of historical biogeography and local environmental conditions, and compared with those from similar surveys across Europe.