Wehner et al. BMC Ecol Evo (2021) 21:15 BMC Ecology and Evolution https://doi.org/10.1186/s12862-020-01741-1

RESEARCH ARTICLE Open Access Narrow environmental niches predict land‑use responses and vulnerability of land snail assemblages Katja Wehner1* , Carsten Renker2, Nadja K. Simons1, Wolfgang W. Weisser3 and Nico Blüthgen1

Abstract Background: How land use shapes biodiversity and functional trait composition of animal communities is an impor- tant question and frequently addressed. Land-use intensifcation is associated with changes in abiotic and biotic con- ditions including environmental homogenization and may act as an environmental flter to shape the composition of species communities. Here, we investigated the responses of land snail assemblages to land-use intensity and abiotic soil conditions (pH, soil moisture), and analyzed their trait composition (shell size, number of ofspring, light prefer- ence, humidity preference, inundation tolerance, and drought resistance). We characterized the species’ responses to land use to identify ‘winners’ (species that were more common on sites with high land-use intensity than expected) or ‘losers’ of land-use intensity (more common on plots with low land-use intensity) and their niche breadth. As a proxy for the environmental ‘niche breadth’ of each snail species, based on the conditions of the sites in which it occurred, we defned a 5-dimensional niche hypervolume. We then tested whether land-use responses and niches contribute to the species’ potential vulnerability suggested by the Red List status. Results: Our results confrmed that the trait composition of snail communities was signifcantly altered by land-use intensity and abiotic conditions in both forests and grasslands. While only 4% of the species that occurred in forests were signifcant losers of intensive forest management, the proportion of losers in grasslands was much higher (21%). However, the species’ response to land-use intensity and soil conditions was largely independent of specifc traits and the species’ Red List status (vulnerability). Instead, vulnerability was only mirrored in the species’ rarity and its niche hypervolume: threatened species were characterized by low occurrence in forests and low occurrence and abun- dance in grasslands and by a narrow niche quantifed by land-use components and abiotic factors. Conclusion: Land use and environmental responses of land snails were poorly predicted by specifc traits or the spe- cies’ vulnerability, suggesting that it is important to consider complementary risks and multiple niche dimensions. Keywords: Gastropoda, Land snails, Land-use intensity, Biodiversity Exploratories, Forests, Grasslands

Background Reduction of habitat and microhabitat heterogeneity Land use disturbs natural environments, changes may lead to a homogenization of plant and animal com- local geographical landscape structure and alters local munities, trigger a reduction in functional diversity and biotic and abiotic conditions, e.g. microclimate [1–6]. thus lower the capacity of an ecosystem to bufer distur- bances [7, 8]. Homogenization of animal communities by increasing land-use intensity has been shown for several *Correspondence: [email protected] taxa; e.g., in managed grasslands, 34% of plant- and leaf- 1 Ecological Networks, Technische Universität Darmstadt, hoppers species were signifcant losers (i.e. species that Schnittspahnstraße 3, 64287 Darmstadt, Germany Full list of author information is available at the end of the article were signifcantly less abundant under conditions of high

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(See fgure on next page.) Fig. 1 Trait distribution (a shell size, b number of ofspring, c light preference, d humidity preference, e drought resistance, f inundation tolerance) of snail communities among forest (grey) and grassland (white) habitats in the Swabian Alb, the Hainich-Dün and the Schorfheide-Chorin. Traits are given as community weighted mean (CWM). Diference among habitats per region are tested using an ANOVA (asterisks), diferences between regions are tested by a posthoc Tukey test (letters). Signifcances: ns not signifcant, *p < 0.05, **p < 0.01, ***p < 0.001

land-use intensity) of land-use intensifcation, particu- In the present study, we investigated land snail com- larly increases in mowing frequency had a negative efect munities at forest and grassland sites in diferent regions [9]. of Germany, which were characterized by diferent land- Land snails are an important macroinvertebrate group use types and intensities. We aimed to test whether the that is directly and indirectly involved in ecosystem pro- trait composition of the snail community is infuenced by cesses such as litter decomposition or nutrient cycling land-use intensity (and soil conditions). We then tested [10, 11]. Tere is a natural north–south and west–east the responses of each snail species to land-use intensity; gradient of snail species distributions and abundances ‘winners’ signifcantly increase in abundance and occur- within Europe; species richness increases from north to rence with land-use intensity, whereas ‘losers’ signif- south and to a lesser extent from west to east which is cantly decrease compared to the null model [9, 39]. We linked to regional and ecological diferences and the land- than compared these responses with the snail species’ use history [12]. Snail species also difer in their tolerance habitat association; i.e. we asked whether species that to abiotic factors (pH, soil moisture), and vary greatly in only occasionally occur in forests are more afected by life-history parameters (e.g., lifespan, development, num- forest management than species that are specialized to ber of ofspring, food requirement, shell size) and general forest habitats. On the other hand, do species that are behavior [13] which also afect their distribution. Varia- grassland specialist sufer less from grassland manage- tion in body size and diet seems to be especially impor- ment than those only occasionally occurring in grass- tant for structuring snail communities [14] as well as the lands? Finally, we compared our fndings of the land-use species-specifc tolerance to a variety of environmental efects and the ‘winner/loser’ status of a species with its factors which can result in nested communities at a spe- putative vulnerability (Red List status), to test if losers cifc site [15, 16]. of land-use intensifcations in forests and grasslands are Studies on trait composition of snail communities in those species that are classifed as vulnerable. Sweden pointed to the importance of the species’ niche- width and the importance of local environmental condi- Results tions over spatial variables [17]. While tolerance-related Response to land use traits such as humidity preference or inundation toler- Te trait composition of land snail communities dif- ance were positively associated with abiotic soil moisture, fered strongly between forests and grasslands within a large amount of variation remained unexplained [17], regions, indicated by a strong diferentiation of commu- which may be related to land use. Te impact of land nity-weighted mean trait values (CWMs). Assemblages use and its intensity on land snail communities is less of forest species consisted of larger species, consistently intensively investigated although most land snail species showed lower light and higher humidity preference, are characterized by a limited mobility and therefore are lower drought resistance and mostly lower inundation vulnerable to human introduced habitat changes [15, 18– tolerance than grassland assemblages; diferences in the 20]. Changes in abiotic factors such as soil pH, soil mois- number of ofspring were inconsistent among forest and ture, soil calcium content, leaf litter depth, soil surface grassland habitats (Fig. 1). structure or the type of vegetation have been shown to In forests, land-use intensity and abiotic conditions sig- alter snail communities [15, 21–25]. Also land-use factors nifcantly infuenced the CWMs of all traits investigated, such as the proportion of wood harvested in forests or the although often in a diferent way across regions (Table 1, amount of grazing livestock in grasslands can infuence Additional fle 1: Appendix 1; see interaction terms with snail communities directly and/or indirectly [20, 26, 27]. region). Similarly, in grasslands the trait composition of In addition, disturbances by diferent land-use types and snail communities was signifcantly infuenced by most intensities may alter the trait composition of snail com- land-use components and abiotic conditions (Table 2, munities on the regional level; i.e. the presence of conif- Additional fle 1: Appendix 1). erous timber may favor snail communities with difering In forest habitats, some 4% of all species were ‘losers’ traits than communities in natural deciduous stands. of the combined forest management index (i.e. they were signifcantly less common in intensively used forests), Wehner et al. BMC Ecol Evo (2021) 21:15 Page 3 of 23

a Shell size (CWM) [mm] b Number of offspring (CWM) [per clutch] a b a a b c *** *** *** *** *** ***

c Light preference(CWM) d Humiditypreference(CWM)

a b c a b c *** *** *** *** *** *** High High

Moderate Moderate

Low Low

e Droughtresistance(CWM) f Inundation tolerance(CWM) a b c a b c *** *** *** *** ns *** High High

