SIMILARITY , DIVERSITY AND EQUITABILITY OF SNAIL COMMUNITIES IN LOWER MOUNTAIN ZONE IN THE TATRA MOUNTAINS †

The malacofauna of 24 localities in the lower mountain zone of the Tatra Mts includes 61 species. The richest communities have a high species diversity H’ and a moderate equitability J’. Communities of a lower species diversity H’ and of their equitability J’ similar as that of the former ones inhabit biotopes with limited food and habitat resources. A very low species diversity H’, along with extremely varied values of equitability J’, is characteristic for communities inhabiting biotopes whose conditions are unfavourable for snails. In the discussion on the structural parameters of the snail communities in the Tatra Mts and their qualitative similarity, connections between communities of the same kind appear several times. Qualitatively similar communities show similar structural parameters. A clear structural similarity is marked also when extreme qualitative differences occur. A strong pressure of natural and/or anthropogenous conditions results in the formation of communities of extremely distinct species composition. key woRDs: malacofauna, species diversity H’, equitability J’, synanthropisation, qualitative similarity Folia Malacologica 2/1988 was originally published as No. 1112 of Scientific Bulletins of University of Mining and Metallurgy, Cracow. This digitalised version was prepared by the Association of Polish Malacologists and first published on-line on December 30th, 2016. http://dx.doi.org/10.12657/folmal.002.001 Folia Malacol. 2: 7–28


INTRODUCTION
There is still a quite limited number of malacological studies concerning coenological problems.Before 1950 the mollusc fauna of Poland was investigated mostly from the faunistic or systematic point of view (Riedel 1954,. 1957, Wiktor 1964, 1973).Only a few studies deal with phytosociological characteristics of habitats or analyze relations between particular species and species associations with biotopes (Urbanski 1939, Orozdowski 1963, Ozi~czkowski 1972, 1974, Oyduch 1980).The methods appl~ed are similar to those used in plant sociology (Jungbluth 1975).No method has been found applicable to comparisons of the mollusc communities of physiographically remote regions whose biotop~. in addition, are considerably varied.The paper is an attempt at such an analysis based rather on the structural indexes commonly used in ecology of animal communities (e.g.birds: Glowacinski 1975Glowacinski , 1981) ) than on the species composition.
The present description of snail communities is based on their similarity, species diversity and ~quitability.Its aim is a comparative analysis of the snail communities of the main types of biotopes in the Tatra Mts. and a study of some aspects of both the snail communities formation and factors determining the community structure and function.

MATERIAL AND METHODS
The material was collected in 1982 -1983 in the Tatra National Park.A total of 95 samples from 24 localities were taken.The semi--quantitative method was applied: snails were collected for on equal time-span on each locality (sweeping with entomological net,sieving and sorting litter, collecting under stones, pieces of wood, and bark).The frame-square method has been abandoned mainly due to unfavourable weather conditions (drought) but also due to the high diversification (a mosaic pattern) of habitats, low densities, and dispersion characters: Hence,.the quantitative data are probably biased towards lower values.
The snail communities of the Tatra Mts. were analysed in respect of their species composition, qualitative similarity, species diversity and equitability.The parameters were calculated according to the following formulas~

A + B -2C
A + 8 -c where: dst.-the taxonomical distance between two communities according to Marczewski and Steinhaus (1959) A -the number of species in the first community B the number of species in the second community C -the number of common species for both the communities.The results of Romaniszyn (1972) and Legendre and Legendre (1979) justify the application of this index.where Hf\ax H -the species diversity of a community according to the Shannon -Weaver formula N -the number of individuals in a community ni -the number of the individuals of each species c -3.321928 J -the equitability (evenness) according to Pielou (1975) S -the number of species in a community .
The substratum is a basic factor influencing the microclimate of the biotopes.The limestone, its pH weakly alkaline so favourable, is markedly warmer than the substrata originated f~om a crystalline bedrock and unprefera8le due to their soil reaetion.

