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Strategies for Collecting Land Snails and Their Impact on Conservation Planning *
Abstract
Land snail collecting methods are each designed with a particular purpose. This paper provides a brief overview of land snail collecting strategies, suggests the use of multiple methods and collection of ecological data to broaden the knowledge of land snail life habits and relationships with their environment, and indicates approaches that are most relevant to land snail conservation.
... In general, more sites were sampled on larger islands, but at least six were sampled on each island. The methods prescribed by Cameron and Pokryszko (2005), and Coppolino (2010) were used to collect land snail specimens. Initial prospecting of sites ensured the presence of snails to maximize their abundance and richness. ...
... Initial prospecting of sites ensured the presence of snails to maximize their abundance and richness. This practice is common for collecting macrosnails and helps to compensate for their patchy distributions and improves detection of rare species (Szybiak et al. 2009;Coppolino 2010;Bros et al. 2016). Field methods were designed to maximize efficient detection of macrosnails and did not include bulk sampling of soils, which has been suggested as the most effective method for detecting microsnails (snails with shells \ 5 mm in their maximum dimension as adults) (Coppolino 2010). ...
... This practice is common for collecting macrosnails and helps to compensate for their patchy distributions and improves detection of rare species (Szybiak et al. 2009;Coppolino 2010;Bros et al. 2016). Field methods were designed to maximize efficient detection of macrosnails and did not include bulk sampling of soils, which has been suggested as the most effective method for detecting microsnails (snails with shells \ 5 mm in their maximum dimension as adults) (Coppolino 2010). Furthermore, many microsnail species are burrowing, so their presence in mostly surficial samples may have more to do with soil processes than ecology. ...
Natural areas near human-modified landscapes experience factors that may affect local biodiversity at levels commensurate with natural environmental factors. The land snails of the Canary Islands provide excellent opportunities to evaluate the importance of anthropogenic agents in mediating the diversity and distribution of species. Land snails are particularly sensitive to disturbance and are an integral part of terrestrial ecosystems. This study analyzed the distributions and abundances of terrestrial macrosnail shell assemblages at 60 localities throughout the coastal scrub biome of the Canary Islands. This was accomplished using data on natural and anthropogenic variables to assess their relative importance in governing land snail diversity. A total of 34,801 dead shells represented a diverse malacofauna with highly localized endemism. Due to uncertain species identifications, samples from the 18 sites from the two easternmost islands are described, but excluded from statistical analyses. Regression tree analysis indicated that proximity to agricultural sites was the most important predictor of species diversity. Sites with no or very little agricultural area (≤ 0.167 km²) within a 1 km radius had significantly higher richness and diversity. These results have implications for Canary Islands conservation. Protected areas that are patchworks of natural and agricultural landscapes are still subject to native biodiversity loss because of anthropogenic impacts even when the footprint of agriculture is small.
... These included populations from the University of Colorado Mountain Research Station; Jess Weaver trail and three locations along the Hanging Lake trail, all in White River National Forest; Lower Bear Trail in Routt National Forest; Steamboat Springs; and Glenwood Canyon. We used a qualitative collection method to collect specimens for this study, in accordance with Li, 2021b andCoppolino, 2010. All collections were taken with the appropriate permitting for invertebrates, along with special permissions from private landowners, the University of Colorado Mountain Research Station, White River National Forest, and Routt National Forest. ...
Animal gut microbiome is often a key requirement for host nutrition, digestion, and immunity. Gut microbiomes can shift in relation to host geography and environmental factors. However, ecological drivers of microbiome community assembly across large geographic ranges have rarely been examined in invertebrates. Oreohelix strigosa (Rocky Mountainsnail) is a widespread land snail ranging across the mountainous western United States. O. strigosa is found in a variety of environments, including dry Southwestern habitats and the near-alpine of the Rocky Mountains. It is ideally suited for biogeography studies due to its broad distribution, low migration, and low likelihood of passive transport via other animals. This study aims to uncover large-scale geographic shifts in the composition of O. strigosa gut microbiomes by utilizing samples from across its native range. Additionally, we elucidate smaller-scale microbiome variation using samples collected only across the Colorado Front Range. Our results show that O. strigosa gut microbiome is variable across the broad geographic range. Within Coloradan samples, we investigated several possible ecological drivers of the geographic variation, including soil and vegetation composition, habitat complexity, habitat type, and human impact. We conclude that several small-scale environmental factors may be driving the changes in O. strigosa gut microbiome composition seen across large-scale geography. Uncovering large-scale shifts in the gut microbiome compositions will help form fundamental questions about the functional aspect of these qualitative changes. This knowledge will also help us better understand how microbial associations influence species survival in diverse environments and aid wildlife conservation efforts.
... In the summer months of 2018 (between July and September) when terrestrial snails of the Rockies are most active, we collected fresh, living samples of Oreohelix strigosa from three locations within the Colorado Front Range: (1) (Table 1). We used a qualitative collection method, i.e., collections made by direct visual searching, to collect specimens for this study, in accordance with Chalifour & Li [13] and Coppolino [16]. All collections were taken with the appropriate permitting for invertebrates. ...
Background
Museum biological specimens provide a unique means of gathering ecological information that spans wide temporal ranges. Museum specimens can also provide information on the microbial communities that persist within the host specimen. Together, these provide researchers valuable opportunities to study long-term trends and mechanisms of microbial community change. The effects of decades-long museum preservation on host-microbial communities have not been systematically assessed. The University of Colorado’s Museum of Natural History has densely sampled Oreohelix strigosa (Rocky Mountainsnail) for the past century; many are preserved in ethanol, which provides an excellent opportunity to explore how the microbiome changes across time in preservation.
Results
We used 16S rRNA (ribosomal ribonucleic acid) gene amplicon sequencing to examine Oreohelix strigosa gut microbiomes from museum specimens across a 98-year range, as well as within short-term preservation treatments collected in 2018. Treatment groups included samples extracted fresh, without preservation; samples starved prior to extraction; and samples preserved for 1 month, 6 months, and 9 months. General microbiome composition was similar across all years. Sample groups belonging to specific years, or specific short-term treatments, showed unique associations with select bacterial taxa. Collection year was not a significant predictor of microbial richness, though unpreserved short-term treatments showed significantly higher richness than preserved treatments. While the year was a significant factor in microbiome composition, it did not explain much of the variation across samples. The location was a significant driver of community composition and explained more of the variability.
Conclusions
This study is the first to examine animal host-associated microbiome change across a period of nearly one century. Generally, geographic location was a greater factor in shaping gut microbiome composition, rather than a year collected. Consistent patterns across this temporal range indicate that historic specimens can answer many ecological questions surrounding the host-associated microbiome.
FUt4r1ybgCn9QXSuDujGb2Video Abstract
... A mosaic of soil, grass, individual plant and concrete structure constituted the habitat elements with ample moisture and shade conditions, qualifying as prospective spaces for the presence of the snails (Sturm, Pearce, and Valdes 2006). The sampling unit for the observation and recording of snail was in the form of quadrat applied for sampling of the habitats within the sites (Ludwig and Reynolds 1988;Brower et al. 1998;Krebs 1999;Coppolino 2010). An initial visual inspection was carried out for 10 minutes to record the presence of snails in a randomly chosen 10 Â 10 m 2 plot (quadrat) in the study sites. ...
Due to the minimal dispersal capabilities and dependency on particular microhabitat, the land snails are susceptible to an-thropogenic and natural disturbances. Considering the increasing anthropogenic threats, especially in urban areas, information on species' requirements for particular habitat is very essential for land snail conservation and sustenance. In the present commentary, diversity and distribution of small-sized land snails in relation to their microhabitat preference in urban habitats of Kolkata, West Bengal, had been carried out through the quadrat method. The information on the richness and abundance of snails and their habitat places in Kolkata, India, was used to construct a bipartite network. A total of 13 land snail species were linked with 16 microhabitats. The network indices were used to justify the specialist or generalist nature of the snail species in the context of microhabitat preference. The snail species Succinea daucina and Allopeas gracile were observed to be associated with the maximum number of habitats while species strength was highest for S. daucina. The low value of connectance (0.288, <0.5) and niche overlap (0.34), the high value of specialization index H 2 0 (0.58) and d 0 (0.44) indicate that the snail-microhabitat interactions were highly specialized. The network ecology of snail-microhabitats illustrated in the present instance will enable the identification of preferred microhabitats, which are required for the enhancement of the population of land snails in urban areas like Kolkata, India.
... (Table 1). We used a qualitative collection method to collect specimens for this study, in accordance with Chalifour & Li, 2021 [20] and Coppolino 2010 [23]. All collections were taken with the appropriate permitting for invertebrates. ...
Background
Oreohelix strigosa (Rocky Mountainsnail) is a land snail found in the talus slopes of the Rocky Mountains. The University of Colorado’s Museum of Natural History has densely sampled Oreohelix for the past century; many are preserved in ethanol and available for molecular research. While microbiome compositions in other systems are not affected by short-term field season preservation, the effects of decades-long preservation have yet to be assessed.
Results
We used 16S rRNA (ribosomal ribonucleic acid) gene amplicon sequencing to examine Oreohelix strigosa gut microbiomes from museum specimens across a 98-year range, as well as within short term preservation treatments collected in 2018. Treatment groups included samples extracted fresh, without preservation; samples starved prior to extraction; and samples preserved for 1 month, 6 months, and 9 months. General microbiome composition was similar across all years. Sample groups belonging to specific years, or specific short-term treatments, showed unique associations with select bacterial taxa. Collection year was not a significant predictor of microbial richness, though unpreserved short-term treatments showed significantly higher richness than preserved treatments. While year was a significant factor in microbiome composition, it did not explain much of the variation across samples. Other factors like location collected and drought index were also significant drivers of community composition and explained as much or more of the variability.
Conclusions
This study is the first to examine animal host associated microbiome change across a period of nearly one century. Generally, geographic location was a greater factor in shaping gut microbiome composition, rather than year collected. Consistent patterns across this temporal range indicate that historic specimens can answer many ecological questions surrounding the host associated microbiome.