Moderate Moderate

Low Low Wehner et al. BMC Ecol Evo (2021) 21:15 Page 4 of 23 0.220 0.130 0.580 0.141 0.006 0.002 0.004 0.001 0.009 0.005 0.028 0.018 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 p p 9.763 1.506 4.818 2.048 0.026 5.600 1.964 6.670 5.143 7.151 5.603 9.923 18.055 6.785 6.904 5.257 30.382 94.739 19.836 92.792 32.624 15.098 107.554 F F 25.064 17.021 13.687 16.725 121.683 20.883 26.525 11.325 20.535 102.981 102.744 9.859 0.447 1.655 0.067 2.687 9.807 0.229 0.195 9.056 0.948 0.052 8.665 1.523 1.410 9.865 0.269 0.189 1.250 Sum Sq Sum Sq 0.969 1.340 2.348 1.047 1.870 1.603 1.246 2.558 1.563 10.763 3.874 4.873 0.634 0.975 1.051 1.966 2 2 1 df df 2 2 2 1 2 2 1 2 2 1 1 2 2 2 1 2 2 1 1 2 1 2 2 1 2 2 1 2 2 1 2 Region Region FORMI Light preference (CWM) preference Light (CWM) tolerance Inundation Region FORMI:Region FORMI:Region FORMI Region Inonat:Region Inonat Region Idwcut:Region Idwcut Inonat Region Region Iharv:Region Iharv Inonat:Region pH:Region pH Soil moisture Region Idwcut Idwcut:Region Region Iharv Iharv:Region Region pH pH:Region Region Soil moisture Soil mositure:Region 0.172 0.429 0.099 0.003 0.002 0.021 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 p p 8.142 5.714 8.293 9.739 5.345 1.766 0.846 2.713 6.811 16.574 73.221 28.963 33.232 17.868 72.625 66.118 22.890 43.046 66.613 37.711 23.379 23.797 146.369 504.612 101.500 F F 171.359 156.584 167.238 581.538 180.564 512.182 526.638 583.257 541.944 1.589 3.511 2.709 1.554 1.686 3.426 0.560 1.122 0.801 0.470 0.260 753 14.036 46,655 4692 Sum Sq Sum Sq 16.025 14.773 2805 16.400 3652 49,336 17.439 3128 166 48,101 1772 49,503 80 121 52,165 2091 1112 637 50,664 2 2 2 2 1 1 df df 2 2 1 2 2 1 1 2 2 1 2 2 2 2 1 1 1 2 2 1 2 2 1 2 2 1 2 2 FORMI:Region FORMI:Region Region Region FORMI FORMI Number of ofspring (CWM) Number of ofspring (CWM) resistance Drought Inonat:Region Region Inonat Idwcut:Region Region Idwcut Inonat Iharv:Region Region Iharv Inonat:Region Region pH:Region Region pH Soil moisture Idwcut Idwcut:Region Region Iharv Region Iharv:Region pH Region pH:Region Soil moisture Soil mositure:Region Region 0.220 0.010 0.002 0.005 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 p p 6.626 6.492 1.509 5.261 34.106 23.619 75.683 37.837 47.672 21.527 46.127 54.282 24.602 21.051 26.884 75.899 79.396 55.324 19.495 13.347 14.358 24.994 28.714 177.015 433.889 F F 208.013 168.776 170.392 451.940 155.513 438.393 453.818 489.548 442.215 2.780 1.345 3.280 0.228 1.578 1.690 0.493 0.934 1.948 2.750 2.921 285.4 457.3 12.584 5243.8 Sum Sq Sum Sq 14.311 326.4 12.371 253.2 12.937 5435.5 11.270 337.7 238 5351.8 82.4 177.2 5601.9 9 298.8 5852.2 181.3 55.4 5584.7 2 2 1 1 2 1 2 2 df df 2 1 2 1 2 1 2 2 2 1 2 2 1 2 1 2 2 1 2 2 1 2 2 1 2 2 Infuence of land-use parameter and abiotic factors on the trait composition of snail communities in forest habitats in forest of snail communities composition and abiotic factors on the trait of land-use parameter Infuence FORMI:Region FORMI:Region FORMI FORMI Inonat:Region Inonat Region Region 1 Table (CWM) size Shell (CWM) Humidity preference Idwcut:Region Idwcut Region Inonat Iharv:Region Iharv Region Inonat:Region pH:Region pH Region Region Soil moisture Region Idwcut Idwcut:Region Region Iharv Iharv:Region Region pH pH:Region Region Soil moisture Soil mositure:Region Region Wehner et al. BMC Ecol Evo (2021) 21:15 Page 5 of 23 0.520 0.008 p 0.654 4.881 F 0.125 Sum Sq 0.935 2 df 2 Region Inundation tolerance (CWM) tolerance Inundation Soil mositure:Region 0.004 < 0.001 p 5.441 180.452 F 0.529 17.561 Sum Sq 2 2 df Region Soil mositure:Region Drought resistance (CWM) resistance Drought < 0.001 < 0.001 p 13.867 156.227 F 1.020 11.494 Sum Sq 2 2 df (continued) Soil mositure:Region Region 1 Table in bold given are values Signifcant Iharv cuts, proportion with saw proportion Idwcut harvested of dead wood of wood trees, Inonat proportion index, management of non-native forest FORMI Humidity preference (CWM) Humidity preference Wehner et al. BMC Ecol Evo (2021) 21:15 Page 6 of 23 0.004 0.019 0.015 0.016 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 p p < 0.001 0.024 0.527 < 0.001 0.314 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 0..502 0.088 < 0.001 < 0.001 0.035 0.234 5.392 5.486 5.119 5.960 0.640 4.152 1.014 0.690 6.939 4.478 1.453 26.071 25.385 28.818 59.483 74.999 20.306 10.158 22.760 18.770 99.785 15.814 10.771 310.828 F F 304.664 107.017 349.538 283.187 369.382 109.120 287.467 113.050 105.097 104.523 3.626 1.765 0.789 0.401 0.412 3.843 0.397 0.103 0.604 4.327 9.133 1.236 0.080 1.605 1.719 2.836 1.278 0.172 0.549 1.704 0.360 0.235 43.230 Sum Sq Sum Sq 44.594 17.237 46.61 41.199 44.982 17.245 19.377 17.080 16.131 16.624 16.903 2 2 1 df df 2 2 1 2 1 2 2 1 2 2 2 1 2 2 1 2 1 1 2 2 1 2 2 1 2 2 1 2 2 1 2 LUI:Region Region LUI Light preference (CWM) preference Light (CWM) tolerance Inundation Mowing:Region Region Mowing Region LUI Grazing:Region Region Grazing LUI:Region Fertilization:Region Region Fertilization pH:Region Region pH Region Mowing Soil moisture Mowing:Region Region Grazing Grazing:Region Region Fertilization Fertilization:Region Region pH pH:Region Region Soil moisture Soil mositure:Region 0.774 0.055 0.185 0.368 0.097 0.675 0.001 0.001 0.018 0.018 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 p p 0.175 8.252 4.042 9.192 0.082 6.403 3.703 10.237 7.799 29.160 1.690 0.810 2.337 5.575 30.582 16.489 33.505 55.976 32.983 73.056 F F 73.285 233.853 71.585 32.926 72.506 68.779 227.152 25.671 268.169 207.321 287.605 140.899 174.950 216.410 0.358 2.844 0.002 767 Sum Sq Sum Sq 0.250 2.858 4368 0.072 35,030 0.295 2.719 0.623 0.067 2.870 0.016 14 0.093 2.726 0.111 1301 35,805 0.496 2185 2356 38,316 2672 33,070 645 6862 35,255 8636 4604 24,423 15,105 2 2 1 1 df df 2 2 2 1 2 2 2 1 2 2 1 1 2 2 1 2 2 1 1 2 2 1 2 2 2 2 1 2 2 1 LUI:Region Region LUI LUI Number of ofspring (CWM) Number of ofspring (CWM) resistance Drought Mowing:Region Region LUI:Region Mowing Region Grazing:Region Region Grazing Fertilization:Region Region Fertilization Mowing pH:Region Region pH Mowing:Region Region Soil moisture Grazing Grazing:Region Region Fertilization Region Fertilization:Region pH:Region Region pH Soil mositure:Region Region Soil moisture 0.215 0.193 0.306 0.172 0.377 0.533 0.251 0.261 0.197 0.540 0.039 0.011 0.008 0.036 0.044 0.009 0.012 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 p p 1.542 1.050 4.496 1.866 4.872 27.882 4.283 14.988 1.647 16.989 0.781 56.964 31.830 3.350 0.389 3.146 6.763 1.385 1.348 1.664 5.791 0.488 348.964 F F 333.045 71.659 349.785 327.885 430.070 72.796 258.049 71.464 70.534 85.099 95.150 9.841 5.600 2.651 0.582 0.198 4.300 1.652 0.343 1.825 3.182 1.020 4.880 8.740 0.510 8.230 8.840 3.620 3.430 2.120 0.490 17.468 43.980 11.580 123.421 Sum Sq Sum Sq 125.799 187.310 128.553 122.809 131.880 189.840 187.060 189.430 216.910 190.300 2 1 1 2 1 2 2 df df 2 1 2 2 2 1 2 1 2 1 2 2 1 2 2 1 2 2 1 2 2 2 1 2 2 1 2 Infuence of land-use parameter and abiotic factors on the trait composition of snail communities in grassland habitats in grassland of snail communities composition and abiotic factors on the trait of land-use parameter Infuence LUI:Region LUI LUI Mowing:Region Mowing LUI:Region Region 2 Table (CWM) size Shell (CWM) Humidity preference Grazing:Region Grazing Region Region Fertilization:Region Fertilization Region Mowing pH:Region pH Region Mowing:Region Soil moisture Region Region Grazing Grazing:Region Region Fertilization Fertilization:Region Region pH:Region pH Region Soil mositure:Region Soil moisture Region Wehner et al. BMC Ecol Evo (2021) 21:15 Page 7 of 23 0.877 < 0.001 p 0.131 229.127 F 0.018 30.888 Sum Sq 2 2 df Soil mositure:Region Region Inundation tolerance (CWM) tolerance Inundation < 0.001 < 0.001 p 8.055 64.560 F 0.312 2.497 Sum Sq 2 2 df Soil mositure:Region Region Drought resistance (CWM) resistance Drought 0.001 < 0.001 p 8.640 275.743 F 2.945 93.991 Sum Sq 2 2 df (continued) land-use intensity Soil mositure:Region Region 2 Table in bold given are values Signifcant LUI Humidity preference (CWM) Humidity preference Wehner et al. BMC Ecol Evo (2021) 21:15 Page 8 of 23