RESULTS
The studied snail communities consist of 61 species occurring regularly on the territory of the Tatra National .Park.They are listed in Table 1.The values of t~ ecological paramet~rs analyzed are given in Table 2, and their relations are shown in Figs 1 and 2.
There is no correlation between the diversity (H'J and equitability (J'), the correlation coefficient r = 0,11.Instead of, the points in the diagram showing their relation form three groups (Fig. la).The firsi one is small and covers the communities characterized by the hig~est diversity (H') and a moderate equitability (J').The gro~p comprises the communities of Niznia Kominiarska Glade (loc.4), the Lejowa Valley (lee.5), a lower mountain zone forest between Kalat6wki and Ko"dratowa Glades (lac.17  Similarly, the correlation between the number of species in a community (5) and the equitability (J') is low, r = 0.1109 (fig.lb).Their independence wnich follows from the fo~mula (Pielou 1975) and was confirmed by the experimental results, allows the appiication bf the furthest neighbour method and Ward's method in the grouping of the cam~ munities (the groups of Lanee-Williams-Ward hierarchical methods) (Podolec, ZajQC 1978), The character of the relations between the species diversity and the number of species is differentiated.The close correlation of these values following form the Shannon-Weaver formula has been confirmed (r = 0.812: Fig. 2).
The diagram (Fig. 3) of the taxonomical distance (dst.) was based on the Marczewski-Steinhaus index.The distances be1ween the most similar communities are the only ones taken into account.The similarity coefficients (s = 1-dst.)between Nilnia Kominiarska Glade (loc.4), the 17 • 5 .

A. Relation between indexes H and J
Their correlation is statistically insignificant (r = 0.11).Consequently the or9anization level, as H is often called, is not determined by the equitability (J') of a community.On the other hand, three groups of communities are distinguishable.The habitat conditions concerned are expected to differ in their functioning mechanism.The first community group comprises the communities inhabiting the biotopes which offer to molluscs the especially favourable conditions, i.e.Niznia Kominiarska Glade {loo.4), the Lejowa Valley (lac.5), a forest between Kalat6wki Glade and Kondratowa Glade ( loc.17), and G~sia Szyja Mt.
Cloc. 21) .The species diversity of the communities is high (the highest among the studied communities) and their equitability is mode-r~te.The food crase and carrying capacity of th€ communiti~s are probably so rich and high respectively, that they do not limit the species diversity and the populations of each particular species develop practically independently on the others, According to Thompson (1982) it may suggest that due to the relatively high number of species, none of them dominating, the competition in the communities is not very strong.However, close interactions between pairs cannot be excluded, as a pa~t of the long-term eo-evolution process; hence the equ1tability is moderate.
The second group includes the communities whose species diversity is lower and the equitaDility is similar as in the preceding one.The values of their species diversity vary widely (2.6-3.6) and the diversity increases along with the equitability.).The field observations suggest that this most numerous group i s distinct with an increasing competition caused by the limited food base and the habitat conditions.The rather strong competition results in changes in the community structure and in the differences between the numbers of the particular species.Thus, competition could be a factor determining both the structure and qualltative-quantitative relations in a community.The third group consists of the communities with a very low species diversity and a diversified equitabilit¥.They inhabit extremely unfavourable biotopes.All the biotopes except Giewont Mt.Qoc.13) where such conditions are natural, are semi-natural due to a past and present human impact (glades: Chocholowska -lac. 1, ~alat6wki -loc.l5,Waksmundzka -lac.22, Kopieniec Mt. -loc.23).Their cl.'ystalline substratum and the resulting microclimate conditione, which are unfavourable for malacofauna, along with too intensive grazing : prevent the mollusc communities from reaching a stable structure (i.e.similar to that of the communities inhabiting natural biotopes in the Tatra Mts.).It is probable that on the above localities the populations of each species develop independently on each other.Their ahundances are limited by climatic and/or physico-chemical conditions' and they do not interact between each other in the way described for the preceding group.
The above suggestions to a great extent base on arbitrary statements and field observations.Further malacological and ecological studies might support and explain the observed relationships.
The observations presented above indicate only the existence of three groups of snail communities in the lower mountain habitats of the Tatra Mts.