... Regarding taxonomic biases present in the compiled dataset, there is a substantial inequality in the number of records for micro-mollusks and slugs compared to all other taxonomic subsets. These two taxonomic subsets comprised only a fraction of the total dataset (Table 1), likely owing to the lack of systematic survey efforts that include leaf-litter sampling (Coppolino 2010, Durkan et al. 2013. The paucity of slug specimens is likely due to their lack of a shell which makes properly preserving them difficult, further biasing our dataset towards land snails. ...
... O. strigosa are most likely to be found under the bark of trees (specifically preferential to aspens), near bases of rocks, under logs, and in other microhabitats that might be missed in a completely random selection of samples. Therefore, the qualitative collection approach can maximize collection success [41]. All collections were taken with the appropriate permitting for invertebrates. ...
Background
The Rocky Mountainsnail ( Oreohelix strigosa ) is a terrestrial gastropod of ecological importance in the Rocky Mountains of western United States and Canada. Across the animal kingdom, including in gastropods, gut microbiomes have profound effects on the health of the host. Current knowledge regarding snail gut microbiomes, particularly throughout various life history stages, is limited. Understanding snail gut microbiome composition and dynamics can provide an initial step toward better conservation and management of this species.
Results
In this study, we employed 16S rRNA gene amplicon sequencing to examine gut bacteria communities in wild-caught O. strigosa populations from the Front Range of Colorado. These included three treatment groups: (1) adult and (2) fetal snails, as well as (3) sub-populations of adult snails that were starved prior to ethanol fixation. Overall, O. strigosa harbors a high diversity of bacteria. We sequenced the V4 region of the 16S rRNA gene on an Illumina MiSeq and obtained 2,714,330 total reads. We identified a total of 7056 unique operational taxonomic units (OTUs) belonging to 36 phyla. The core gut microbiome of four unique OTUs accounts for roughly half of all sequencing reads returned and may aid the snails’ digestive processes. Significant differences in microbial composition, as well as richness, evenness, and Shannon Indices were found across the three treatment groups.
Conclusions
Comparisons of gut microbiomes in O. strigosa adult, fetal, and starved samples provide evidence that the host internal environments influence bacterial community compositions, and that bacteria may be transmitted vertically from parent to offspring. This work provides the first comprehensive report on the structure and membership of bacterial populations in the gastropod family Oreohelicidae and reveals similarities and differences across varying life history metrics. Strong differentiation between these life history metrics demonstrates the need for wider sampling for studies of dynamics of the snail gut microbiome.
... O. strigosa are most likely to be found under the bark of trees (speci cally preferential to aspens), near bases of rocks, under logs, and in other microhabitats that might be missed in a completely random selection of samples. Therefore, the qualitative collection approach can maximize collection success [36]. All collections were taken with the appropriate permitting for invertebrates. ...
Background
The Rocky Mountainsnail (Oreohelix strigosa) is a terrestrial gastropod of ecological importance in the Rocky Mountains of western United States and Canada. Across the animal kingdom, including in gastropods, gut microbiomes have profound effects on the health of the host. Current knowledge regarding snail gut microbiomes, particularly throughout various life history stages, is limited. Understanding snail gut microbiome composition and dynamics can provide an initial step toward better conservation and management of this species. ResultsIn this study, we employed 16S rRNA gene amplicon sequencing to examine gut bacteria communities in wild-caught O. strigosa populations from the Front Range of Colorado. These included three treatment groups: (1) adult and (2) fetal snails, as well as (3) sub-populations of adult snails that were starved prior to ethanol fixation. Overall, O. strigosa harbors a high diversity of bacteria. We sequenced the V4 region of the 16S rRNA gene on an Illumina MiSeq, and obtained 2,714,330 total reads. We identified a total of 7,056 unique operational taxonomic units (OTUs) belonging to 36 phyla. The core gut microbiome of four unique OTUs accounts for roughly half of all sequencing reads returned and may aid the snails’ digestive processes. Significant differences in microbial composition, as well as richness, evenness, and Shannon Indices were found across the three treatment groups.Conclusions
Comparisons of gut microbiomes in O. strigosa adult, fetal, and starved samples provide evidence that the host internal environments influence bacterial community compositions, and that bacteria may be transmitted vertically from parent to offspring. This work provides the first comprehensive report on the structure and membership of bacterial populations in the gastropod family Oreohelicidae and reveals similarities and differences across varying life history metrics. Strong differentiation between these life history metrics demonstrates the need for wider sampling for studies of dynamics of the snail gut microbiome.
... (2) Obtaining large samples is relatively simple due to high population densities, sometimes exceeding 5000 individuals/m 2 (Coles and Nekola 2007); in combination with the accumulation of shells for up to a decade following death (Pearce 2008). This greatly increases the encounter rate for rare and uncommon species (Rundell and Cowie 2004;Pearce 2008;Coppolino 2010). Additionally, accurate species level identification is usually possible via use of shell features alone (Nekola, Coles, and Horsá k 2015;. ...
A noted impact of urbanization is the tendency for biotic homogenization, or the increase of similarity of geographically disparate communities. On the other hand, some urban habitats harbor biodiversity native to their region, a role potentially important in xeric landscapes, with irrigation increasing the coverage and availability of mesic habitats in an otherwise water-limited landscape. We assessed the relative importance of urban yards as agents of biotic homogenization or riparian refugia by characterizing community composition of Tamaulipan thornforest land snail assemblages across a pronounced precipitation gradient in far south Texas, USA. We quantified α- and β-diversity and assessed whether the land snail fauna of urban yards are more similar to each other across a precipitation gradient than they are to their wild counterparts, as well as determined the significance of moisture in driving Tamaulipan thornforest β-diversity, both in terms of turnover (changing species composition) and nestedness (species loss). Sites with both the wild and wet conditions had the highest values of species richness and abundance. Urban land snail communities were significantly homogenized, outweighing the influence of the precipitation gradient. We did not find urban yards served as a refuge for native, moisture-dependent, riparian snails. Our analyses find that turnover, not nestedness, is the largest contributor to β-diversity in these assemblages. Studies of urbanization should address regional spatial scales to quantify how urbanization modifies regional biodiversity arising from background environmental gradients. Such an approach could lead to improved understanding of how large metroplex areas could be used to maintain and even promote biodiversity.
... dead wood, tree bark, sheltered places under stones) in order to find small and very small species (Cameron and Pokryszko, 2005). This method combined with visual search provides the most information on small land snail species (Menez, 2007;Coppolino, 2010;Benocci et al., 2015) (. The material collected was sieved in a mesh of 10 mm, then dried and finally sieved again with meshes of decreasing size down to 0.5 mm. ...
... El método de colecta empleado fue búsqueda cualitativa visual (Coppolino, 2010) directamente en los bosques y poblados aledaños a éstos, donde se reportó su hábitat. Para conocer la distribución geográfica exacta de las seis especies involucradas en el presente estudio se hizo una revisión de datos geográficos publicados con anterioridad (Bequaert, 1948;Ramírez et al., 2003;Ramírez et al., 2012), localidades de colecta detalladas en tabla 5. ...
Morphological characters have traditionally been the key to correctly classify and
identify organisms, the addition of molecular biology tools has been able to further
and more precisely define taxonomic keys. However, it has been observed that
sequence markers arrive at the limit of resolution in some groups of animals such
as the case of the land snail of genus Megalobulimus, making the molecular
characterization of its species difficult as well as the reconstruction of their
phylogenetic relationships. The importance of discriminating species of this
genus is beyond of an academic issue, but also a matter of economic-commercial
importance in Peru, as well as to the protection of its biodiversity.
A total of 69 individuals from six taxa, belonging to 12 provinces and 6 regions of
Perú were used. 13 ISSR primers were evaluated, resulting in six of them with high
levels of polymorphism (SAS 1 was the most variable). All experimental
procedures were run in duplicate with 10% of the samples, obtaining the same
results, which supports the reproducibility of the technique and reliability of the
outcomes.
In the interspecific analysis of Megalobulimus, 166 informative sites were
obtained, and the PIC (Polymorphic Information Content) values for the primers
used had a range of 0.36 to 0.46 and the Resolution Power values of the bands
(RP) ranged from 9.6 to 23.1 clearly discriminating to six species.
The species M. capillaceus and M. florezi are not discriminable with classical
sequence markers (COI, 16S rRNA), however, they showed clear differentiable
electrophoretic profiles, supported by statistical values. Likewise, M.
popelairianus sensu lato revealed two profiles, the variety 'thammianus' was unequivocally discriminated against from the species M. popelairianus. Although
Martens (1876) reported to ‘thammianus’ as a variation of the species M.
popelairianus, the differences between the ISSR profiles of these two groups are
comparable to that found among other recognized species of the genus such as
M. carrikeri and M. lichtensteini differentiable both morphologically and with
sequence markers.
... dead wood, tree bark, sheltered places under stones) in order to find small and very small species (Cameron and Pokryszko, 2005). This method combined with visual search provides the most information on small land snail species (Menez, 2007;Coppolino, 2010;Benocci et al., 2015) (. The material collected was sieved in a mesh of 10 mm, then dried and finally sieved again with meshes of decreasing size down to 0.5 mm. ...
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.
... Estudios precedentes sugieren que la combinación de varios métodos y unidades de muestreos resulta la forma más efectiva para maximizar la riqueza observada en un área. Es importante resaltar la vulnerabilidad de muchas especies de moluscos terrestres ante la pérdida de hábitat y la recolecta desmedida que conllevan a la disminución de las poblaciones locales, por lo que los especialistas encargados de realizar los muestreos deberán causar el menor impacto en los hábitats y evitar la recolecta excesiva de especímenes (Coppolino, 2010). ...
El Phylum Mollusca representa el segundo
grupo animal más diverso en cuanto al
número de especies descritas, superado sólo
por Arthropoda. La riqueza estimada del filo
supera las 100 000 especies y se estima que
pudieran existir entre 11 000 a 40 000 especies
de moluscos aún no descritas para la ciencia
(Lydeard et al., 2004). Los gastrópodos
constituyen la clase más diversa dentro de
los moluscos con aproximadamente 150 000
especies y se calcula entre 30 000 y más de 35
000 la riqueza global de especies de hábitos
terrestres (Aktipis et al., 2008).