whereas 12% were ‘winners’ and thus increased with for- Habitat association est management intensity (Table 3). Te proportions of Snail species difered in their habitat association and their non-native trees (4% losers vs. 8% winners) and the pro- distribution among regions (Fig. 2). However, efects of portion of dead wood with saw cuts (6% losers vs. 8% land-use management components and abiotic factors in winners) revealed a similar pattern, but for the propor- forests were independent of the species’ habitat associa- tion of wood harvested the percentage of losers (12%) tion, i.e. species that occurred in forests at low frequen- exceeded that of winners (8%). cies (e.g., 25% of the individuals in Cochlicopa lubrica; In grasslands, many species were predominantly found Fig. 2) were equally afected by land-use intensifca- at low land-use intensities (LUI); 21% of all species were tion as species that are exclusively found in forests (e.g., signifcant losers and only Monacha cartusiana prof- Cepaea hortensis) ­(F1,49 = 0.14, p = 0.71, Fig. 2, Additional ited from high LUI (Table 4). However, single land-use fle 14: Appendix 14). In contrast, grassland species that components in grasslands had only weak efects. Graz- predominately prefer grassland habitats were less toler- ing intensity positively afected Cecilioides acicula and ant to fertilization than species that also occur in forests Cepaea hortensis, but showed no negative impact. Simi- ­(F1,50 = 5.84, p = 0.019, Fig. 3a, Additional fle 15: Appen- larly, mowing (2% losers and 2% winners) and fertiliza- dix 15). Furthermore, grassland “specialists” were sig- tion (4% losers and 4% winners) had a very little impact nifcantly associated with higher pH values (F­ 1,49 = 9.21, compared to the combined LUI. p = 0.004, Fig. 3b). However, in both forests and grasslands, species’ land- use responses (i.e. their ‘winner/loser’ status) were inde- Species’ vulnerability pendent of their traits; i.e. losers in forests or grasslands Across forests and grasslands, 75% of the 61 snail spe- were neither characterized by a smaller or larger shell cies found are currently not threatened or endangered size nor by lower or higher numbers of ofspring nor by according to their Red List status (Tables 3, 4). Neverthe- lower or higher light preference etc. (Additional fles 2– less, Nesovitrea petronella, Candidula unifasciata and 15: Appendix 2–15). Granaria frumentum are regarded as ‘endangered’ while Vallonia enniensis is ‘highly endangered’ and V. angustior is listed on the FFH directive. Response to abiotic factors Tere was no statistical support that a negative Although niches of common land snail species for soil pH response to land-use intensity of a certain species and soil moisture were generally broad, some diferentia- (“loser”) is associated with a high vulnerability of the tion was found in the communities of both habitats. In species, neither in forests nor in grasslands (Table 5). A forests, Aegopinella pura, the genus Carychium, Coch- better predictor for the species’ vulnerability in forests licopa lubrica, Ena montana and Vitrea contracta were was a relatively low number of sites in which the species signifcantly associated with higher pH values (Table 3) occurred, and in grasslands both a low occurrence and and Cepaea hortensis, Euconulus fulvus, Nesovitrea ham- a low total abundance corresponded to a higher vulner- monis, Vallonia pulchella and Vitrinobrachium breve ability (Table 5). Furthermore, the 5-dimensional niche were found at sites with low pH (Table 3). Furthermore, hypervolume based on the species’ tolerance to land- A. pura and Carychium tridentatum were associated with use components and abiotic conditions was signifcantly high soil moisture in forests and Ceciliodes acicula, E. ful- correlated with the species’ vulnerability, hence species vus, N. hammonis, Punctum pygmaeum, Trochulus stri- with a small niche hypervolume are more vulnerable in olatus and V. pulchella were found at low soil moisture both forests (Spearman rank test: S 20,091, p 0.0004; values (Table 3). = = Fig. 4a) and grasslands (Spearman rank test: S = 15,547, Grassland sites had a higher mean pH (6.7) as com- p 0.003, Fig. 4b). pared to forest soils, and many snail species (e.g., Can- = didula unifasciata, the genus Carychium, Granaria Discussion frumentum, Pupilla muscorum, Vertigo antivertigo) were Response to land use and abiotic factors associated with higher pH values (Table 4). Only N. ham- monis was signifcantly more common on sites with low Land snail species are slow-dispersing organisms, and pH. Soil moisture niches of grassland species were even historical infuences are of general importance for their broader than those of pH. Te genus Carychium, Tro- distribution [28]. Teir diversity and heterogeneity is chulus hispidus and Vallonia pulchella were found at modifed by predation, parasitism, competition, abiotic high moisture values, while C. unifasciata, Discus rotun- environmental gradients, natural barriers and distur- datus, Truncatellina cylindrica, V. excentrica were asso- bances [16]. While abiotic and vegetation parameters can ciated with low soil moisture (Table 4). be used to predict snail communities, disturbances by Wehner et al. BMC Ecol Evo (2021) 21:15 Page 9 of 23 Soil moisture Neutral Neutral Neutral Neutral Mid-specialist "High" Neutral Neutral "High" "Low" Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral "Low" Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral "Low" Neutral Neutral Neutral Neutral "Low" Neutral pH Neutral Neutral Neutral Neutral Mid-specialist "High" Neutral "High" "High" Neutral "Low" Neutral Neutral "High" Neutral Neutral Neutral "High" "Low" Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral "Low" Neutral Neutral Neutral Neutral Neutral Neutral Iharv Neutral Neutral Neutral Neutral Loser Neutral Neutral Neutral Neutral Loser Loser Neutral Neutral Winner Neutral Neutral Neutral Neutral Neutral Neutral Loser Winner Neutral Winner Neutral Neutral Neutral Loser Neutral Neutral Winner Neutral Neutral Neutral Idwcut Neutral Neutral Neutral Neutral Neutral Neutral Loser Winner Neutral Neutral Loser Neutral Neutral Winner Neutral Neutral Neutral Neutral Mid-specialist Neutral Loser Winner Neutral Neutral Neutral Winner Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Inonat Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Loser Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Winner Neutral Neutral Neutral Neutral Neutral Winner Neutral Neutral Neutral Loser Neutral Neutral FORMI Neutral Neutral Winner Neutral Neutral Neutral Neutral Winner Neutral Neutral Loser Neutral Neutral Winner Neutral Neutral Neutral Mid-specialist Neutral Neutral Loser Winner Neutral Neutral Neutral Neutral Neutral Winner Neutral Neutral Neutral Neutral Neutral Neutral 2 4 2 1 3 1 6 2 4 61 16 15 24 82 57 14 62 27 12 86 77 87 12 15 23 12 Total Total abundance 123 422 115 612 362 118 169 180 4 1 1 3 1 5 2 1 7 2 2 Occurrence 37 11 62 11 91 14 37 74 26 15 12 29 19 97 10 52 27 24 46 59 11 10 50 Region AHS AH AHS AH AHS AH AH AHS AHS AH H HS AHS A AH AHS AH AHS A AH H A A AH H AH AHS S H H AH AHS HS A RedList * * * * * * * * * * * * * V * * V * G * * * V * * * * 2 * * 3 * V * Red list status, occurrence and total occurrence Red list status, of snail abundance species in the Swabian the Hainich-Dün (A), Alb (H) and the Schorfheide-Chorin (S) in forest 3 Table habitats Species (O.F. Müller, 1774) Müller, aculeata (O.F. Acanthinula (Linnaeus, 1758) hispidus (Linnaeus, Trochulus Aegopinella nitens (Michaud, 1831) Aegopinella (Draparnaud, 1805) nitidula (Draparnaud, Aegopinella (Alder, 1831) (Alder, pura Aegopinella (Linnaeus, 1758) Arianta arbustorum (Linnaeus, O.F. Müller, 1774 Müller, Carychium minimum O.F. (Risso, 1826) Carychium tridentatum (Risso, (O.F. Müller, 1774) Müller, acicula (O.F. Cecilioides (O.F. Müller, 1774) Müller, hortensisCepaea (O.F. (Linnaeus, 1758) (Linnaeus, nemoralis Cepaea (Strom, 1765) Clausilia bidentata (Strom, (O.F. Müller, 1774) Müller, (O.F. lubrica Cochlicopa (Porro, 1838) (Porro, lubricella Cochlicopa (Montagu, 1803) laminata (Montagu, Cochlodina (O.F. Müller, 1774) Müller, (O.F. Discus rotundatus (Draparnaud, 1801) Ena montana (Draparnaud, Euconulus fulvus (O.F. Müller, 1774) Müller, fulvus (O.F. Euconulus (Draparnaud, 1801) strigella (Draparnaud, Euomphalia (O.F. Müller, 1774) Müller, (O.F. obvoluta Helicodonta Linnaeus, 1858 Helix pomatia Linnaeus, (Schröter, 1784) Isognomostoma isognomostomos (Schröter, a (Draparnaud, 1801) a (Draparnaud, plicatul Macrogastra (Draparnaud, 1801) (Draparnaud, ventricosa Macrogastra O.F. Müller, 1774 Müller, Monacha cartusiana O.F. O.F. Müller, 1774 Müller, O.F. Monachoides incarnatus (Strom, 1765) hammonis (Strom, Nesovitrea (L. Pfeifer, 1853) (L. Pfeifer, petronella Nesovitrea (O.F. Müller, 1774) Müller, (O.F. Oxychilus cellarius (Beck,Oxychilus 1837) draparnaudi Platyla polita (Hartmann, 1840) (Draparnaud, 1801) (Draparnaud, pygmaeum Punctum (Linnaeus, 1758) (Linnaeus, muscorum Pupilla (Draparnaud, 1801) oblonga (Draparnaud, Succinella Wehner et al. BMC Ecol Evo (2021) 21:15 Page 10 of 23 Soil moisture Neutral "Low" Neutral Neutral Neutral "Low" Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral pH Neutral Neutral Neutral Neutral Neutral "Low" Neutral Neutral Neutral "High" Neutral Neutral Neutral "Low" Neutral Iharv Neutral Neutral Neutral Neutral Loser Neutral Neutral Neutral Neutral Neutral Mid-specialist Neutral Neutral Neutral Neutral Idwcut Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Inonat Neutral Neutral Neutral Neutral Neutral Neutral Winner Neutral Neutral Neutral Neutral Neutral Neutral Neutral Winner FORMI Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Winner Neutral Neutral 1 3 1 9 3 1 2 2 12 25 25 38 89 30 27 Total Total abundance 8 1 2 7 1 3 2 1 2 2 Occurrence 16 14 40 16 11 Region AH A S AS AH AHS A HS AS AHS AH H S A AS RedList * V V * * * 3 * 3 * * G * * * (continued) 3 Table Species in bold given are values Signifcant of dead (Inonat), the percentage trees of non-native (FORMI), the percentage index management forest land-use parameters the following loser or mid-specialist to as winner, assigned land use are to Species responses harvesting of tree (Iharv) and the percentage cuts (Idwcut) with saw wood 1 = critically endangered, V = near threatened, unknown to R = very extent, G = endangered risk rare, (least concern), * = no current Red List status: respectively. species, and high-gradient low- to refer “high” and “Low” 3 = vulnerable 2 = endangered, (Draparnaud, 1801) (Draparnaud, sericeus Trochulus (C. Pfeifer, 1828) Pfeifer, striolatus (C. Trochulus (C. Pfeifer, 1828) Urticicola Pfeifer, (C. umbrosus (O.F. Müller, 1774) Müller, (O.F. costata Vallonia Sterki, 1893 excentrica Vallonia (O.F. Müller, 1774) Müller, pulchella (O.F. Vallonia Jefreys, 1830 Vertigo angustior Jefreys, (Draparnaud, 1801) (Draparnaud, Vertigo pygmaea Vertigo substriata (Jefreys, 1833) (Westerlund, 1871) contracta Vitrea (O.F. Müller, 1774) Müller, crystallinaVitrea (O.F. (Studer, 1820) diaphana (Studer, Vitrea (O.F. Müller, 1774) Müller, Vitrina pellucida (O.F. (A. Férussac, 1821) Férussac, (A. breve Vitrinobrachium (O.F. Müller, 1774) Müller, nitidus (O.F. Zonitoides Wehner et al. BMC Ecol Evo (2021) 21:15 Page 11 of 23 Mid-specialist Soil moisture Neutral Neutral Neutral Neutral Neutral Neutral Neutral "Low" "High" "High" Neutral Neutral Neutral Neutral Neutral "Low" Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral pH "High" Neutral Neutral Neutral Neutral Neutral Neutral "High" "High" "High" Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral "High" "High" Neutral Mid-specialist Neutral Neutral Neutral "Low" Neutral Neutral "High" Neutral "High" Neutral Neutral Neutral Fertilization Neutral Neutral Mid-specialist Neutral Neutral Neutral Neutral Neutral Loser Neutral Neutral Neutral Neutral Neutral Neutral Winner Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Winner Neutral Neutral Neutral Neutral Neutral Neutral Neutral Mowing Neutral Neutral Neutral Neutral Neutral Winner Neutral Neutral Neutral Neutral Neutral Loser Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Grazing Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Winner Winner Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral LUI Loser Neutral Neutral Neutral Loser Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Loser Loser Neutral Neutral Neutral Winner Neutral Loser Neutral Neutral Neutral Loser Neutral Neutral Neutral Neutral Total abundance Total 215 1 14 2 15 2 38 46 381 142 2 3 546 1 1 28 1 1 1 18 28 1 6 3 34 3 35 2 1 1 28 1087 530 165 57 Occurrence 29 1 9 2 9 1 21 9 23 30 2 3 77 1 1 12 1 1 1 2 11 1 3 3 2 3 16 1 1 1 14 70 12 13 25 Region AHS A AH AH AHS H AH AH AS AHS AH AH AHS H A AHS H S A A AH A H AH HS AH AHS A A S AHS AHS S S AHS RedList * G * * * * * 2 * * * * * * * * * * G 2 3 * * * * * * * 3 2 * V R * * Red list status, occurrence and total of snail the Hainich-Dün abundance occurrence species in the Swabian (H) and the Schorfheide-ChorinRed list status, (A), Alb (S) in grassland 4 Table habitats Species (Linnaeus, 1758) hispidus (Linnaeus, Trochulus (Draparnaud, 1801) (Draparnaud, Abida secale (Draparnaud, 1801) (Draparnaud, sericeus Trochulus (O.F. Müller, 1774) Müller, aculeata (O.F. Acanthinula Aegopinella nitens (Michaud, 1831) Aegopinella (Draparnaud, 1805) nitidula (Draparnaud, Aegopinella (Alder, 1831) (Alder, pura Aegopinella (Poiret, 1801) (Poiret, unifasciata Candidula O.F. Müller, 1774 Müller, Carychium minimum O.F. (Risso, 1826) Carychium tridentatum (Risso, (O.F. Müller, 1774) Müller, acicula (O.F. Cecilioides (O.F. Müller, 1774) Müller, hortensisCepaea (O.F. (O.F. Müller, 1774) Müller, (O.F. lubrica Cochlicopa (Montagu, 1803) laminata (Montagu, Cochlodina Waldén, Waldén, 1966 aspera Columella (O.F. Müller, 1774) Müller, (O.F. Discus rotundatus (Draparnaud, 1805) diaphana (Draparnaud, Eucobresia Euconulus fulvus (O.F. Müller, 1774) Müller, fulvus (O.F. Euconulus (Draparnaud, 1801) strigella (Draparnaud, Euomphalia (Draparnaud, 1801) frumentum (Draparnaud, Granaria (Linnaeus, 1858) itala (Linnaeus, Helicella (O.F. Müller, 1774) Müller, (O.F. obvoluta Helicodonta Linnaeus, 1858 Helix pomatia Linnaeus, (Draparnaud, 1801) (Draparnaud, ventricosa Macrogastra O.F. Müller, 1774 Müller, Monacha cartusiana O.F. O.F. Müller, 1774 Müller, O.F. Monachoides incarnatus (Strom, 1765) hammonis (Strom, Nesovitrea (Beck,Oxychilus 1837) draparnaudi Platyla polita (Hartmann, 1840) Pseudotrichia rubiginosa Pseudotrichia (Draparnaud, 1801) (Draparnaud, pygmaeum Punctum (Linnaeus, 1758) (Linnaeus, muscorum Pupilla (Clessin, 1871) (Clessin, alpicola Pupilla Succinea putris Beck,Succinea 1837 (Draparnaud, 1801) oblonga (Draparnaud, Succinella Wehner et al. BMC Ecol Evo (2021) 21:15 Page 12 of 23 Soil moisture Neutral "Low" Neutral Neutral "Low" "High" Neutral Neutral "High" Neutral Neutral Neutral Mid-specialist pH Neutral "High" Mid-specialist "High" Neutral Neutral Neutral "High" Neutral Neutral Neutral Neutral Neutral Fertilization Neutral Neutral Neutral Neutral Neutral Neutral Neutral Loser Neutral Neutral Neutral Neutral Neutral Mowing Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Grazing Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral Neutral LUI Neutral Loser Neutral Neutral Neutral Neutral Neutral Neutral Loser Neutral Loser Neutral Loser Total abundance Total 1 14 493 63 1829 3456 47 102 355 2 8 2 16 Occurrence 1 4 40 5 106 96 9 12 69 1 5 2 10 Region A AH AHS AS AHS AHS S AS AHS S AH H AHS RedList V 3 * 1 * * 3 V * 3 * G * (continued) 4 Table in bold given are values Signifcant and fertilization intensity mowing grazing, (LUI), land-use index land-use parameters the following loser or mid-specialist to as winner, assigned Species are 1 = critically endangered, V = near threatened, unknown to R = very extent, G = endangered risk rare, (least concern), * = no current Red List status: respectively. species, and high-gradient low- to refer “high” and “Low” 3 = vulnerable 2 = endangered, Species (C. Pfeifer, 1828) Pfeifer, striolatus (C. Trochulus (A. Férussac, 1807) Férussac, (A. cylindrica Truncatellina (O.F. Müller, 1774) Müller, (O.F. costata Vallonia (Gredler, 1856) enniensis (Gredler, Vallonia Sterki, 1893 excentrica Vallonia (O.F. Müller, 1774) Müller, pulchella (O.F. Vallonia Jefreys, 1830 Vertigo angustior Jefreys, Vertigo antivertigo 1801) (Draparnaud, (Draparnaud, 1801) (Draparnaud, Vertigo pygmaea Vertigo substriata (Jefreys, 1833) (Westerlund, 1871) contracta Vitrea (Studer, 1820) diaphana (Studer, Vitrea (O.F. Müller, 1774) Müller, Vitrina pellucida (O.F. Wehner et al. BMC Ecol Evo (2021) 21:15 Page 13 of 23