B. Relation between indexes J'and S
Due to the lack of correlation between the two parameters, following from the J ' formula and evidenced by a low correlation coefficient (r = 0.11), it was possible to group the communities according to the hierarchical methods of Lance -Williams -Ward.The results of the grouping are partly in agreement with the above classification based on the values of H' and J= Two tests were applied here: the furthest neighbour method and Ward's method.The results of the tests group the communities of: Chocholowska Glade (lac.1), Kalat6wki Glade (lac.15), and Giewont Mt. (lac.lJ) (fig.lb).The conclusion is drawn that the effects of the human impact on lac. 1 and lac.• 15 are approximatelly as harmful as the extremely hard habitat conditions on Giewont Mt. (lac.13).However, on the latter locality the influence of a tourist movement on the development of the epilithic grasslands should not be neglected, as the grasslands are the main mollusc habitat there.
Dn the contrary, the communities of Nitnia Knminiarska Glade (lac.4) and the lejowa Valley (lac.5) have a high number of species.The further neighbour method allows to classify them as a distinct group, while ¥ard's method indicates that they should be listed together with the communities of the Mala lQka Valley (loc.11) and GQsia Szyja Mt.(loc.21).However, the former two differ so much from the remaining ones in their species diversity, that the results of the furthest neighbour test should rather be admitted.Among the remaining communities the polarization mentioned in the preceding chapter becomes still more pronounced.The communities of the glades: Waksmundzka (lac.22) and Kopieniec Mt. (lac.24), extremely quantitatively and qualitatively poor, form a distinct group.They differ from those of Giewont Mt. {lac.13), Chocholowska Glade {lac.1), and Kalat6wki Glade (loc.15) in their markedly lower equitability.They may be regarded as a paJo of a large group within which a stea~y increase of the species number ~curs (Fig. lb).This suggests that the low species n~rs in these communities are in a lesser degree related with the human impact than in those of Chocholowska Glade (lac. 1) and Kalat6wki Glade (lac.15).The qualita~ tive impoverishment of the previous communities results mostly from natural, uhfavourable conditions of microclimatic or an~ther character.The remaining 15 communities constitute a distinct, though not very homogenous group within which some subgroups may be discinguished.However, due to the lack of precise measurements of the habitat conoitions, there are po base~ for such a detailed classification.
The above resul~~ show that the number of species in the studied communities doe~ not influence the equitability index that is the highest (ea.0.9) in the habitats • where the human impact is the strongest (loc.1,13,15).The index frequently reaches extreme values at similar species numbers (e.g.Kalat6wki Glade -loc.15, Kopieniec Gladeloc.24).Each of the groups disting~ished in the present paper comprises the communities whose equitability •is similar at approximately the same species number.This indicates their similar structure, i.e. the effect of the habitat conditions and factors determining the population interactions in th~ communities is qualitatively and quantitatively similar.
The high correlation {r = 0.812) of the species diversity and number evidences.the relationship of these parameters, following from the definition of H•.The fact that the correlation coefficient is lower than, for instance, in bird populations (Glowaci~ski 1981), and lower than could be predicted from the formula, indicates the diversified quantitative relations inf~uencing considerably the organization level (H') in the studied communities.