A pesar del origen relativamente reciente del
archipiélago cubano, la fauna de moluscos
de Cuba es una de más diversas del mundo
con más de 3 000 especies, entre terrestres
y marinas (Espinosa y Ortea, 2009). Dentro
de la malacofauna terrestre cubana se ha inventariado
aproximadamente 1392 especies
(Anexo 11.1), de las cuales 911 son pulmonados
estilomatóforos, 476 prosobranquios
y 5 pulmonados sistelomatóforos (Espinosa
y Ortea, 2009; Maceira et al., 2013; Vázquez
y Sánchez, 2014; Tabla 11.1). El alto grado
de endemismo a nivel especifico (96 %), así
como la diversidad de formas y colores en
las especies que lo conforman, distinguen a
este grupo entre los invertebrados terrestres
cubanos (Fig. 11.1).
En cuanto a la riqueza de especies de moluscos
dulceacuícolas presentes en Cuba, los
estimados son controversiales. Pointier et al.
(2005) reconocieron 42 especies (9 bivalvos
y 33 gastrópodos), mientras que Espinosa
(2013) declaró 54 especies (46 gastrópodos y
8 bivalvos). Según Espinosa y Ortea (2009) la
diferencia en los criterios se debe a que varias
especies, por su gran tolerancia fisiológica,
aparecen frecuentemente entre las fronteras
de los ambientes de agua dulce, terrestres y
marinos, por lo que es posible la ocurrencia
de omisiones o sobrestimaciones en las listas
realizadas. El número total de especies de
moluscos terrestres y dulceacuícolas conocidas
para Cuba no es definitivo, y puede variar
en dependencia de futuras revisiones taxonómicas
que se realicen a nivel de especie,
género o familia.
Aunque existe una vasta bibliografía relacionada
con los moluscos terrestres cubanos,
el nivel de conocimiento es aún insuficiente
(Espinosa y Ortea, 1999). Los estudios ecológicos
antes de la década de 1980, consistían
fundamentalmente en la descripción del
hábitat y la distribución geográfica (Henderson,
1916; Pérez, 1942; Herrera, 1945; Jaume,
1945; Jaume, 1972). En años recientes investigadores
de diferentes instituciones han realizado
algunos estudios ecológicos y actualizado
las listas de especies de moluscos en áreas
protegidas de la isla (e. g. Oliva, 2004; Maceira,
2005; Maceira et al., 2010; Hernández
y Reyes-Tur, 2013; Hernández et al., 2014).
En relación con los moluscos dulceacuícolas
la mayoría de los estudios se han enfocado
en especies de importancia médica (Perera
et al., 1995; Gutiérrez et al., 2003; Pointier et
al., 2005; Vázquez y Sánchez, 2010; Vázquez
y Sánchez, 2015).
... There is a lack of consensus among malacologists on the use of empty shells in field studies (see also Coppolino, 2010). Some researchers have treated empty shells in the same way as live specimens regardless of their condition (e.g. ...
Empty mollusc shells provide evidence of the species' presence over various temporal and spatial scales. However, the persistence of the shell can differ depending on the levels of soil pH and soil humidity. Although this is generally known, there are virtually no experimental data on shell decomposition rate and its relation to shell size and site conditions. Here we study disappearance and degradation rates of shells of nine common species covering the variation in shell size and ecological requirements of temperate European land snails. These shells were exposed to decomposition during a 3-year field experiment in six forest types, representing a gradient of soil pH and humidity. Rates of disappearance and (in larger species) of degradation were estimated by removing the exposed shells and measuring their condition after 6, 12, 24 and 36 months. The disappearance rate was modelled by generalized linear models in relation to species and forest type. The data showed an increase in shell disappearance rate from dry alkaline through to wet acidic forests, but the effect of species size outweighed that of habitat. While shells of large species only started to disappear after 3 years in wet acidic sites, most shells of small species had already disappeared by that time. In contrast, in dry habitats the loss of small shells only started after 3 years. The results clearly support the benefits of using empty shells in mollusc research, especially less damaged shells, which represent the individuals that were alive less than 2 years ago, regardless of shell size and habitat type. However, the marked differences in decomposition rate related to shell size and habitat also highlight the need to take these into account if a studied parameter is confounded with variation in shell size and/or site alkalinity or humidity.
... Some researches recommend the cardboard sheets for collecting snails (Boag, 1982;Hawkins et al., 1998). This method however, is technically unwieldy, gives questionable results (e.g. the sheet can be moved by a wind) and it is recommended rather for qualitative research of slugs (Coppolino, 2010). ...
Using non-lethal methods is especially important for the monitoring and conservation planning of endangered species and their habitats. The goal of this study is to check whether the current method of monitoring endangered micro-snail populations by soil sampling, which involves killing the snails and altering their microhabitat, could be replaced by a non-lethal method. The invasive and time-consuming soil sampling and analyzing is compared with searching the individuals by eye. Research was conducted in moist sedges meadows and seasonally inundated wetlands in western Poland and focused on two species of micro-snails differing in biology, i.e. Vertigo moulinsiana (a climbing species) and Vertigo angustior (a litter-dwelling species). Both vertiginid species are listed in the Annex II of the EU Habitat Directive and included in the IUCN Red List of Threatened Species. The results showed a significant correlation between the total number of individuals searched by eye and collected from soil samples of V. angustior and V. moulinsiana. Results of this study indicate that monitoring micro-snails by searching individuals by eye is feasible and may reduce further pressure of killing individuals of endangered species. Limitations of this method should however be taken into account – especially its inaccuracy in estimating the absolute abundance of the studied species.
... However, because of their larger size, slugs were frequently found when the cardboard pieces were collected. Species assemblages recorded with this method do not represent complete forest gastropod assemblages (Coppolino, 2010), but represent gastropod assemblages living on the surface of the forest floor (Hawkins et al., 1998). ...
... Specimens used in this study were collected in Puno, Cusco, and Huancavelica in 2010, respectively. The collecting method was qualitative visual searching (Coppolino 2010). The collected material was deposited in the malacological collection of the Museo de Historia Natural (MUSM) of Universidad Nacional Mayor de San Marcos (UNMSM) in Peru, Museu de Zoología da Universidade de São Paulo (MZUSP) in Brazil and Senckenberg Naturmuseum Frankfurt (SMF) in Germany. ...
A major taxonomic problem around the genus Megalobulimus Miller,1878, the largest land snails in the Neotropics, is plasticity of conchological characters. Here we re-describe Megalobulimus leucostoma (Sowerby, 1835) and describe two new species of Megalobulimus from Southern Peru, Megalobulimus tayacajus sp.nov. and Megalobulimus inambarisense sp.nov. These descriptions are based on both conchological and soft anatomical characters. Megalobulimus leucostoma is characterized by the presence of a retractor muscle with two insertions to the buccal mass, two small bulges on pre-rectal valve, and a geographical distribution appears limited to Cusco. Megalobulimus tayacajus sp.nov. is characterized by the presence of a retractor muscle that divides near the buccal mass, two lobed bulges on pre-rectal valve, and to date, has been found only in Huancavelica. Megalobulimus inambarisense sp.nov. is characterized by the presence of a retractor muscle with one insertion to the buccal mass, two big bulges on pre-rectal valve, and a distribution appears limited to Puno. The digestive system appears to serve as useful characters to discriminate these species and, when combined with shell and reproductive characters, may help to understand better the evolution and ecology of these snails.
... We fieldidentified and released readily identifiable live snails and took less easily identified live snails and all shells to the laboratory for identification. We did not analyze snail count data because snail activity (and hence finding live snails) is strongly affected by immediate weather conditions and empty shells, while useful for species inventories, may not reflect actual abundance (Coppolino 2010). ...
Residential yards comprise the majority of green space in urban landscapes, yet are an understudied system because of access issues and because yards may be considered biologically depauperate. Yards are purposely created and managed and, hence, qualify as designer ecosystems, a term borrowed from restoration ecology. We investigated whether yard management (watering regime, mulching, and chemical use) or dog presence affected land snail assemblage composition and described the pattern of native vs. nonnative species among yards. Land snails form an appropriate model system for yard-scale studies because snails are speciose, common, and have limited mobility. We found 32 land snail species in our survey of 61 yards in Norman, Oklahoma, USA (population size of 118,000). Snail richness in individual yards averaged nine species, with a range of three to 14 species. Native snails were found in all yards and nonnative snails were found in all but one yard. Although some of the nine nonnative species were rare, the most frequently encountered species was the nonnative Triodopsis hopetonensis. All encountered nonnative species also occur in Oklahoma plant nurseries, indicating possible introduction through the plant trade. Yard-scale watering regime and the presence of dogs were associated with differences in snail species composition but not species richness. Pesticide use and mulch type had little, if any, association with snail composition. Effects may have been diluted by treating yards as units, whereas snails were concentrated in specific microhabitats, such as under shrubs. Soil type also influenced snail assemblages and acted at a scale larger than individual yards. Considering yards as designer ecosystems facilitates investigation of how local variation in management affects biota within yards and across the residential landscape, and highlights the importance of variation among residential yards in understanding patterns of urban biodiversity.
... Animals, such as terrestrial molluscs, can play an intricate role within the alvar ecosystem. (Bishop 1977;Coppolino 2010). ...
Alvar ecosystems stand in a unique category as being under-researched, yet holding a great biodiversity within its communities. Though there may not be exhaustive research on the ecology of alvars and their constituents, this study sought to open new avenues on the alvars of Pelee Island, Ontario, Canada to compare two management strategies determined to eliminate invasive species. In 2010, thirty circular quadrats were selected to be treated with either scraping or spraying of glyphosate in order to eliminate invasive species, namely grasses. The next four years would allow researchers to examine the change in native plant communities, evaluate the efficacy of the management strategy, and survey terrestrial mollusc communities in the final year. Although the study did not find evidence to support the hypothesis that either management strategy was more efficient in the long term, scraping treatments greatly reduced the abundance of invasive species, while also depreciating terrestrial snail communities. Due to the little research performed in these localities, the current project acted as a basis for more studies to explore additional management strategies.
