Společenstva měkkýšů podél dálnic ve vazbě na proměnné prostředí

Motorways are one of the widespread and frequently discussed landscape features, especially in Central Europe. We established three transects along the three main motorways in southeastern, southwestern, and northern directions from Prague (D1, D5, R10). These transects covered major environmental gradients of geographical position, altitude, succession, and vegetation cover. Altogether 44 land snail species (more than 26 % of the Czech Republic’s land snail fauna) were found at the 45 sites on the verges along 225 km of motorways. Surprisingly 21 % of species were such included in the Red List of the Czech Republic’s molluscs, and the endangered species Daudebardia brevipes was even present by a very abundant population. We expected the motorways to be of importance as man-made linear structure for the spreading of invasive and synathropic species, but only one such species has been found - Monacha cartusiana

Společenstva měkkýšů podél dálnic a jejich vztah k prostředí

Motorways are one of the widespread and frequently discussed landscape features, especially in Central Europe. We established three transects along the three main motorways in southeastern, southwestern, and northern directions from Prague (D1, D5, R10). These transects covered major environmental gradients of geographical position, altitude, succession, and vegetation cover. Altogether 44 land snail species (more than 26 % of the Czech Republic’s land snail fauna) were found at the 45 sites on the verges along 225 km of motorways. Surprisingly 21 % of species were such included in the Red List of the Czech Republic’s molluscs, and the endangered species Daudebardia brevipes was even present by a very abundant population. We expected the motorways to be of importance as man-made linear structure for the spreading of invasive and synathropic species, but only one such species has been found - Monacha cartusiana

Zříceniny středověkých hradů jako refugia vzácných měkkýšů v krajině

The ruins of castles have locally enriched substratum by lime, and their walls have changed into artificial screes. The ruins constitutes a very diverse habitat for rare species of snails. The castles are islands od species diversity and refuges of rare species

Land snail diversity and composition in relation to ecological variations in Central European floodplain forests and their history

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

Invasiveness Does Not Predict Impact: Response of Native Land Snail Communities to Plant Invasions in Riparian Habitats

<div><p>Studies of plant invasions rarely address impacts on molluscs. By comparing pairs of invaded and corresponding uninvaded plots in 96 sites in floodplain forests, we examined effects of four invasive alien plants (<i>Impatiens glandulifera</i>, <i>Fallopia japonica</i>, <i>F. sachalinensis</i>, and <i>F.×bohemica</i>) in the Czech Republic on communities of land snails. The richness and abundance of living land snail species were recorded separately for all species, rare species listed on the national Red List, and small species with shell size below 5 mm. The significant impacts ranged from 16–48% reduction in snail species numbers, and 29–90% reduction in abundance. Small species were especially prone to reduction in species richness by all four invasive plant taxa. Rare snails were also negatively impacted by all plant invaders, both in terms of species richness or abundance. Overall, the impacts on snails were invader-specific, differing among plant taxa. The strong effect of <i>I. glandulifera</i> could be related to the post-invasion decrease in abundance of tall nitrophilous native plant species that are a nutrient-rich food source for snails in riparian habitats. <i>Fallopia sachalinensis</i> had the strongest negative impact of the three knotweeds, which reflects differences in their canopy structure, microhabitat humidity and litter decomposition. The ranking of <i>Fallopia</i> taxa according to the strength of impacts on snail communities differs from ranking by their invasiveness, known from previous studies. This indicates that invasiveness does not simply translate to impacts of invasion and needs to be borne in mind by conservation and management authorities.</p></div

Results of t-tests for the numbers of rare snail species and individuals.

<p>Results of t-tests for the numbers of rare snail species and individuals, analyzed by generalized linear mixed models with plot invasion status (invaded/non-invaded) and invading plant species (<i>Fallopia sachalinensis</i>, <i>F. japonica</i>, <i>F.×bohemica</i> and <i>Impatiens glandulifera</i>) as fixed effects and sites with paired invaded/non-invaded plots as random intercepts. Rare species were analyzed using the function <i>glmmPQL</i> and rare individuals using <i>lmer</i> in R <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0108296#pone.0108296-R1" target="_blank">[94]</a>. Results were obtained by the function <i>summary</i> and show fixed effects based on treatment contrasts where the intercept is for the plot invasion status ‘non-invaded’ and invading plant species <i>F.×bohemica</i>. Significant invasion status×plant species interactions are in bold.</p><p>Results of t-tests for the numbers of rare snail species and individuals.</p

Results of full statistical analyses describing numbers of total, small and rare snail species and individuals between non-invaded and invaded plots.

<p>Results of full statistical analyses describing numbers of total, small and rare snail species and individuals between non-invaded plots and plots invaded by plant species <i>Fallopia sachalinensis</i>, <i>F. japonica</i>, <i>F.×bohemica</i> and <i>Impatiens glandulifera</i>. Difference is a change in counts between non-invaded and invaded plots, with negative values indicating a decrease in snail numbers on invaded sites. Values ± standard errors are on transformed scales, numbers in parentheses are original counts. Significant differences between invaded and non-invaded plots for the individual plant species are in bold.</p><p>Results of full statistical analyses describing numbers of total, small and rare snail species and individuals between non-invaded and invaded plots.</p

ANOVA tables for the numbers of total and small snail species and individuals.

<p>ANOVA tables for the numbers of total and small snail species and individuals, analyzed by linear mixed models with plot invasion status (invaded/non-invaded) and invading plant species (<i>Fallopia sachalinensis</i>, <i>F. japonica</i>, <i>F.×bohemica</i> and <i>Impatiens glandilifera</i>) as fixed effects and sites with paired invaded/non-invaded plots as random intercepts. Significant invasion status×plant species interactions are in bold. Rare species and individuals were analyzed by generalized linear models (GLMMs) for which ANOVAs are not available. Results of t-tests for the fixed effects of these GLMMs are in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0108296#pone-0108296-t003" target="_blank">Table 3</a>.</p><p>ANOVA tables for the numbers of total and small snail species and individuals.</p

Frequency distribution of the pairwise residuals between species richness of invaded and non-invaded plots across the whole dataset.

<p><b>A</b>) Frequency distribution of the pairwise residuals between species richness of invaded and non-invaded plots (richness of an invaded plot minus richness of the non-invaded plot) across the whole dataset. As the mean values of residuals in both the taxa (−6.7, and −3.1 for plants and snails, respectively) lies below zero value, and their two-sided 99% confidence intervals ([−8.5; −4.8] and [−4.9; −1.3], N = 58, df = 57) does not overlap zero, we conclude that the presence of the focal plant invaders reduce simultaneously plant and snail species richness. <b>B</b>) The lack of significant relationship (straight lines – mean trends, curved lines 95% confidence intervals) between the plant and snail species richness (in both the invaded-full lines, open symbols- and non-invaded plots-dashed lines, full symbols- as well as when using pooled data, where all the plots were analyzed together-is not shown) suggests that the reduction of plant species richness at the invaded plots is not a direct driver of the observed snail species richness reduction.</p