c. rhe qualitative similarity of the communities
The present paper deals, among others, with the mollusc communities of the lower ~ountain glades in the Tetra Mts. which are semi-natural biotopes, as well as with the relations of these biotopes to the natural habitats.Basing on the quantitative similarity an attempt was made to establish: 1. to what degree the malacofauna of such biotopes is determined by the occurrence of the typical species of the natural habitats of the Tatra Mts., 2. whether or not the grazing process results in the formation of the communities by which the semi-natural biotopes can be distinguished as a separate category of habitats.
The similarity of the most similar communities of Ni~nia Kominiarska Glade (loc.4) and the Lejowa Valley (loc.5) is almost self-evident, and may be explained by their close situation and the ecological conditions.Both the communities are surprisingly similar to the malacofauna of G~sia Szyja (loc.21).This locality, slightly ecotonal and peripheral in character (located on the foreland of the crystalline High Tatra Mts.), is considerably drier and situated at a greater altitude.Perhaps the similarity results from the warm calcareous substratum, cooled by winds on GQsia Szyja (lok.21) and by humidity in the lejowa Valley (loc.5) and Niznia Kominiarska Valley (loc.4).Eventually, a complex of microclimatic conditions would arise to promote the development of the quantitatively similar malacofauna.
The small distance separating G~sia Szyja Mt. (lac.21) from the forest between Wierch Poroniec M~. and Goly Wierch Mt. (lac.18) explains the significant similarity of their malacofaunae.The distinct mosai~ -pattern of the latter locality results probably from the fa~t that some species might have come from G~sia Szyja and survive in Piceetum t~ tricum near Goly Wierch.The conditions in the spruce forest are generally unfavourable for snails; only the most resistant species can tolerate brown, acid (pH~5) soil frequented by huMidity falls resulting from the fast flow of surface waters; other soil factors also limit the occurrence of snails in such a forest (Komornicki 1975, Dyduch 1980).
Concerning the long distanc& between Wiktor6wki (lac.19) and the slope between Zahradziska and Przyslop Mi~tusi (lac.7) as well as their different altitudes, the great similarity of the mollusc communities of the localities may be caused by their geobotanical resemblance.
The localities mentioned above are inhabited by the communities whose si~ilarity ~o a! least five other communities is: s 0.4.Also the communities of: Kamienny £leb (lac.3), Przyslop Mi~tusi Glade (loc.10), the Mala l~ka Valley, and some others (Fi.g. 4) belong to this category.
Among the communities showing distinct differences in relation to at least five others, there are five inhabiting glades (their similarity index reaches the values= 0.4 only once if at all).These are: Chocholowska Glade (lac.1), Kondratowa Glade (lac.6), Kalat6wki Glade (lac.15), Waksmundzka Glade (lac, 22), Kopieniec Glade (loc.24).Besides, such a distinct character and specificitv ~ere observed only in the habitats of extremely unf~vourable conditions -natural ones (Przyslop Mi~tusi -lac.8), tho~e caused by man (a rarest along the road Kutnice -Kalat6wki -lac.16), or of both origins (Giewont Mt. -loc.13).The influence of grazing on the five glades mentioned above is strong enough to cause the elimination of almost all the specialized species.Only the tolerant ones as: Arian subfuscus, Cochlicopa lubri-~.Vitrina pellucida survive -a particular species on each glade, depending probably on local habitat conditions.This is why each particular glade (especially those most affected) differs qualitatively from till! others.