... However, the sampling approaches employed may limit the questions that can be addressed regarding the factors that influence small-scale distribution and abundance. A variety of collection methods have been shown to be effective for land snails (Coppolino 2010), but the challenge that remains is to now look at how sampling effort can be standardised and coupled with the collection of ecological data. Such an approach would allow a more rigorous analysis and ultimately provide a greater level of understanding of the factors influencing snail distribution and abundance. ...
Land snails are an important yet often neglected component of Australia's biological diversity. Despite high levels of diversity within this group and the identification of many narrow range endemic species as being of conservation concern, there have been few detailed studies that document the ecology and conservation requirements of the group. A range of threats has been suggested, yet relatively few have been rigorously assessed. Whilst factors such as land clearing are readily apparent and have resulted in extinctions, other threats such as climate change are not well understood. This paper reviews studies conducted on terrestrial molluscs in Australia and highlights the need for further targeted ecological research, given the likely level of on-going threats. We urge researchers to apply rigorous approaches to data collection that will enable a deeper understanding of the factors governing distribution and abundance. Approaches used in other areas of conservation biology offer considerable scope for application to land snails and for the development of appropriate conservation strategies
... However, the sampling approaches employed may limit the questions that can be addressed regarding the factors that influence small-scale distribution and abundance. A variety of collection methods have been shown to be effective for land snails (Coppolino 2010), but the challenge that remains is to now look at how sampling effort can be standardised and coupled with the collection of ecological data. Such an approach would allow a more rigorous analysis and ultimately provide a greater level of understanding of the factors influencing snail distribution and abundance. ...
Land snails are an important yet often neglected component of Australia's biological diversity. Despite high levels of diversity within this group and the identification of many narrow range endemic species as being of conservation concern, there have been few detailed studies that document the ecology and conservation requirements of the group. A range of threats has been suggested, yet relatively few have been rigorously assessed. Whilst factors such as land clearing are readily apparent and have resulted in extinctions, other threats such as climate change are not well understood. This paper reviews studies conducted on terrestrial molluscs in Australia and highlights the need for further targeted ecological research, given the likely level of on-going threats. We urge researchers to apply rigorous approaches to data collection that will enable a deeper understanding of the factors governing distribution and abundance. Approaches used in other areas of conservation biology offer considerable scope for application to land snails and for the development of appropriate conservation strategies.
... 2B–C) were collected by picking up shells directly by hand in randomly placed ,10 m 2 quadrats for 2–3 hours; quadrats at the same locality were placed ,50 m apart. Living specimens were collected from the ground, rocks, bushes, and trees, and by flipping over rocks and leaves, as well as among leaf litter (e.g., Coppolino, 2010); all living specimens found in the ,10 m 2 quadrat were considered. Dead shells were merely found entirely exposed on the soil surface and all dead shell remains (complete and broken) were collected in each quadrat. ...
Variations in the taxonomic composition of ancient land snail assemblages can potentially reflect changes in past ecosystems. The use of fossil associations as a paleoenvironmental-paleoecological proxy assumes that the original biological signature is retained, but postmortem processes can distort it. In this study, the fidelity of land snail assemblages was tested by comparing taphonomic and ecological variables recorded by live and dead, middle Holocene and Upper Pleistocene land snail shelly assemblages from San Salvador Island (Bahamas). Shells of living organisms were practically unaltered whereas dead and fossil shells were primarily affected by fragmentation, ornament loss, color loss, and carbonate coating. Tapho-nomic features fluctuated across space and time likely due to variable environmental conditions and/or time of exposure prior to shell burial. Live assemblages showed good taxonomic agreement with dead assemblages, although the later exhibited a higher number of taxa and individuals than the former. Assemblages that were moderately (dead and Holocene) and strongly (Pleistocene) taphonomically altered did not differ in species abundances, suggesting that the original biological signal was preserved. In contrast, unaltered (live and some dead) assemblages differed taxonomi-cally from moderately and strongly damaged assemblages, likely as a consequence of different scales of time-averaging rather than variable shell-specific destruction rates. Taxonomic richness and simple dominance of time-averaged land snail assemblages were similar at various interglacial time periods (,125 ka, ,5–6 ka, and today). Such apparently equivalent snail richness may suggest that the climatic-environmental and/or ecological conditions at those times were comparable to the present. INTRODUCTION
... Specimens were collected in 2008Specimens were collected in , 2009Specimens were collected in , and 2012 from different localities in the San Martín, Huánuco and Cusco regions. The collecting method was qualitative visual searching (COPPOLINO 2010) in forests and backyards. We also used shells of M. capillaceus, M. separabilis, and M. musculus from the malacological collection of the Museo de Historia Natural of Universidad Nacional Mayor de San Marcos, Lima (UNMSM). ...
Megalobulimus K. Miller, 1878 is a genus of land snails that includes the largest living snails in the Neotropics. The main goal of this paper was to review all species of Megalobulimus that have a red lip, and which are distributed in Peru. We carried out a detailed description of their shells and soft parts, and conducted a multivariate analysis on their shells and geographic distribution. There are two species reported from Peru, Megalobulimus capillaceus (Pfeiffer, 1855) and Megalobulimus separabilis (Fulton, 1903). Megalobulimus capillaceus is known to occur in three regions - San Martín, Huánuco and Cusco - but the Cusco population is undoubtedly different from all remaining populations, and is recognized herein as a new species, Megalobulimus florezi sp. nov. This species has a more elongated shell, penis club-shaped, epiphallus longer, and free oviduct longer than M. capillaceus. By contrast, the male genitalia of M. separabilis is filiform and does not present an external diverticulum in the free oviduct.
... Vegetation structure has been shown to influence snail abundance and diversity (Coppolino, 2010). Thus, habitat structure of sampling sites was characterized by recording several vegetation and ground-cover variables along a longitudinal 50-m transect that crossed the 15 x 15 m squares used for snail searches. ...
Land-use change is considered the main disturbance in landscapestructure and composition, directly affecting faunal distributionand species richness worldwide. Wildfires and natural reforestation alter habitat structure in terms of vegetation cover and also in soil composition and moisture; these processes hence trigger habitat transformations that act as opposing forces at small spatial scales. We have explored the contrasting effects of wildfires and natural reforestation on two land-snail species of the genus Xerocrassa, which are endemic in the western Mediterranean. Snails were sampled in pine and Holm oak forest, stony bare slopes and burnt sites. Both species followed a similar pattern: they were present in more than 75% of the stony bare slope sites and around 50% of the burnt sites, but were almost absent in Holm oak forests. The comparison of aerial photographs from 1956 and 2003 showed that stony bare slopes were significantly larger in 1956, this indicating that the natural reforestation might close these habitats, and consequently threaten the viability of the Xerocrassa populations. Given their limited mobility, the presence of Xerocrassa at burnt sites suggests that these species live in small and cryptic populations within the forest, surviving fire and expanding their distribution due to the appearance of adequate habitats. Our study shows that natural reforestation and fire play opposing roles in conserving Xerocrassa populations. The preservation of stony bare slopes as well as other open areas is a key management guideline to maintain landscape mosaics and help future conservation of species of open habitats such as these vulnerable endemic gastropods.
Goats browsing in woodlands, whether for livestock production goals or vegetation management (e.g., targeted grazing to control invasive plants), are at risk of meningeal worm (Parelaphostrongylus tenuis) infection. Indeed, up to 25% incidence has been observed in goats employed in vegetation management. Infection, which occurs via the consumption of an infected gastropod intermediate host, is potentially deadly in goats. We experimentally tested whether co-grazing with waterfowl could reduce goats' exposure via waterfowl consumption of gastropods. Gastropods were sampled in a deciduous woodland before and after the addition of goats alone, goats and waterfowl, or a control with no animal addition. We found that goats browsing on their own increased the abundance of P. tenuis intermediate hosts; however, when goats co-grazed with waterfowl, these increases were not observed. Importantly, waterfowl did not significantly affect overall gastropod abundance, richness, or diversity. Thus, waterfowl co-grazing may effectively reduce goat contact with infectious gastropods without detrimentally affecting the gastropod community. While co-grazing goats with waterfowl may decrease their P. tenuis exposure risk, additional research is needed to confirm whether waterfowl can actually lower P. tenuis incidence.
Terrestrial malacofaunas that inhabit islands are vulnerable to human activities. Habitat destruction, introduction of exotic species, predators, etc. are distorting the composition and distribution of indigenous snail communities. Specifically, the taxonomic discordance between live and dead assemblages may be the consequence of anthropogenic disturbances rather than natural post-mortem processes. Live-dead fidelity may hence reflect the degree of human alteration in a given locality. This approach was used to study the relative abundance of live and dead land snails from pristine and urbanized localities around San Salvador Island (Bahamas). Thirteen species were encountered from 64 samples containing 5,343 specimens. Taxonomic composition was significantly different between areas of negligible anthropogenic disturbance and those impacted by humans. Although which species of land snails are endemic to San Salvador is unknown, all identified species are native to the Caribbean region and invasive species were not encountered. However, some synanthropic species, found exclusively in urban-developed areas, have not been recovered from the local fossil record, pointing to their relatively recent introduction possibly from nearby islands. Non-metric MDS, Jaccard-Chao index, and Spearman correlation analyses indicated that dead assemblages displayed a good compositional correspondence to live communities at pristine sites, whereas considerable disparity was sometimes observed at human-modified areas. Urbanized areas probably favored the proliferation of synanthropic species whereas dead assemblages may contain anthropophobic taxa that lived there prior to recent human modification. These findings are consistent with previous live-dead fidelity studies of marine molluscan and terrestrial small-mammal assemblages, and suggest that the taxonomic discordance between live and dead assemblages of land snails may be indicative of recent anthropogenic alteration.