a 20 15 10 Fertilization [AWM ] 05

0.0 0.2 0.4 0.60.8 1.0 Percental occurrence in Forest b .5 7. 07 .5 pH [AWM] 6. 06

0.0 0.2 0.4 0.60.8 1.0 Percental occurrence in Forest Fig. 2 Relation between the responses (abundance-weighted mean) of each snail species to fertilization (a) and soil pH (b) and their proportional occurrence in forests. Indicated species above the line are signifcant “winners” for fertilization respective soil pH, indicated species below the line (in italic) are signifcant “losers”

human land use are less frequently discussed. Our previ- unexplained variation may mirror land use. Our results ous study [27] focused on land snail density, diversity and confrmed that land-use intensity signifcantly infuenced species composition and emphasized that direct impacts the trait distribution of snail communities, a pattern that of land use on snail communities were on average lower was more pronounced in forest habitats than in grass- than the impact of abiotic drivers and biotic substrates. lands. Since snail species in forest communities seem to However, unlike several studies on insects, few direct be more specialized than those of grassland communi- efects have been shown for wood harvesting in forests ties [12, 28], they may sufer more from habitat changes. and mowing in grasslands on snail diversity [27]. How For example, as the activity level of snails is temperature- these direct land-use efects infuence populations of sin- dependent, thinning the canopy by wood harvesting or gle species and whether these efects are related to spe- a high amount of non-native trees can enhance solar cies-specifc traits remains largely unclear. irradiance and the enhanced snail locomotion allows Our study showed that snail assemblages varied con- the exploitation of ambient heterogeneity [29] and may sistently in their trait composition (shell size, number favor species with higher light preferences. Tis hypoth- of ofspring, light and humidity preference, drought esis is consistent with results from snail assemblages in resistance and inundation tolerance) across regions and our study, since the community-weighted mean (CWM) among the two habitats, forests and grasslands. Te vari- of light preference increased with the amount of non- ation between regions is consistent with a biogeographic native, mainly coniferous trees that may not have a closed gradient of increasing land snail diversity from the north canopy. Furthermore, changes of the community trait to south caused by historical and ecological factors (tem- composition are not only directly caused by land-use perature, moisture) [12, 22] and snail species responded parameters, but also by indirectly changing abiotic fac- diferently to variable physical environments [13]. Local tors such as soil pH and soil moisture although most snail environmental conditions have been shown to explain species exhibit broad niches for these abiotic factors. about 19% of the trait variability of a snail metacommu- In our study, 4% of all forest and 21% of all grassland nity in Sweden [17], where the authors suggested that the snail species were signifcant losers concerning the Wehner et al. BMC Ecol Evo (2021) 21:15 Page 14 of 23

Acanthinula aculeata Monarchacartusiana Trochulus hispidus Vertigosubstriata

Urticola umbrosus Vitrea contracta Aegopinella nitens (69.2%) Nesovitrea hammonis Vallonia costata (1%) Vitrina pellucida Aegopinella pura (30.8%) Nesovitrea petronella Vallonia costata Zonitoides nitidus Carychium minimum (99%) Pseudotrichia rubiginosa Vallonia enniensis (1.8%) Carychium tridentatum (1%) Punctum pygmaeum Vallonia excentrica (7.8%) Ceciliodesacicula Pupilla muscorum Vallonia pulchella (89.4%) Clausilia bidentata

Pupilla alpicola Cochlicopa lubrica Vertigo angustior (13.5%)

Discus rotundatus Succinea putris Vertigo antivertigo (29,4%)

Euconulus fulvus Vertigo pygmaea (57.2%) Succinella oblonga Schorfheide-Chorin

Acanthinula aculeata Cepaea nemoralis Monarcha cartusiana Trochulus sericeus (20%)

Clausilia bidentata Monachoides incarnatus Truncatellinacylindrica Aegopinella nitens (10.8%) Vallonia costata (12.3%) Cochlicopa lubrica Nesovitrea hammonis Aegopinella nitidula (6,7%)

Vallonia excentrica (74.2%) Cochlodina laminata Oxychilus cellarius Aegopinella pura (82.5%)

Discus rotundatus Oxychilus draparnaudi Ariantaarbustorum Vallonia pulchella (13.5%) Platylapolita Candidula unifasciata Ena montana Vertigo pygmaea Punctum pygmaeum Carychium minimum (5.3%) Euconulus fulvus Vitrea contracta (35.7%)

Pupilla muscorum Carychium tridentatum (94.7%) Helicella itala Vitrea crystallina (18.7%)

Ceciliodesacicula Succinella oblonga Helicodonata obvoluta Vitrea diaphana (46.2%)

Cepaea hortensis Helix pomatia Trochulus hispidus (80%) Vitrinapellucida Hainich-Dün

Acanthinula aculeata Cepaea hortensis Nesovitrea hammonis Vallonia costata (26%) Cochlicopa lubrica Aegopinella nitens (25.2%) Oxychilus draparnaudi Vallonia enniensis (0.3%)

Cochlodina laminata Aegopinella nitidula (1.2%) Platylapolita Vallonia excentrica (36%) Discus rotundatus Punctum pygmaeum Aegopinella pura (73.5%) Vallonia pulchella (37.8%) Ena montana Pupilla muscorum

Ariantaarbustorum Vertigo angustior (1.5%) Euconulus fulvus Succinella oblonga Vertigo antivertigo (1%) Candidula unifasciata Euomphalia strigella Trochulus hispidus (54.7%) Vertigo pygmaea (97.6%) Carychium minimum (18.7%) Helicella itala Trochulus sericeus (18.5%) Vitrea contracta (79.3%)

Carychium tridentatum (81.3%) Helicodonta obvoluta Trochulus striolatus (26.8%) Vitrea crystallina (20.7%)