D. Relations between qualitative similarity (s), species diversity (H'), and equitability (J')
The relations between the same communities appear several times in the discussion on the structural parameters (H' and J') and the qualitative similarity, as well as in the groupings based on the structural
E. Synanthropization of the malacofauna of the Polish Tatra Mts.
The degree of synanthropization of the studied communities was determined basing on the percentage of ubiquitous (eurytopic) species, whose increase in the Tatra Mts.seems caused .by the human impact.The eurytopic species are: Cochlicopa lubrica, Arian subfuscus, Nesovitrea hammonjs, N. petronella.They occur rather regularly, though never numerously in the natural biotopes of the Tatra Mts.,while in the conditions of a strong human impact their number increases (Dyduch-Falniowska, Fyda in press).
Among the studied communities there are some whose low diversity is caused by other factors than man-caused changes.Their low values of species number and diversity result from the natural conditions, unfavourable for malacofauna (lac.B, 9, 13,19,22,24).
The communities of a rather high diversity (H' 3) and with a moderate percentage of ubiquitous species ( 15~) are related with the optimum natural lower mountain biotopes, whose conditions are apparently the best for most snails of the Tatra Mts.
The communities with the highest level of synanthropization (the percentage of eurytopic species 25%) are the most endangered group.On Nitnia Kominiarska Glade (loc.4) in spite of grazing and the high percentage of eurytopic species, the diversity is rather high due to the exceptionally favourable habitat and the topographic conditions.The complex of microclimatic and physico-chemical conditions on Kondratowa Glade (loc.6) is naturally not favourable for molluscs, and the high degree of synanthropization must have resulted from the former grazing.Also the characters of the snail dispersion verify this; snails were found mainly near hut ruins etc.The ~ades: Chocholowska (loc.1), Kalat6wki (loc.15), and Rusinowa (loc.20) are inhabited by the communities of the most disturbed structure.On ChocholQwska Glade (loc. 1) a very high synanthropization level (58~), low div ~rsity and high equitability indicate an advanced process of degradation in the co~munity.The human impact seems the main factor determining the qualitative-quantitative structure of these communities.It is probable, that grazing directly prevents the development of the populations into a pattern in which the community structure is significantly influenced by the food and habitat competition.Other results of grazing are observable in the limited mosaic-pattern and an increase of water flow.The latter is an effect of the re-arrangement of stones and boulders, which previously were rather regularly scattered, and now are arranged in long prisms, parallel to the slope.Consequently, a quantitative impoverishment of the boulderless patches, while compared with those with boulders, is even observable with semi-quantitative methods.The changes caused by grazing eliminate all the more se~sitive species, whereas the remaining ones take approximately good chances to develop themselves.The level of the grazing impact is comparable with the ext~emely unfavourable climatic conditions on the Giewont Mt. (lac.13) .• It is reflected in the diagram (Fig. 4) by tbe distance separating Chocholowska Glade (lac. 1) from the Chocholowska Valley (lac.2): s = 0. ~.The situation on Kalat6wki Glade (lac.15) is similarly bad.At the :slightly lower synanthropization level the inconsistency of the equitability (J'= 0.95) and the diversity (H'= 1.6) indicates that the community is ~ .much more destroyed than the previous one.It is probably c ~nnected with the humidity conditions, which are worse here than on Chocholowska Glade (loc.1).
The Glade Jaworzyna Rusinowa (loc.20), in spite of its high ~ynan thropization level, is characterized by a favourable combination of the studied parameters.However, the presence of all the four species, whose number increase indicates synanthropization, is •notewbrtby.In the conditions of a livestock farming a semi-natural community has forme•d, with a rather high species number (5 = 21), a relatively high diversity (H' = 3.6) and a moderate equitability (J' = 0.82).
The influence of the synanthropization of the malacofauna on the values of ecological structural parameters is various.The .species number 5 and the species diversity H' are not correlated with the degree of synanthropization, whose correlation coefficient with 5: r = 0.14, , with H': r = 0.23, while its correlation with the equitability J' is significant (r = 0.56).
Since• the values compared, i.e. the synanthropization degree and the remaining parameters, are independent as regards their calculation, the latter correlation value suggests that the quantitative inOi'ease of the eurytopic species (resulting from synanthropization) brings about the increase of J•.A gradual increase of the J value was observed in the range of 2 -14% of eurytopic species.It is attributable to the destabilizing tendency of the community, as the index reaches higher values in the communities of the disturbed ecological equilibrium, when the habitat conditions chang~ due to natural (succession) or man-caused fact.ors.In extreme caseSJ the impact is as stron_g as to determine, instead of the natural food and habitat competition, the community organization and, consequently, its structure {Dyduch-Falniowska, Fyda in press).In such a case the percentage of the synanth.ropization-ind.ica-tiVe-species reaches c.a 50% (Fig. 5).I.The quantitatively and qualitatively richest ones inhabit the most favourable for malacofauna biotopes; their diversity H' is high, and the equitability J' -moderat~.11.The communities of the diversity H' lower and equitability J' similar to those of the first group inhabit the biotopes with limited food and habitat resources.Hence, each population of this kind can only develop to a.certain limited degree.Competition in such a community is sharper in comparison with the preceding type, and it is probably the factor determining the structure and quantitative-qualitative relations in the community.Ill.A very low species diversity H' along with the equitability J' reaching the extremely varied values is characteristic of the communities which inhabit the biotopes, whose conditions are unfavourable for snails.It is possible that in some extreme cases (low H', high J') the populations develop independently on each other, with no inter-population interactions; their abundance is limited by the climatic or other physico-chemical factors.The above remarks agree with the results of the grouping .based on the equitability J' and the species number 5 (Fig. 1).