Inventories of land molluscs based on samples are liable to biased sampling error, because species that are present may be missed. Such errors may give a false impression of the degree of difference between faunas from similar sites, and they are confounded with genuine heterogeneity, which has considerable ecological and conservation significance. The statistical properties of such errors are examined briefly in the context of sample size and the frequency distribution of species. The effectiveness of different sampling strategies is assessed, taking account of the different life cycles and behaviour of various mollusc species. Taking random quadrats alone is not an efficient method for inventory; a combination of visual search and extraction from litter and soil is required. A set of practical guidelines is given, and the importance of good inventories, especially in oligotrophic habitats, is underlined.
The patterns of terrestrial gastropod richness within two species-rich carbonate cliff habitats in eastern Wisconsin were analyzed at two differing sample scales. Up to 23 taxa were found in 1 m 2 quadrats, and 21 taxa in 0.04 m 2 quadrats. These observations are among the highest reported globally for 1 ha or smaller samples. At the 1 m 2 scale, samples collected within 5 m of bedrock outcrops had higher richness than more distant sites. At this scale, only soil pH (not Ca, Mg, N, P, K, percent organic matter, vascular plant species richness, or surface and 20 cm depth soil temperatures) was found to significantly correlate with species richness. At the 0.04 m 2 scale, the richest sites were restricted to areas within 0.5 m of cliff bases. Comparison of maximum richness levels across varying spatial scales demonstrate that up to a third of the total fauna may co-exist in <0.04 m 2 regions (alpha diversity), up to half of the fauna may coexist in <100 m 2 regions (beta diversity), while the remainder of the taxa (gamma diversity) occurs between regions separated by at least 10 km.
The aim of the study was to elucidate on the basis of physical, floristic and edaphic features of habitat, the distribution in natural montane forests of the two endemic Carpathian clausiliid species, Macrogastra tumida and Vestia turgida . Sites sampled were in the Bieszczady National Park, East Carpathians, Poland. Snails were sampled quantitatively at 11 sites located along an elevation gradient in various floristic communities. The estimated population densities varied from 0 to 49 /m2 of forest floor. In a multivariate analysis, the first four axes accounted for 82.7% of variation in recorded environmental variation. The first axis, representing habitat fertility, correlated most strongly with the density of M. tumida. Density of V. turgida showed a weaker correlation with this axis, as it was relatively less abundant in the wettest sites, which were also the most fertile. Multiple regression models were used to determine the effects of single variables: plant species number, herb cover, slope aspect and habitat humidity were the best predictors of the snails' abundance at the sites. The interactions and intercorrelations of these factors are discussed in relation to land snail abundance.
Few studies have attempted to quantify the association between land snail communities and calcium (Ca) in upper soil horizons. If soil Ca is important to land snails, then land snail communities may be sensitive to reductions in soil Ca, including those caused by atmospheric acid deposition. In this study, snail density was estimated at ten 200m2 plots in mature forest using a litter sieving technique, and species richness was determined from litter sieving and timed searches. The most abundant snail species was the small spot, Punctum minutissimum (I. Lea), representing 34% of the specimens collected. Land snail density and species richness were positively correlated with extractable Ca, water soluble Ca, and pH in the Oe soil horizon and in the horizon below. Basal area of sugar maple, Acer saccharum Marsh., was positively associated with snail density and Ca in the Oe horizon, while basal area of red maple, Acer rubrum L., was negatively associated with snail density and Ca in the Oe horizon.
Invertebrate species represent more than 99% of animal diversity; however, they receive much less publicity and attract disproportionately minor research effort relative to vertebrates. Nonmarine mollusks (i.e., terrestrial and freshwater) are one of the most diverse and imperiled groups of animals, although not many people other than a few specialists who study the group seem to be aware of their plight. Nonmarine mollusks include a number of phylogenetically disparate lineages and species-rich assemblages that represent two molluscan classes, Bivalvia (clams and mussels) and Gastropoda (snails, slugs, and limpets). In this article we provide an overview of global nonmarine molluscan biodiversity and conservation status, including several case studies documenting the diversity and global decline of nonmarine mollusks. We conclude with a discussion of the roles that mollusks and malacologists should play in conservation, including research, conservation management strategies, and education and outreach.
Snail shells persist in the environment after death, but we know little about the rate at which shells decompose. Assumptions about the rate of shell decomposition are relevant to conservation biologists who find empty shells or biologists using empty shells to make inferences about assemblages of living individuals. I put shells in 1.6 mm mesh litter bags (excluding macro-grazers) in Delaware and northern Michigan, U.S.A. and monitored shell mass annually for 7 years. Decomposition rates differed among species, but I found no difference in rates at two sites with different habitats. Surprisingly, loss of periostracum had no effect on shell decomposition rate. At the locations and habitats studied, decomposition rate of snails averaged 6.4% per year, excluding shells that broke during the experiment (shell half life = 11.5 years), or 10.2%, including shell breakage (half life = 7.5 years). Half lives would likely be shorter if macro-grazers had access to shells. These results caution us to draw conclusions carefully when including empty shells in inferences about assemblages of living individuals.
Marine bivalve biodiversity in the waters surrounding the Florida Keys, an island archi-pelago off southern Florida, including the Florida Keys National Marine Sanctuary, was studied from ten years of original collections as well as from a critical review of museum specimens and literature data. A database of more than 12,000 records representing 389 species (half of which were ranked as abundant or common) was assembled and analyzed, resulting in a 139% increase of the known bivalve fauna of this region compared to the most recent prior (1995) checklist. Of the 389 species, 42% have not been positively recorded as live-collected, and 12.5% are represented only as singletons or doubletons. Using multivariate non-metric statistics and a priori geographic groupings along the island chain (Upper, Middle, Lower Keys; Dry Tortugas) and across the island chain (Florida Bay, shallow Atlantic waters [< 35m], deeper Atlantic waters [35−300 m]), the data showed distinct differences in benthic community structure across several spatial gradients. A pronounced northeast-to-southwest gradient was found on the Florida Bay-side of the island chain, although none was evident along the oceanside in either shallow or deep depth zones. Although they shared dominant species, the shallow-water communities of bayside and oceanside differed significantly in the percentage distributions of co-occurring species. In contrast, the deeper oceanside community differed substantially from both shallow-water groups in supporting a different set of species. A comparison of the bivalve fauna of the Keys with other well-documented faunas of the western Atlantic indicated that the Florida Keys fauna groups more closely to the Gulf of Mexico and Cuba than to eastern peninsular Florida, Yucatan, or the Bahamas. The impact of the heterogeneous nature of the dataset (live-specimen, dead-shell; and original collections, museum, and literature) is discussed and compared to analyses based on live-only data: the latter resulting in less spatial resolution but the same general patterns. In a comparison of data sources (original collections, museum records, gray literature and traditional literature), original collections were least effective (51%) in capturing the total species list despite representing approximately half of the total records. Literature was most successful (90%) in capturing the list but only when gray literature was included. Rapid assessment methods contrasted against the long-term results showed effectiveness when based on a range of sample types and habitats.
A survey of the terrestrial mollusks of the Sipsey Wilderness Area, Bankhead National Forest, in northwestern Alabama was conducted from August 2003 to May 2004. A total of 15 sites were sampled across a number of different habitat and vegetation types found within the area. A total of 50 species were found, representing 14 families and 30 genera, including 58 new county and 2 new state records. This represents a significant increase in the known diversity of the area based on a preliminary survey conducted in the 1960s, which yielded only six species. The current survey highlights the need for more detailed survey work across Alabama and the southeastern United States.
AimsTo (1) describe the distribution patterns of land-snails occurring in afromontane forest habitats on Mount Kenya, in relation to elevation and aspect; (2) explore the relations between the land-snail faunas and environmental conditions within the forests.LocationMount Kenya, Kenya.Methods
Molluscs were sampled using standardized direct search and litter sieving methods in a total of sixty-four replicated plots along four elevational transects spanning an altitudinal range from 1782 to 2851 m on the east, west, south and north-northwest sides of Mount Kenya. Elevation, vegetation type, forest structure, soil calcium, soil pH, mean annual rainfall and other environmental variables were measured on each plot. Correlation and joint regression analysis, and canonical correspondence analysis (CCA) were used to relate snail diversity and abundance, and faunal composition, to site elevation and other environmental variables.ResultsSixty-eight mollusc species were recorded during the study with transect totals between thirty-four and fifty-three species. Mean number of species and mean snail abundance ranged from 6.75 to 23.0 and 19 to 348 per plot, respectively. Overall, species richness and Shannon diversity index declined with increasing elevation. Snail abundance declined with increasing altitude along three transects and was positively related to soil pH and soil calcium, but species richness was not. Several species exhibited clear altitudinal distribution patterns. Mean annual rainfall varies greatly around the mountain and tends to decrease with altitude over the elevational range studied. Soil calcium and pH were negatively related to annual rainfall. Estimated mean annual rainfall accounted for the greatest variation in the mollusc fauna around the mountain. Faunas in forests on the drier, western side of Mount Kenya contained higher numbers of species in families that are characteristic of temperate latitudes, whereas tropical families were more prevalent on the wetter, south and east sides.Main conclusionsLand-snail diversity in Mount Kenya’s forests declines with elevation and thus follows the widespread pattern shown by most groups of organism. However, faunal variation appears to be more closely related to rainfall levels, than to altitude per se or the other environmental variables examined. The effects of rainfall on snails could either be direct, or indirect via its effects on soils or vegetation, but the study suggests that direct effects are more important. Indirect effects mediated by changes in soil chemistry appear to be less important because lower altitude sites with more strongly leached and acidic soils tend to have richer and more abundant snail faunas. The reason for the association of temperate latitude mollusc families with forests on the drier, western sides of the mountain is not clear. The number of mollusc species present in Mount Kenya’s forests is broadly comparable with that reported elsewhere in East African forests. However, overall, the data from this study and elsewhere in East Africa may provide tentative evidence for a maximum level of land-snail richness at intermediate elevations of about 1000–1500 m.