Ceciliodes acicula Monachoides incarnatus Truncatellinacylindrica Vitrinapellucida SwabianAlb

Fig. 3 Proportional distribution of land snail species in the Schorfheide-Chorin, the Hainich-Dün and the Swabian Alb. Grasslands are given in light grey, forests in dark grey. The three most abundant species are symbolized by big circles, less abundant species by small circles. Species that are underlined are specifc for the respective region. Percentages in brackets indicate the proportional occurrence of species of the same genus Wehner et al. BMC Ecol Evo (2021) 21:15 Page 15 of 23

Table 5 Statistical p values of a general linearized model with Poisson distribution testing the infuence of land-use parameters and abiotic factors on species vulnerability Species vulnerability Estimate p value Species vulnerability Estimate p value

FORMI 0.224 0.689 LUI 0.511 0.256 − − Occurrence 1.441 0.002 Occurrence 1.303 < 0.001 − − Total abundance 0.546 0.158 Total abundance 0.673 0.001 Inonat 0.424 0.150 Mowing 0.031 0.903 − − Occurrence 1.512 0.002 Occurrence 1.227 < 0.001 − − Total abundance 0.598 0.112 Total abundance 0.638 0.001 Idwcut 0.094 0.945 Grazing 0.049 0.339 − − Occurrence 1.454 0.005 Occurrence 1.212 < 0.001 − − Total abundance 0.573 0.177 Total abundance 0.643 < 0.001 Iharv 0.119 0.948 Fertilization 0.038 0.413 − Occurrence 1.477 0.002 Occurrence 1.224 < 0.001 − − Total abundance 0.594 0.103 Total abundance 0.616 0.001 pH 0.198 0.573 pH 0.092 0.849 Occurrence 1.643 0.004 Occurrence 2.001 < 0.001 − − Total abundance 0.699 0.104 Total abundance 0.615 0.012 Soil moisture 0.039 0.333 Soil moisture 0.043 0.330 − Occurrence 1.719 0.002 Occurrence 1.184 < 0.001 − − Total abundance 0.726 0.063 Total abundance 0.631 0.001

Signifcant values are given in bold

a 4 y 123 Species vulnerabilit 0

1.00 1.05 1.10 1.15 1.20 1.25 5−dimensional niche volume (forest) b 4 Species vulnerability 0123

050100 150 5−dimensional niche volume (grassland) Fig. 4 Species vulnerability in relation to the fve-dimensional niche hypervolume in forest (a) and grassland (b). The hypervolume was the product of the abundance-weighted standard deviations (AWSDs) of all single land-use components as well as pH and soil moisture in forests or grasslands, respectively Wehner et al. BMC Ecol Evo (2021) 21:15 Page 16 of 23

compound indices of land-use intensity, including three habitat loss and climate change due to synergistic efects land-use components in the forests or in the grasslands, of a narrow niche and a small range size. respectively. Te proportion of losers among grassland Only a few snails in our study across managed forests snail species was lower than the level found for grass- and grasslands are considered threatened or endangered hoppers (about 52%) [30] and plant- and leafhoppers according to the national Red List. Consistent with the (about 34%) [9], but similar to that for moths (28%) expectation based on their environmental niche breadth, [31], confrming that snails are a suitable indicator for the species’ vulnerability status was signifcantly pre- habitat quality and land-use intensity [17, 22, 32, 33]. dicted by a particularly narrow niche hypervolume—an Te low proportion of loser species may be explained index that includes single land-use components as well by their ground-living behavior (intangible for combine as pH and soil moisture in each habitat. Te smaller the harvesters), the presence of a shell (protection against hypervolume of a species, the higher its vulnerability exposure and predation) and a larger diet breath com- according to the Red List. In addition, rarity was impor- pared to insect taxa (omnivory for fexibly changing tant: in forests, the most important predictor for their food resources). However, we may have underestimated vulnerable status was a low number of sites in which the amount of loser species since we did not distinguish they occurred. In grasslands, both their restricted occur- between living individuals and empty shells. Empty shells rence and low total abundance predicted the species’ decay at diferent rates under diferent ecological condi- vulnerability. tions [44]. Terefore, in some cases we may have evalu- ated shells of species which can no longer be found alive Conclusion in the respective places. Keeping this in mind, our meth- In summary, our results indicate that the trait composi- odological approach may have ramifcations on the con- tion of snail communities was signifcantly altered by clusions drawn. land-use intensities and abiotic conditions, and several While increasing land-use intensity in open habitats is species especially in grasslands were losers of intensive known to trigger a decline of pollinator species, and such land use. Tese land-use and environmental responses losses were associated with species-specifc trait attrib- were largely independent of specifc traits and the spe- utes such as a narrow diet breadth, climate specialization, cies’ Red List status—this suggests that complementary a large body-size and low fecundity [33–39], we did not risks may be important for predicting a species’ vulner- fnd traits for snail species to correspond with their land- ability. Instead, species vulnerability was mirrored in the use response at species level. Tis is surprising, given species’ rarity and its overall niche hypervolume includ- that particularly those traits that are associated with soil ing single land-use components and abiotic factors. moisture (drought resistance, inundation tolerance), body size or reproductive outcome are likely to respond Methods to human-mediated disturbances. Furthermore, land-use Data origin efects in forests were independent of the species habitat Data for this study were already part of a previous analysis association (i.e. forests specialists were equally afected as of biodiversity and community composition, i.e. Wehner non-forests specialists), but grassland specialists sufered et al. [27] and are available at https​://www.bexis​.uni-jena. more from land use (i.e. fertilization) and were more de/Publi​cData​/Publi​cData​Set.aspx?Datas​etId=24986​ dependent on high soil pH. . Wehner et al. [27] collected 15,607 snail individu- Note that single land-use parameters and abiotic con- als belonging to 71 taxa in three regions in Germany in ditions are often confounded in real landscapes as in our the framework of the Biodiversity Exploratories Project study, and thus responses of some snail species may not (http://www.biodi​versi​ty-explo​rator​ies.de) [2]. Te col- always correspond to single environmental dimensions laborative research unit addresses efects of land-use on as known from their global distribution or other sources. biodiversity and biodiversity-related ecosystem processes For example, Cochlicopa lubricella is a xerophilic land in three regions: the Swabian Alb (ALB), a low-moun- snail [42] whereas our data showed a neutral response to tain range in South-West Germany (460–860 m a.s.l., soil moisture. 09° 10′ 49″–09° 35′ 54″ E/48° 20′ 28″–48° 32′ 02″ N), the Hainich-Dün (HAI), a hilly region in Central Germany (285–550 m a.s.l., 10° 10′24″–10° 46′ 45″ E/50° 56′ 14″– Species’ vulnerability 51° 22′ 43″ N) and the Schorfheide-chorin (SCH), a gla- Te range of resources and the ecological conditions cial formed landscape in North-East Germany (3–140 m generally defne the niche breadth and determine the a.s.l., 13° 23′ 27″–14° 08′ 53″ E/52° 47′ 25″–53° 13′ 26″ geographical area of a species at the small or large scale N). SCH is characterized by the lowest annual precipi- [40]. Specialists are expected to be more vulnerable to tation (520–580 mm), with a mean annual temperature Wehner et al. BMC Ecol Evo (2021) 21:15 Page 17 of 23