B. The qualitative similarity
The great qualitative similarity of the malacofaunae of Nitnia Kominiarska Glade (loc.4) and the Lejowa Valley (lee.5) can be attributed to the very close situation of the localities, and to their similar habitat conditions.The short distance separating the two malacofaunae from that of G~sia Szyja (loc.21) is surprising.The latter locality of a somewhat ecotonal character resulting from its situation on the foreland of the High Tatra Mts. is considerably drier and located at a higher altitude (1450 m a,s.l.).The locality differs much from the preceding two in its ecological conditions.
The communities inhabiting the intensely grazed glades and/or remaining under a strong pressure of unfavourable natural conditions a~e of a distinct character.The most strongly affected glades differ immensely from the rest in the qualitative respect; their similarity index in relation to any other community frequently does not reach 0.4 (Fig. 4).C. Relations between the structural and qualitative similarity In the discuss!on on the structural parameters of the snail communities in the Tatra Mts. and the qualitative similarity of the communities, associations between the communities of the same group appear several times.The qualitatively similar communities show similar structural param~ters.This concerns, for instance, G~sia Szyja (loc.21), the Lejowa Valley (loc.5) and Nitnia Kominiarska Glade (loc.4).
~ clear s t ructural resemblance may also occur along with extreme qualitative differences.Chocholowska Glade (loc .1) and Giewont Mt. (loc.13) are examples.A strong impact of natural and/or man-caused factors results in the formation of the communities which are extremely distinct in respect of their species composition.One can suppose that in natural communities such an impact causes a common type of structural changes, that gradually lead to the formation of the systems, which structurally resemble each other, but differ extremely in their species composition.Further detailed studies on both the categories of snail communities in the Tatra Mts.seem necessary.Both the structural and temporal aspects should be considered.

D. The effect of synanthropization on the structural parameters
It is obvious that the increase of the percentage of some species (C.lubrica, A. subfuscus, N. hammonis, N. petronella) resulting from the man-caused changes of a habitat, leads to the receding of some others (e.g.Clausiliidae), i.e ., to the qualitative changes of a community.It is difficult to decide whether the species originally inhabiting a given area were eliminated, or receded for some other reasons.The changes have various influence on the values of the ecological structural parameters.Equitability J' appears much influenceable, as its value increases within the range of 2 to 14% of the eurytopic species mentioned above (Fig. 5) .It is attributable to the destabilization tendency of the community.

LIST OF THE SPECIES RECORDED IN THE STUDIED LOCALITIES
Research Centre for the Protection of Nature and Natural Resources, ul.Ariartska 1, 31-512 Krak6w.

No
I!I.Str1kingly mosaic-pattern bottoms of valleys, limestones, slopes, coulatrs (steep mountain gullies) .Since the character of the localities is diversified, floristic remarks are given below.loc. 2. The Chocho!owska Valley, overgrown mostly with Piceetum tatricum.Limestones covered with epilithic grasslands were stupied with a particular attention, The bottom of the valley is covered.with fluvial sands and gravels as well as with lacustrine sediments, 14e latter increases gradually from 0.6 to 0.85.Tnus, the group is somewhat polarized.One pole are the communities from the habitats which are unfavourable in respect of their climate resulting from the situation (Kondratowa Gladelac.6,Przyslop Mi~tusi and Mala t~ka Valley -lac.'•Wiktor6wki lac.19,Wielki Kopieniec -lac.23).The second one are the communities from the richer and quite climatically favourable habitats (e.g .Chocholowska Valley -lac .2,Przyslop Mi~tusi -lac.10, a forest on Kalacki Uplaz -lac.14 • ... . . ....

Table 2
Number of species S, species diversity H' and equitab1lity J'of the malacofauna of studied localities IPrzyslop Mi~tusi Glade