The preservation of biodiversity requires high-quality data and efficient methods for prioritizing species and sites for conservation. We examined the distribution data of 121 Hungarian land snail species in a 10 × 10 km resolution grid system. The spatial consistency of the data set varied significantly among regions, so we excluded cells with <5 species. Thus we used data from 512 out of 1052 grid cells. We prioritized Hungarian land snail species based on an additive scoring index ranging from 2 to 10 in which higher scores indicate rarer species. The index included global range size, local frequency, and a correction factor because of the biased frequency estimate or special importance of some species. We analyzed the relationship between protection status and rarity scores for each species. There were 15 unprotected species of land snails out of 30 considered rare, according to the quartile definition of rarity, and 16 protected species fell out of the score range of rare species. Four of these protected species are threatened by other than their restricted ranges (e.g., habitat loss and overexploitation). We prioritized areas by simple-ranking and complementary-areas methods based on species richness (SR), sum of rarity scores (RS), 25% rarest species richness (SQ), and a multiple-criteria index (SSQ = SR ×[SQ + 1]). In the area-selection procedures the indices based on the quartile definition of rarity (SQ and SSQ) were slightly more efficient in representing species than species richness and sum of rarity scores. We also made regional comparisons, identified hotspots at the national scale, and investigated the overlap between hotspots and existing reserve areas. The distribution of species richness and rarity among the main geographical regions of Hungary revealed differences between lowland and highland areas. Most of the hotspots were located in the mountain areas and isolated hotspots were identified in lowland areas. All species of Hungarian land snails occurred within current protected areas, but selected hotspots did not overlap with current protected areas in all cases. The location of protected areas in Hungary is adequate to preserve land snails, although we recommend that unprotected hotspots be considered for protection.Resumen: La preservación de la biodiversidad requiere de datos de alta calidad y métodos eficientes para la priorización de especies y sitios para la conservación. Examinamos los datos de distribución de 121 especies de caracoles terrestres húngaros en un sistema cuadriculado de resolución de 10 × 10 km. La consistencia espacial del conjunto de datos varió significativamente entre regiones, por lo que excluimos celdas con <5 especies. Así, utilizamos datos de 512 de 1052 celdas. Priorizamos a las especies de caracoles terrestres con base en un índice aditivo entre 2 y 10 en el que valores altos indica especies más raras. El índice incluyó el rango de tamaño global, la frecuencia local y un factor de corrección debido a sesgos en la estimación de frecuencia o la importancia especial de algunas especies. Analizamos la relación entre estado de protección y valores de rareza para cada especie. Hubo 15 especies de caracoles terrestres no protegidas en las 30 consideradas raras, de acuerdo con la definición de rareza, y 16 especies protegidas quedaron fuera del valor de especies raras. Cuatro de esas especies protegidas están amenazadas por causas distintas a su distribución restringida (e.g. pérdida de hábitat y sobreexplotación). Priorizamos áreas con métodos de clasificación simple y áreas complementarias basados en la riqueza de especies (RE), suma de valores de rareza (SR) 25% de la riqueza de especies más rara (SQ) y un índice de criterio múltiple (SSQ = RE ×[SQ + 1]). En los procedimientos de selección de áreas, los índices basados en la definición de rareza (SQ y SSQ) fueron ligeramente más eficientes en la representación de especies que la riqueza de especies y la suma de valores de rareza. También hicimos comparaciones regionales e identificamos sitios de importancia a escala nacional e investigamos el traslape entre sitios de importancia y áreas de reserva existentes. La distribución de riqueza de especies y rareza en las principales regiones geográficas de Hungría reveló diferencias entre áreas bajas y elevadas. La mayoría de los sitios de importancia se localizaron en las áreas montañosas y se identificaron sitios de importancia aislados en las áreas bajas. Todas las especies de caracoles terrestres húngaros ocurrieron dentro de áreas protegidas, pero no hubo traslape entre los sitios de importancia seleccionados y áreas protegidas en todos los casos. La localización de áreas protegidas en Hungría es adecuada para proteger a los caracoles terrestres, aunque recomendamos que se considere la protección de los sitios de importancia no protegidos.
The species richness and composition of land snail assemblages in 42 floodplain forest sites along the
Danube River in Slovakia were studied to find the main ecological gradients responsible for the variation in the faunas. We found just one, but steep, ecological gradient influencing the variation of
snail species composition among different floodplain forest types, reflected in the first detrended correspondence analysis axis, which explained 29.6% of total variation. Site scores on this axis were significantly correlated with site humidity. Significant loading on the first axis was also found for flood frequency and several vegetation descriptors. Species composition mainly reflected differences between sites without floods and the others. Species richness as well as total abundances of live individuals were not significantly controlled by any explanatory variable, although some trends could be discerned. Considering vegetation classification, substantial differences were observed between wet softwood floodplain forests and the remaining types, drier softwood forests and different types of hardwood forests, which were impossible to distinguish based on land snail assemblages. The results are discussed in relation to earlier descriptive studies, and in terms of the conservation of these threatened habitats.
Conservation and management of grasslands may involve the use of prescribed fire to reinstate a historical disturbance regime recently suppressed by humans. I used traps to describe the terrestrial mollusc community in a rare wetland prairie ecosystem of western Oregon, USA over a 3-year period in an adjacent burned and unburned wetland prairie parcel beginning 1 year following an autumn prescribed fire. Species richness was lower throughout the burned area for the duration of the study period and mollusc abundance was lower in the first postburn year, but steadily increased over time, surpassing the adjacent burned area by the third postburn year. According to Multi-response Permutation Procedure, the mollusc community in the adjacent burned area differed significantly from the unburned prairie each year since the burn, suggesting that fire history may structure the wetland prairie mollusc community. Indicator species analysis identified that Deroceras reticulatum and Monadenia fidelis were indicator species for unburned wetland prairie, while Catinella rhederi and Vertigo modesta were indicator species for burned habitat at the study site. Since fire appears to decrease wetland prairie mollusc diversity and abundance, prescribed burns should be conducted in accordance with refuges, to provide a source population for colonizing molluscs and for other animals with unknown responses to fire.
Diversidad de los caracoles terrestres en una zona caliza amenazada cercana a Estambul, Turquía.¿ Las praderas calcáreas situadas al NNO de Estambul están en peligro de ser rápidamente invadidas por la ciudad en expansión. Estudios anteriores demostraron que estos hábitats albergan especies vegetales raras, incluyendo algunos endemismos turcos. Con objeto de seguir evaluando el valor conservativo de dichos hábitats, en especial en cuanto a los invertebrados, a menudo ignorados, se han estudiado los caracoles terrestres de una zona calcárea al norte del lago Küçükçekmece y alrededor de la presa Sazlidere. Nuestros descubrimientos enfatizan la necesidad de una política de protección de estos hábitats únicos. En el área estudiada se identificaron 24 especies de caracoles terrestres. De ellas, 21 son nativas de Turquía, incluyendo tres cuya localización tipo es Estambul. Además, se considera que dos especies que se hallan en o cerca de los límites de su zona de distribución representan poblaciones periféricas especialmente merecedoras de conservación. A pesar de que la zona que rodea a la presa Sazlidere está protegida, el resto de los hábitats calcáreos está muy amenazado por el creciente desarrollo.
The land snail faunas from 72 upland and lowland grassland sites from central North America were analyzed. Sixteen of these had been exposed to fire management within the last 15 years, while the remainder had not. A total of 91,074 individuals in 72 different species were observed. Richness was reduced by approximately 30% on burned sites, while abundance was reduced by 50-90%. One-way ANOVA of all sites (using management type as the independent variable), a full 2-way ANOVA (using management and grassland type) of all sites, and a 2-way ANOVA limited to 26 sites paired according to their habitat type and geographic location, demonstrated in all cases a highly significant (up to p < 0.0005) reduction in richness and abundance on fire managed sites. Contingency table analysis of individual species demonstrated that 44% experienced a significant reduction in abundance on fire-managed sites. Only six species positively responded to fire. Comparisons of fire response to the general ecological preferences of these species demonstrated that fully 72% of turf-specialists were negatively impacted by fire, while 67% of duff-specialists demonstrated no significant response. These differences were highly significant (p = 0.0006). Thus, frequent use of fire management represents a significant threat to the health and diversity of North American grassland land snail communities. Protecting this fauna will require the preservation of site organic litter layers, which will require the increase of fire return intervals to 15+ years in conjunction with use of more diversified methods to remove woody and invasive plants.
The taxonomic challenge posed by cryptic species (two or more distinct species classified as a single species) has been recognized for nearly 300 years, but the advent of relatively inexpensive and rapid DNA sequencing has given biologists a new tool for detecting and differentiating morphologically similar species. Here, we synthesize the literature on cryptic and sibling species and discuss trends in their discovery. However, a lack of systematic studies leaves many questions open, such as whether cryptic species are more common in particular habitats, latitudes or taxonomic groups. The discovery of cryptic species is likely to be non-random with regard to taxon and biome and, hence, could have profound implications for evolutionary theory, biogeography and conservation planning.
Cardboard sheets are an efficient way of collecting large numbers of terrestrial gastropods and are useful for estimating relative densities and determining species composition of snails and slugs active on the surface of the forest floor, provided sampling is conducted under optimal weather conditions. Sheets may be less reliable, however, for quantitatively assessing the subterranean component of gastropod communities. Cardboard sheets placed on the forest floor sampled approximately 1/50 the number of gastropods estimated, using soil cores, to be in the upper 10 cm of soil beneath the sheets. The numbers collected by the two methods were not correlated (p = 0.96), but cardboard sheets produced up to 30 times as many specimens per unit of sampling time. Gastropod numbers beneath cardboard sheets peaked at near-ground temperatures around 15 degrees C and were augmented by animals moving horizontally over the surface of the litter from the surrounding area and vertically from the underlying soil, particularly when conditions were wet. Although mean (+/- S.E.) gastropod densities determined using sheets allowed to weather for a year (27.3 +/- 4.1 m(-2)) and new sheets (16.2 +/- 2.6 m(-2)) were not significantly different (p = 0.09), larger samples might confirm a tendency to prefer weathered sheets. In addition, 4 of 20 species were collected in greater numbers on weathered sheets, suggesting differential use of cardboard sheets by those species.