of 6–7 °C. It is followed by HAI (630–800 mm, 6.5–8 °C) common practice, although some traits, e.g. shell size and and ALB (800–930 mm, 8–8.5 °C). number of ofspring, may be correlated, see [17]). In each region, 100 experimental plots (50 in forests For comparing snail communities among habitats and and 50 in grasslands) were setup in 2008 along a land- regions, the community weighted mean (CWM) of each use gradient covering diferent management types and trait was calculated as CWM per plot p intensities including mowing, grazing and fertilization I a , in grasslands and the proportion of non-native trees, the CWM = T • i p p i A proportion of dead-wood with saw cuts and the propor- i=1 p tion of wood harvested in forests (Table 6). Forest plots have a size of 1 ha and grassland plots are 0.5 ha in size. where Ti is the trait value of species i, ai,p is the abun- In June 2017, Wehner et al. [27] took fve replicated dance of species i in plot p and Ap the total abundance of surface samples from all 50 forest and 50 grassland exper- all snails in plot p (total I species). imental plots (EPs) in the Swabian Alb and the Hainich, and from 49 forest and 34 grassland plots in the Schorf- Environmental niches heide due to constrained accessibility (1415 samples in We characterized the environmental conditions of each total). Shelled snails were subsequently determined to forest or grassland plot by its land-use intensity and two the species, genus or family level using [41–43]. Although abiotic soil parameters (pH and soil moisture; Table 6) suggested elsewhere [e.g., 44], [27] did not distinguish [52, 53]. Data were obtained from the BExIS database between empty shells and living snail individuals. (Table 6). As our current study focuses on species-level responses, We tested the response of the CWM of each trait only those individuals that could be assigned to the spe- to variation in environmental conditions using linear cies level were used (ALB grasslands: 36, ALB forests: regressions. Values for grazing and fertilization were 37, HAI grassland: 31, HAI forest: 35, SCH grassland: 24, square root transformed before statistical analyses. SCH forest: 21, 61 diferent land snail species in total). In order to characterize the snail species’ responses to Grassland plots (although not permanently fooded) in environmental conditions (land-use gradient, soil condi- one region (Schorfheide) harbored large numbers of tions), we calculated each species’ “environmental niche”. aquatic and semi-aquatic snails. In contrast to our pre- Te method has been established in the context of the vious analysis that covered all snails recorded [27], we Biodiversity Exploratories and was applied to several taxa excluded aquatic snails from the analyses since their role such as grasshoppers [30], cicadas, moths [31], bumble- and responses to terrestrial environmental variables such bees [54] or plants [55]. Te “niche optimum” was cal- as land-use in grasslands remain unclear, culated as the abundance weighted mean (AWM) for species i as

Statistical analyses np a , All statistical analyses were performed in R 3.5.2 [45] AWM = L • i p i p A using the main packages “car” [46], “dplyr” [47], “lme4” p=1 i [48] and “SMDTools” [49]. where np is the number of plots investigated, Lp is the Trait composition of snail communities land-use gradient value of plot p, ai,p the abundance of Morphological and life-history trait values for all snail species i in plot p and Ai the total abundance of species i species were obtained from an established trait data- across all 149 forest or 134 grasslands sites, respectively. base by Falkner et al. [50] and compared to fndings of Hence, the CWM characterizes the plots by the trait dis- [51] whenever possible; see Astor et al. [17] for a similar tribution of snails, and the AWM characterizes snail spe- approach based on [50]. Traits for the set of species in our cies by the environmental conditions of the plot, and the study are summarized in Table 7. Note that these traits snail abundance ai,p is used to weight either species or are either continuous variables (size), integers (ofspring) plot, respectively. or ranks (all others); ranks can been treated as integers or In addition to the AWM as a niche optimum, we also continuous variables for an analysis based on community characterized the “niche breadth” of each species to a weighted mean (CWM, see below); the resulting distribu- single environmental variable using the abundance- tion of the CWM in species-rich communities and across weighted standard deviation (AWSD) [30]. To test a large number of plots typically approach a Gaussian whether AWMs and AWSDs statistically deviate from distribution. Moreover, to explore the response to poten- an expected random distribution, we compared the cal- tial environmental fltering, traits with diferent meaning culated values against the expected values obtained from are treated independently for the following analysis (a a null model that distributes each species across Ni sites Wehner et al. BMC Ecol Evo (2021) 21:15 Page 18 of 23 Mean of 2015/2016 Year used Year Mean 2017 2017 2017 2017 2017 Mean of 2015/2016 Mean of 2015/2016 Mean of 2015/2016 Ammer Jürgen Bauhus Ammer Jürgen Katrin Lorenzen Source/owner Ingo Schöning Theresa KlotzingTheresa Peter Schall Christian Peter Markus Fischer Juliane Vogt Juliane Markus Fischer Wolfgang Weisser Wolfgang Ayasse Manfred 19266 version 1.15.12 19266 version Dataset ID Dataset 22246 Verion 22246 Verion 1.1.9 24646 version 1.2.8 24646 version al. 2012 [ 41 ] Blüthgen et al. References Kahl and Bauhus 2014 [ 40 ] Kahl and Bauhus 2014 [ 40 ] Kahl and Bauhus 2014 [ 40 ] Kahl and Bauhus 2014 [ 40 ] al. 2012 [ 41 ] Blüthgen et al. al. 2012 [ 41 ] Blüthgen et al. 2012 [ 41 ] Blüthgen et al. 0–3 Range 3.0–6.7 0–2.82 0–1 0–1 0–1 0.53–4.52 0–851 0–433 − 1 ­ year − 1 × − 1 ­ year ­ ha × − 1 ­ ha ing × components taking into account: 1. the proportion of harvested volume, tree 2. the proportion of tree not partspecies that are of community the natural forest and 3. the proportion of dead of saw signs showing wood Each component ranges cuts. of man - between 0 (no sign agement) and 1 (intensive management) harvested tree volume within harvested volume tree by a stand and is estimated of cut stumps the presence as the ratio of and calculated harvested the sum to volume harvestedof standing, and volume dead wood dead wood with saw cuts with saw dead wood amount of dead the total to wood harvested, living and dead of non-natural volume wood - the sum vol species to tree species ume of all tree fertilization plus mowing Each intensities. plus grazing component individual LUI (fertilization, and mowing was standardized grazing) its mean within the to relative model region corresponding - of graz units × days Livestock Frequency per year Frequency Desciption/unit The Formi is the sum of three is the sum of three Formi The Describes the proportion of Represents the proportionRepresents of Estimated as the proportionEstimated of Kg nitrogen × Kg nitrogen index adds compound LUI The Formi saw cuts saw Grazing Mowing Land-use parameter Soil pH Forest management index Forest Proportion of wood harvested of wood Proportion Proportion of dead-wood with of dead-wood Proportion Proportion of non-native trees of non-native Proportion Fertilization Land-use index LUI Description and origin of land-use parameter and abiotic factors Description and origin of land-use parameter Grassland 6 Table Habitat Grassland/forest Forest Wehner et al. BMC Ecol Evo (2021) 21:15 Page 19 of 23 Year used Year Mean May 2017 Source/owner ApostolakisAntonios Susan Trumbore Falk Hänsel Falk Wöllauer Stephan Nauss Thomas Marion Schrumpf Dataset ID Dataset Climate tool Climate Weather station Weather References Range 8.55–55.22 - of the volumem percentage etric content water Desciption/unit Soil moisture in 10 cm depth, as Soil moisture Land-use parameter Soil moisture (continued) 6 Table Habitat Wehner et al. BMC Ecol Evo (2021) 21:15 Page 20 of 23

Table 7 Characterization of snail traits according to Falkner et al. 2001 [50] Trait Explanation Unity

Shell size Maximal height of an oblong shell or the maximal diameter of a depressed shell in mm mm; in case of globose/conical shells, whichever measure has the greater value is considered Number of ofspring Numbers of eggs/juveniles per clutch 1–10, 11–100, > 100 Light preference Degree to which species occur in direct sunlight or shaded conditions Deep shade, light shade, no shade, indiferent Humidity preference Degree to which species occur at wet or dry conditions Wet, moist and dry Drought resistance Degree to which species can survive dry periods Hours, days, weeks, months Inundation tolerance Degree to which species are tolerant to inundation Low, moderate, high