The richness of terrestrial gastropod communities in 19 different habitat types in a 1,300 × 1,000 km region in the Great Lakes region of North America was analyzed using 349 0.01-0.1 ha samples. Sites supporting high-richness faunas (24 or more taxa) were limited in the study region to areas south of 45°N. Only weakly significant longitudinal gradients in richness were observed, while a significant latitudinal gradient was present. When only wooded carbonate outcrops were analyzed, a significant negative correlation between richness and latitude was present only between 44°N and 45°N. Highly significant differences in richness between habitats were also observed. Carbonate cliffs harbored the richest faunas, possessing a mean greater than 20. Approximately 25% of these sites contained 24 or more taxa, with a maximum richness of 34 being recorded. Algific talus slopes and lakeshore carbonate ledges were also found to commonly harbor faunas of 17 or more taxa. All of these sites are characterized by shaded, vertical exposures of carbonate bedrock. Only two of the habitats (old fields and open dunes) were found to never support a dozen or more co-occurring taxa. Based on these analyses, carbonate cliffs and related habitats in the Great Lakes region should be included among the most important habitats on a global scale for molluscan biodiversity.
A variety of environmental parameters including soil aggregate size and earthworm granules were examined in relationship to snail abundance and diversity in different aged coppice compartments in a deciduous woodland in Sussex, England. The results indicate, in general, a positive relationship between snail abundance and intermediate sized aggregates (5mm and 2.36mm) and a negative relationship with <0.6mm and 20mm. Several individual species also followed this trend. The reason for this correlation is not clear. Ordination of snails, sites, soil fractions and other environmental variables achieves a clear geographical site separation. Soil aggregate sizes are the principal components along with pH and earthworm calcitic granules. It is clear that the soil aggregate size proportions vary substantially between coppice compartments and this may be an important factor in explaining variation in snail distribution in the study area. Earthworm granules correlate strongly with certain factors such as pH and chalk, and also with certain snail species. This link is likely to be caused by similar environmental preferences such as with pH and litter depth. Earthworms may facilitate favourable conditions for certain snails by aggregate production and litter breakdown.
Land-snail species richness in tropical rainforests tends to be high but difficult to assess because of low densities and often small shell sizes. We tested three quantitative sampling methods in primary rainforests of southeastern Madagascar. Timed searching yielded seven times as many micro-snail species (species that during at least part of their life have shells < 5 mm maximum dimension) per person-hour as either litter sampling or soil-plus-litter sampling. The number of species found in 20 m × 20 m during three person-hours of searching, however, was boosted a maximum of 38% by one eight-liter sample each of litter and soil-plus-litter. Litter sampling and timed searching both yielded more than 1.5 times the proportion of live-collected species as soil-plus-litter sampling. Sampling method was unbiased toward 12 of the 20 commonest species, but three large, presumed arboreal species were favored by timed searches; two minute, presumed burrowers by soil-plus-litter sampling; and three minute, cryptically colored species by both litter and soil-plus-litter sampling. A 1.2-mm sieve caught at least 78% of the total specimens and passed adults of 7% of species, of which the smallest adult dimension was 1.0 mm. These results suggest that the best sampling strategy is timed searching for micro-snails, while incidentally collecting macro-snails and litter-plus-soil for later picking of the 5.5-1.2 mm and the 1.2-0.85 mm, dry-sieved fractions. This strategy should be transferable to other tropical-rainforest land-snail faunas.
The historical geography of Anatolia in the period sourced by the Boǧazköy texts (Middle-Late Bronze Age) has proved an on-going problem since they first became available, and nowhere was this more acutely felt than in southern and western Anatolia, generally acknowledged as the site of the Arzawa lands, also probably the Lukka lands. A major advance has been registered since the mid-1980s, with the publication and interpretation of the Hieroglyphic inscription of Tudhaliya IV from Yalburt, and the Cuneiform treaty on the Bronze Tablet of the same king. These two documents have established that the later territory of Rough Cilicia constituted the Late Bronze Age kingdom of Tarhuntassa with its western border at Perge in Pamphylia, and that the Lukka lands did indeed occupy all of (or more than) classical Lycia in the south-west. These recognitions, by establishing the geography of the south and south-west, correspondingly reduced the areas of uncertainty in the west.
In 1997 I was fortunately able to establish the reading of the Hieroglyphic inscription attached to the long-known Karabel relief, which lies inland from Izmir in a pass across the Tmolos range between Ephesos and Sardis. This can be shown to give the name of Tarkasnawa, King of Mira, and those of his father and grandfather, also kings of Mira but with names of uncertain reading. This is the same king known from his silver seal (referred to as ‘Tarkondemos' from an early and incorrect identification), and impressions of other seals of his have more recently been found at Boǧazköy. Clearly he was an important historical figure.
The influence of environmental factors on the distribution of land molluscs in woodland habitats is discussed on a basis of a field study, preference tests, and breeding experiments. Effects of the calcium content and of the pH value of the foerna upon species number and abundance are demonstrated. It is known that in the leaves of some tree species, Ca citrate and other relatively soluble Ca salts dominate, while others are rich in Ca oxalate. In the breeding experiments, Ca citrate had a considerable, and Ca oxalate a moderate positive effect upon the reproduction of Discus rotundatus (Müll.) and Cochlicopa lubrica (Müll.). /// На основе полевых исследований обсуждаются влияние внешних факторов на распределение наземных моллюсков в лесных местообитаниях, а также результаты опытов по изучению преферендума и скрещиванию. Уста-новлено влияние содержания Са и значения рН подстилки на кодичество видов и численность животных. Известно, что в листве некоторых пород деревьев преобладает цитрат Са и другие, относительно хорошо раство-римые соли Са, в то время, как в других породах доминирует оксалат Са. В опытах по скрещиванию зарегистрировано значительное положи-тельное влияине цитрата Са и менее существенное влияние оксалата Са наразмножение Discus rotundatus (Müll.) и Cochlicopa lubrica (Müll.).
Thirty-two species and subspecies of shelled land mollusks were collected. Ninety-nine per cent of the snails were associated with some form of deciduous tree, usually aspen. Food chain relationships between aspen and land snails appear likely. The amount of available calcium also is a factor noted to be related to vegetation and affecting snail distribution. Because of these relationships, it is proposed that snail distribution be reported in terms of associated vegetation rather than altitude. Snail distribution in burned areas is also discussed. Chance distribution appears unlikely to be the only method involved and small, permanent populations within conifers are suggested to occur. Vertigo gouldi arizonensis, Gastrocopta pilsbryana and Striatura meridionalis are reported as new records for the state of Colorado.
At the Winnats Pass, a limestone gorge in North Derbyshire, two large snails are of common occurrence. One species, Cepaea nemoralis, is restricted to the south-facing side where, during the day, the majority of the snails are to be found beneath grass tussocks or on the underside of limestone outcrops. Arianta arbustorum occurs on the floor of the gorge and is abundant on the north-facing slope in tall vegetation dominated by Urtica dioica and Mercurialis perennis. The diet of the two animals is consistent with their distribution. Senescent leaves of grasses form the bulk of the diet of Cepaea nemoralis and a large component of green matter derived from the leaves of Urtica dioica and Mercurialis perennis is characteristic of the faeces of Arianta arbustorum. A. arbustorum ascends to a considerable height in the vegetation and here the snails may remain emergent throughout the day, although, as in the case of Cepaea nemoralis, movement and feeding are usually nocturnal. The low frequency of epiphragm formation in Arianta arbustorum may facilitate the exploitation of tall herbs; snails tend to be rather easily dislodged by wind action once contact with the foliage is reduced to the epiphragm. It is suggested that the reluctance of A. arbustorum to secrete an epiphragm contributes to the drought sensitivity of the species and may in part explain the failure of the snail to colonize the south-facing slope.
(1) Relative densities of slugs in thirteen stands of forest trees, near Ithaca, New York, were examined by trapping slugs with metaldehyde bait. The study plots had similar climates, soil origins, topographic positions, and histories, and so tree species was the dominant variable. (2) Slug species were not limited to one or a few closely related tree species; therefore, slugs do not form specific associations with trees. (3) Although the quantity and quality of food available to slugs depended on the tree species present, Arion subfuscus was abundant in all plots. Hence, in wooded areas, its distribution is independent of food availability. A. fasciatus and Deroceras laeve were absent from stands of pine and spruce, except where deciduous ground cover was present. It was suggested that this distribution is dependent on food availability. (4) Several slug species were most abundant under trees whose mature foliage had a high calcium content. These trees included tulip poplar, black locust, and white ash.
We examine the occurrence of regionally threatened forest land snail species on twenty-five islands with natural forest in Lake Malaren, Sweden. Threatened snail species occurred on most islands with areas of about 1 ha and above, but were absent from the six islands smaller than 0.5 ha. The number of threatened species was related to the number of not threatened species on the islands, as well as to island area. However, island area did not relate to the number of threatened species when total species richness was held constant in multiple regressions. Thus, comparably species-rich islands, but not necessarily large ones, tended to have the largest number of threatened species. Threatened snails most frequently occurred in dry forest with southern deciduous trees, and mainly on islands with a high proportion of productive soils. We suggest two reasons for the patterns found, based on the formerly larger distributions and natural disturbance regimes of rich deciduous forest. Since island area was a less reliable predictor of the number of threatened species, this easily measured variable should not be used as the sole indicator of high conservation value.
While several studies deal with the subject of the impact of fire on Mediterranean fauna and subsequent patterns of recolonization, the impact of fire on land snail communities has not yet been studied. Nevertheless, living in vegetation or in litter, land snails are highly sensitive to fire and thus constitute a good model to define the effects of fire on fauna. The aims of this study were to analyse the immediate and long-term impact of fire on the land snail communities and to reveal the patterns of post-fire recolonization within these communities. A stratified sampling scheme was carried out, throughout garrigues and forests of Provence (France), according to fire age and distances from the burned/unburned boundaries and from vegetation refuges. The data collected were studied using multivariate statistical analyses (Correspondence Analysis, Canonical Correspondence Analysis and Partial Canonical Correspondence Analysis). The main results do not agree with the original working hypotheses, i.e. land snail recolonization progressing from margins of the burned areas and from vegetation areas spared by the fire. The role of burned/unburned boundaries and vegetation refuges are not significant. Moreover, although land snail communities decrease in diversity and abundance, they are resilient to fire perturbation. In fact, one year after a fire all ecological groups are represented, which suggests a certain permanence within the malacological communities. Thus, the fire mosaic and landscape heterogeneity determine numerous scattered refuges that have proved to be difficult to locate. Finally, the composition of the post-fire land snail communities depends essentially on the habitat structure and, to a lesser degree, on their floristic composition and topography.