Species vulnerability with the same probability, with Ni being the number of sites in which species i was found. Te null model thus Vulnerability (classifed as a rank variable comparable to chooses values of the focal land-use parameter (LUI, IUCN categories: least concern, endangered to unknown Formi, single components, pH, soil moisture) of Ni sites extent, very rare, near threatened, critically endan- and calculates a distribution of predicted AWMs and gered, endangered, vulnerable) of land snail species was AWSDs values for each species based on 10,000 itera- obtained from the Red List 2011 (according to [56]; see tions. Te null model was restricted to the one, two, or Table 3). We tested the relation of vulnerability with the three regions in which the species was recorded to con- species’ habitat association by calculating the propor- sider potential distribution boundaries of each species in tional occurrence in either forest or grassland habitats Germany that may not be related to plot conditions [30]. of a certain species’ presence; a ‘specialist’ was defned if As in any randomization model, the proportion of more than 90% of all individuals found were present in AWMs or AWSDs from 10,000 null models with greater one habitat (forest or grassland). Te relation between or smaller expected values respectively than the observed vulnerability and species’ habitat association was tested value, provides the p value for the signifcance of the devi- by a linear model using the land-use management com- ation between observed and expected values. A ‘winner’ ponents and the abiotic conditions as fxed factors and is defned as a species with an observed AWM larger than the proportional occurrence as explanatory factor. the upper 5% of the distribution of AWMs obtained by To further test if a species’ vulnerability can be pre- the null models (i.e. adapted on higher-than average land- dicted by its land-use response (‘winner’ or ‘loser’ status) use intensity), a ‘loser’ shows an observed AWM smaller and its relation to abiotic soil conditions, we used a gen- than the lower 5% (low land-use intensity specialist). For eral linearized model with Poisson distribution includ- species which could be classifed neither as ‘losers’ nor ing vulnerability as response factor and the respective as ‘winners’, we tested whether they are specialized on land-use parameter or abiotic factor, the number of plots intermediate land-use or abiotic levels, that is, whether where the species occurred and its total abundance as they have an intermediate AWM with a narrower niche explanatory factors. Values for grazing and fertilization than expected. We standardized the niche breadth as were square-root transformed prior to statistical analyses weighted coefcient of variation (CV = AWSD/AWM) and data on abundances and occurrence were log trans- to account for the increase in SD with increasing mean, formed because of data structure. and compared observed CV and expected CV from the Finally, we calculated a fve-dimensional niche hyper- null models. Tis comparison allows us to distinguish volume (consistent with Hutchinson’s n‐dimensional ‘opportunists’ (observed CV ≥ expected CV) from spe- niche concept) as a proxy for the total ‘niche breadth’ cies that are ‘specialized’ on intermediate land-use of each snail species by multiplying the abundance- intensities (observed CV < expected CV and species not weighted standard deviations (AWSD) of all three single only occurring on one site, i.e., CV ≠ 0) [30]. Te envi- land-use components as well as of pH and soil moisture, ronmental niche (AWM, AWSD) and the assignment of respectively. Te hypervolume was defned for forests low- and high-gradient specialists were also calculated and grasslands separately. for soil pH and soil moisture, although we did not adopt Whether the total niche breadth can predict vulner- the ‘loser’/’winner’ terminology here unlike for land-use ability was tested using a Spearman rank correlation intensity. between the vulnerability and the fve-dimensional niche hypervolume. Wehner et al. BMC Ecol Evo (2021) 21:15 Page 21 of 23

Supplementary Information Additional fle 12: Appendix 12. Infuence of the abundance-weighted The online version contains supplementary material available at https​://doi. mean (AWM) of soil pH on the maximum shell size, number of ofspring, org/10.1186/s1286​2-020-01741​-1. light preference, humidity preference, drought resistance and inundation tolerance in grasslands. Species in italics are land-use “winners”, species in bold are land-use “losers”. Additional fle 1: Appendix 1. Summary of signifcant efects of land-use parameters and abiotic factors in forests (forest management index Formi, Additional fle 13: Appendix 13. Infuence of the abundance-weighted proportion of non-native tress, proportion of dead wood with saw cuts, mean (AWM) of soil moisture on the maximum shell size, number of proportion of wood harvested, pH and soil moisture) and grasslands ofspring, light preference, humidity preference, drought resistance and (land-use index LUI, mowing, grazing, fertilization, pH and soil moisture) inundation tolerance in grasslands. Species in italics are land-use “winners”, on the community weighted mean of the maximum shell size, the num- species in bold are land-use “losers”. ber of ofspring, light preference, humidity preference, drought resistance Additional fle 14: Appendix 14. Relation of the abundance-weighted and inundation tolerance. * p < 0.05, ** p < 0.01, *** p < 0.001. negative means (AWM) of the forest management index, proportion of non-native efect, positive efect. ↓ ↑ trees, proportion of dead wood with saw cuts, proportion of wood har- Additional fle 2: Appendix 2. Infuence of the abundance-weighted vested, pH and soil moisture and the proportional occurrence of a certain mean (AWM) of the forest management index on the maximum shell size, species in forests. number of ofspring, light preference, humidity preference, drought resist- Additional fle 15: Appendix 15. Relation of the abundance-weighted ance and inundation tolerance in forests. Species in italics are land-use means (AWM) of the land-use intensity, mowing, grazing, fertilization, pH “winners”, species in bold are land-use “losers”. and soil moisture and the proportional occurrence of a certain species in Additional fle 3: Appendix 3. Infuence of the abundance-weighted forests. mean (AWM) of the proportion of non-native trees on the maximum shell size, number of ofspring, light preference, humidity preference, drought resistance and inundation tolerance in forests. Species in italics are land- Acknowledgements use “winners”, species in bold are land-use “losers”. We thank the managers of the three Exploratories, Kirsten Reichel-Jung, Iris Steitz, and Sandra Weithmann, Juliane Vogt, Miriam Teuscher and all former Additional fle 4: Appendix 4. Infuence of the abundance-weighted managers for their work in maintaining the plot and project infrastructure; mean (AWM) of the proportion of deadwood with saw cuts on the Christiane Fischer for giving support through the central ofce, Andreas maximum shell size, number of ofspring, light preference, humidity pref- Ostrowski for managing the central data base, and Markus Fischer, Eduard Lin- erence, drought resistance and inundation tolerance in forests. Species in senmair, Dominik Hessenmöller, Daniel Prati, Ingo Schöning, François Buscot, italics are land-use “winners”, species in bold are land-use “losers”. Ernst-Detlef Schulze, and the late Elisabeth Kalko for their role in setting up the Additional fle 5: Appendix 5. Infuence of the abundance-weighted Biodiversity Exploratories project. Many thanks to all research assistants: Kevin mean (AWM) of the proportion of wood harvested on the maximum shell Frank, Wiebke Kämper, Jessica Schneider, Andrea Hilpert, Matteo Trevisan, size, number of ofspring, light preference, humidity preference, drought Matthias Brandt, Sebastian Schmelzle, Tewannakit Mermagen, Kathrin Ziegler, resistance and inundation tolerance in forests. Species in italics are land- Annika Keil, Andreas Kerner, Katja Gruschwitz, and Kimberly Adam. use “winners”, species in bold are land-use “losers”. Authors’ contributions Additional fle 6: Appendix 6. Infuence of the abundance-weighted KW did the feldwork, collected and determined snail species, performed mean (AWM) of soil pH on the maximum shell size, number of ofspring, the statistical analyses and wrote the manuscript. CR assisted in the species light preference, humidity preference, drought resistance and inundation determination and commented on the manuscript. NKS assisted in the statisti- tolerance in forests. Species in italics are land-use “winners”, species in bold cal analyses and commented on the manuscript. WWW and NB designed are land-use “losers”. the study, NB also assisted in the statistical analyses and the paper writing. All Additional fle 7: Appendix 7. Infuence of the abundance-weighted authors have approved to the fnal version. mean (AWM) of soil moisture on the maximum shell, size number of ofspring, light preference, humidity preference, drought resistance and Funding inundation tolerance in forests. Species in italics are land-use “winners”, Open Access funding enabled and organized by Projekt DEAL. The work has species in bold are land-use “losers”. partly been funded by the DFG Priority Program 1374 “Infrastructure-Biodiver- sity-Exploratories” (DFG BL860/8-3). Additional fle 8: Appendix 8. Infuence of the abundance-weighted mean (AWM) of land-use intensity (LUI) on the maximum shell size, num- Availability of data and materials ber of ofspring, light preference, humidity preference, drought resistance Snail data obtained by [27] and used in this study are available online and inundation tolerance in grasslands. Species in italics are land-use under https​://www.bexis​.uni-jena.de/Publi​cData​/Publi​cData​Set.aspx?Datas​ “winners”, species in bold are land-use “losers”. etId 24986​. Data on snail vulnerability were obtained from the Red List 2011 Additional fle 9: Appendix 9. Infuence of the abundance-weighted according= to [43] and snail traits were extracted from [38]. Environmental data mean (AWM) of mowing on the maximum shell size, number of ofspring, and those for land-use intensity in grasslands and forests were obtained from light preference, humidity preference, drought resistance and inundation the BExIS database (see Table 6). tolerance in grasslands. Species in italics are land-use “winners”, species in bold are land-use “losers”. Ethics approval and consent to participate The study complied the fundamental principles of the Basel declaration for Additional fle 10: Appendix 10. Infuence of the abundance-weighted research in animals. The investigated species are not at risk of extinction. mean (AWM) of grazing on the maximum shell size, number of ofspring, Fieldwork permits were issued by the responsible state environmental ofces light preference, humidity preference, drought resistance and inundation of Baden-Württemberg, Thüringen, and Brandenburg. tolerance in grasslands. Species in italics are land-use “winners”, species in bold are land-use “losers”. Consent for publication Additional fle 11: Appendix 11. Infuence of the abundance-weighted Not applicable. mean (AWM) of fertilization on the maximum shell size, number of ofspring, light preference, humidity preference, drought resistance and Competing interests inundation tolerance in grasslands. Species in italics are land-use “winners”, The authors declare that they have no competing interests. species in bold are land-use “losers”. Wehner et al. BMC Ecol Evo (2021) 21:15 Page 22 of 23

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