The effect of disturbance on land snail density in a montane subtropical wet forest was evaluated during wet (March- April) and dry (June) seasons by collecting specimens from quadrats positioned along transects that bisected treefall gaps in the Luquillo Experimental Forest of Puerto Rico. Atmospheric and litter temperature, relative humidity, litter and soil moisture, slope, and substrate type also were measured in each quadrat to determine the effect of these environmental parameters on the spatial distribution of the land snails during two sampling periods in 1989. Of the 34 species of snail known from the forest, only five occurred with sufficient frequency to permit statistical analysis. The abundances of three species (Austrosolenites alticola, Megalomastoma croceum, and Subulina octana) were not significantly different in gap versus nongap areas. In contrast, Nenia tridens and Caracolus caracolla responded to patches created by treefalls. In particular, the abundance of N, tridens was significantly higher in gaps; whereas, that of C, caracolla was significantly higher in the surrounding undisturbed forest. Such differences in distribution may be attributable to factors related to diet and body water loss rates.
Euchemotrema hubrichti (Pilsbry, 1940) was initially described as Stenotrema hubrichti by Pilsbry (1940). The species was known only from shell material, and it was originally thought to be extinct. Live specimens have since been found, but the soft-part anatomy, radula and jaws of E. hubrichti have never been described. This species is of substantial conservation concern, primarily due to our lack of knowledge about the species and its highly restricted distribution. We redescribe E. hubrichti based on material freshly collected from the type locality. Euchemotrema hubrichti is found at several sites in the Larue-Pine Hills Research Natural Area in Union County, Illinois, U.S.A., and is often abundant under loose slabs on the tops of relatively dry limestone outcrops. The shell of E. hubrichti differs from those of E. fraternum (Say, 1824) by its acute keel and low number of whorls. The genitalia of E. hubrichti are similar to those of S. stenotrema (Pfeiffer, 1842), but show a diagnostic penile inflation and lumenal twisting of the free oviduct. Partial mito- chondrial cytochrome c oxidase subunit I nucleotide sequences generated from four E. hubrichti individuals are identical, and show high similarity to available stylommatophoran sequences.
Permanent plots, in the form of square masonite boards (30 × 30 cm), were placed in a variety of habitats as a means of sampling the fauna of living gastropods on a bighorn sheep range in southwestern Alberta. Fourteen species of gastropods, ranging in age from newly hatched young to overwintered adults, were found adhering to the undersides of these boards. The number of individuals found on plots was increased in some habitats by wetting them the day before inspection. In comparing this method with other sampling procedures, I concluded that the problem of differential visibility and fragility was resolved when using these boards. Furthermore, since all gastropods recorded were living individuals, there was no need to rely on the remains of dead animals (shells) as in sifted samples, with the inherent problem of deciding which shells were from animals recently dead. The use of permanent plots enables one to sample the exact location repeatedly without destroying it and thereby to compare numbers of individuals of each species in both space and time.
ON poor, acidified soils in The Netherlands, an increasing number of great tits, Parus major, and other forest passerines, produce eggs with thin and porous shells1. Here we show that the egg-shell defects, and the related high incidence of clutch desertion and empty nests, are caused by calcium deficiency, that snail shells are the main calcium source for the laying female, but that snails are scarce on poor soils. Similar laying irregularities in birds are reported from acidified regions elsewhere in Europe2–4. We provide evidence that snails declined by a decrease in soil calcium on poor soils. Acid deposition is the main cause for decreasing calcium levels in such soils5–7. To our knowledge, this is the first experimental evidence for calcium limitation in wild birds and it reveals a previously overlooked mechanism by which acidification affects higher trophic levels of the forest ecosystem.
In many areas, soil calcium is an important limiting factor for land snail distributions. Some tree species are able to extract calcium from lower soil depths, concentrate it in their leaves and deliver it to the surface upon leaf fall. Flowering dogwood (Cornus florida) is an example of a “calcium-pumping” species and has been suggested to promote land snail diversity in woodland ecosystems. In this study, leaf tissue calcium, O- and B-horizon soil calcium and land snail diversity were compared for three common understory tree species: flowering dogwood, American beech (Fagus grandifolia) and blackgum (Nyssa sylvatica). Using a litter sieving technique, land snails were sampled underneath these three focal tree species. Land snail density, species richness and diversity were estimated for a total of 19 trees. As expected, B-horizon soil calcium was similar across all tree species, while leaf tissue calcium and O-horizon soil calcium were significantly higher for flowering dogwood. Land snail density, species richness and diversity (Shannon-Wiener Index) were also significantly higher for flowering dogwood. Calcium-pumping tree species are important ecosystem components in that they increase soil fertility and promote invertebrate diversity. Land snails are an important food and calcium source for a variety of woodland species including passerine birds, woodland salamanders, cychrine beetles, and wild turkeys. Flowering dogwood is currently seriously threatened in the southeastern United States by the parasitic dogwood anthracnose fungus (Discula destructiva). In light of the findings of this study, the implications of dogwood anthracnose may reach beyond the target species and impact multiple taxa.
The cliffs of the Niagara Escarpment provide habitat for extremely diverse communities of land snails that may be at risk as a result of recreational rock climbing. We examined the effects of rock climbing on the density, richness, diversity, and community composition of snails on the Niagara Escarpment in southern Ontario, Canada. We sampled from randomly selected climbed and unclimbed sections of cliffs on the plateau ( cliff edge ), cliff face, and talus ( cliff base ). Snail density, richness, and diversity were lower along climbing routes than in unclimbed areas, and community composition differed between climbed and unclimbed samples. These results suggest that rock climbing has significant negative effects on all aspects of the snail community on cliffs; therefore, we recommend the inclusion of gastropods in conservation plans for protected areas containing cliffs.
Resumen: Las barrancas del acantilado del Niagara proveen hábitat para comunidades extremadamente diversas de caracoles terrestres que pueden estar en riesgo debido al alpinismo recreativo. Examinamos los efectos del alpinismo en la densidad, riqueza, diversidad y composición de comunidades de caracoles del acantilado del Niagara en Ontario Meridional, Canadá. Tomamos muestras de las mesetas ( bordes de acantilados ), la cara del acantilado y el talud ( base del acantilado ) de secciones de barrancas usadas y no usadas para el alpinismo y seleccionadas al azar. La densidad, la riqueza y la diversidad de caracoles fueron más bajas en las rutas escaladas que en aquellas áreas no escaladas y la composición de la comunidad difirió entre muestras escaladas y no escaladas. Estos resultados sugieren que el alpinismo tiene impactos negativos significativos en todos los aspectos de la comunidad de caracoles en acantilados; por lo tanto, recomendamos la inclusión de gasterópodos en los planes de conservación para áreas protegidas que contengan acantilados.
Previous ordination studies of land snail community composition have been limited to four or fewer habitat types from sites separated by no more than 300 km. To investigate the nature of large-scale patterns, North American land snail assemblages at 421 sites, representing 26 habitat types and covering a 1400 × 800 km area, were ordinated using global, nonmetric multi-dimensional scaling (NMDS). These data were then subjected to model-based cluster analysis and kmeans clustering to identify the main compositional groups and most important environmental covariables. Six primary compositional groups were identified. Three of these largely represent upland forest and rock outcrop sites, while the remaining largely represent either lowland forest, lowland grassland or upland grassland habitats. The geographical location and moisture level of sites also influences community composition. A strong compositional difference exists between sites having duff vs. turf soil surface layers. Only 8% of sites were improperly classified when soil surface architecture was used as the sole predictor variable. Fully 43% of taxa exhibited significant preferences towards one of these surface types, while only 15% of relatively common (10 + occurrence) taxa showed no preferences. Twelve groups of closely related taxa within the same genus had members that favoured different surface types, indicating that differential selection pressures have existed over evolutionary time scales. While turf faunas appeared unaffected by anthropogenic disturbance, duff faunas were strongly impacted, suggesting that their conservation will require protection of soil surface architecture.
Various ecological parameters, including soil pH, calcium, and habitat complexity have been suggested in the literature as having influence on land snail abundance and diversity. I compared relationships between 15 ecological parameters and snail abundance and diversity. 5,393 snails of 72 species were collected from 60 sites in 2007. Habitat observations were recorded in the field and soil core samples taken at each site and later analyzed for soil moisture, organic matter, cation exchange capacity, pH, calcium, magnesium, zinc, potassium, phosphorus, sulfur, boron, manganese, iron and copper. Statistical analyses were run using these soil factors plus a habitat complexity index (from combined values assigned to different levels of vegetation, topography and exposed rock), for a total of 15 parameters. To reduce the number of parameters and arrive at a more biologically meaningful model, Bayesian Information Criteria analysis (BIC) was run for abundance and diversity. The resulting best-fitted BIC model for abundance contained 3 parameters (pH, S, and habitat complexity) (R2 = 0.47), all of which were positively associated with abundance in a multiple regression analysis. For diversity, the best-fitted BIC model also contained 3 parameters (Ca, Fe, and habitat complexity) (R2 = 0.54). Ca and habitat complexity showed a positive association in the multiple regression analysis, but Fe was inversely associated with diversity, suggesting Fe could potentially act as an ecological limiting factor to it. These results suggest that land snail abundance and diversity are best treated separately in analyses, as they are influenced by different variables, with the exception of habitat complexity, which is suggested to have a positive association with both abundance and diversity. The regression model equations have potential value in that they can be used to predict snail abundance and diversity in areas that have not been assessed.
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Land Snail Abundance and Diversity with Associated Ecological Variables in Six Southern Illinois Counties. M.S. Dissertation, Southern Illinois University Unionoida: Freshwater mussels The Mollusks: A Guide to Their Study, Collection, and Preservation
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