Memoranda Soc. Fauna Flora Fennica 86:28–33. 2010 Community Analysis of the Land Snail (Gastropoda) on the island of Ruissalo, SW Finland Irene Routio Zoological Museum, University of Turku, FI-20014 Turku, Finland In the present analysis, I will examine concomitant species in designated sample areas as well as -type the number and relations of the land snail species in five deciduous-type fo- rests. I will use the land snail populations on the island of Ruissalo (co-ord. 671:323) in Turku, SW Finland as the data for my analysis. 1. Methods eas. Cochlicopa lubrica followed with 67 and Euconulus fulvus in 59 samples. The most com- The samples (Routio 1991, 1993, 1994, 1998, mon snail as regards the number of specimens was 2003, 2004, 2007) were taken on Ruissalo be- Zonitoides nitidus, occurring in 15 sample areas. tween the years 1991 and 2009, 102 of which were Only one species occurred in three samples: taken in forests (Table1). There are 72 samples Zonitoides nitidus, Nesovitrea hammonis and from deciduous forests. Table 2 depicts the type of Succinea putris. biotope the species needs for its habitat and mutual The species mentioned first has an occurrence relationships among the species. correlation of 100–99% as compared to the latter: A total of 1,725 liters of forest debris and soil V.pul / C.lub, V. c o s / C.lub, V.pus / N.ham, C.lam / were analyzed. Samples of the forest debris were N.ham, E.str / N.ham, A.nit / C.lub and N.pet / taken using the same method every year. They N.ham. were evenly gathered from an area, with a radius of In Table 1, you can see that a 93–90% occur- 3 meters, vertically to a depth of 0–5 cm. The sur- rence correlation is: V. s u b / C.lub, Z.nit / E.ful, face soil and the debris were sieved and the snails E.str / C.bid, V.pus / C.lub, V.pus / P.pyg, V.pus / were picked from the sieved material with a fine C.bid. There is also an extremely clear correlation brush. compared to the latter: C.ede / F. fr u (83%), F. fr u / V. p e l (68%), Z.nit / S.put (47%), F. fr u / T. h is (77%), V.pul / V. s u b (73%) and C.lam / V.pus 2. Concomitant species in sample areas (43%). However, it is very rare that N.ham / Z.nit Comparisons between land snail communities can (8%), C.bid / Z.nit (9%), Z.nit / C.asp (7%), V. p e l / be made by examining the place a sample was C.ede (9%), V. p e l / V.pul (9%) and V. s u b / V.pus taken without comparing biotopes and by compar- (7%) occur together with the firstly mentioned in ing the occurrence of a species in the company of the same small biotopes. For example, no occur- another, i.e. the correlation of occurrence in the rences of C.ede / Z.nit, V.pus / Z.nit, T.his / Z.nit, sample areas (Table 1, Fig. 1). In 102 of the sample C.asp / V.pul, S.put / C.ede, S.put / C.asp, S.put / areas on Ruissalo, the most common species was V.pus, A.nit / V. c o s , A.nit / C.ede and A.nit / V.pus Nesovitrea hammonis, occurring in 75 sample ar- together were found in the sample areas. Memoranda Soc. Fauna Flora Fennica 86, 2010 • Table 1. Occurrence of the land snail species on the island of Ruissalo in relation to each other/occurrence correlation. The more common species (21) were examined. The species are arranged from the most common to the most rare. The numbers are percentages and the number of sample areas is in paren- theses (n = 102 sample areas). S Z.nit N.ham C.lub P.pyg E.ful C.bid D.rud N.pet V.pel V.sub V.pul C.ede C.asp F.fru V.cos V.pus C.lam E.str S.put A.nit T.his %(n) Z.nit 15 %(n) 40(6) 87(13) 73(11) 93(14) 33(5) 53(8) 33(5) 40(6) 40(6) 40(6) 07(1)27(4) 13(2) 0 13(2) 7(1) 47(7) 0 0 N.ham 75 8(6) 75(56) 56(42) 65(49) 61(46) 56(42) 61(46 60(45) 28(21) 11(8) 13(10) 29(16) 43(32) 8(6) 13(10) 19(14) 12(9) 9(7) 4(3) 15(11) C.lub 67 19(13)75(56) 64(43) 76(51) 63(42) 54(36) 63(42 55(37) 37(25) 22(15) 13(9) 29(16) 48(32) 12(8) 13(9) 15(10) 12(8) 15(10) 3(2) 16(11) P.pyg 52 21(11) 81(42) 83(43) 79(41) 67(35) 58(30) 62(32 52(27) 40(21) 23(12) 21(11) 25(13) 46(24) 12(6) 17(9) 19(10) 15(8) 17(9) 4(2) 17(9) E.ful 59 24(14)83(49) 86(51) 78(41) 78(41) 66(39) 54(32 51(30) 37(22) 22(13) 15(9) 29(17) 46(27) 12(7) 14(8) 17(10) 10(6) 17(10) 3(2) 17(10) C.bid 53 9(5) 87(46) 79(42) 66(35) 77(41) 57(30) 51(27 58(31) 40(21) 23(12) 17(9) 28(15) 57(30) 11(6) 17(9) 21(11) 17(9) 11(6) 4(2) 21(11) D.rud 47 15(7) 89(42) 76(36) 63(30) 83(39) 63(30) 62(29 51(24) 40(19) 15(7) 13(6) 30(14) 47(22) 13(6) 11(5) 19(9) 13(6) 15(7) 4(2) 9(4) N.pet 47 11(5) 99(46) 89(42) 68(32) 68(32) 57(27) 62(29) 49(23) 36(17) 11(5) 17(8) 23(11) 36(17) 6(3) 15(7) 23(11) 15(7) 6(3) 4(2) 15(7) Routio V.pel 53 11(6) 85(45) 70(37) 51(27) 57(30) 58(31) 45(24) 43(23 21(11) 9(5) 9(5) 21(11) 53(28) 9(4) 9(5) 13(7) 9(5) 15(8) 4(2) 13(7) V.sub 27 22(6) 78(21) 93(25) 78(21) 81(22) 78(21) 70(19) 63(17 41(11) 41(11) 26(7) 26(7) 55(15) 19(5) 7(2) 22(6) 19(5) 22(6) 7(2) 26(7) V.pul 15 40(6) 53(8) 100(15) 80(12) 87(13) 80(12) 47(7) 33(5) 33(5) 73(11) 20(3) 0 67(10) 27(4) 7(1) 13(2) 13(2) 33(5) 0 40(6) C.ede 12 0 83(8) 75(9) 92(11) 75(9) 75(9) 50(6) 67(8) 42(5) 58(7) 25(3) 33(4) 83(10) 12(1) 33(4) 42(5) 17(2) 0033(4) C.asp 19 2(1) 87(17) 84(16) 68(13) 89(17) 79(15) 74(14) 58(11 58(11) 37(7) 0 21(4) 58(11) 11(2) 21(4) 21(4) 11(2) 0 5(1) 11(2) F.fru 41 10(4) 78(32) 78(32) 58(24) 66(27) 73(30) 54(22) 41(17 68(28) 36(15) 24(10) 24(10) 29(11) 10(4) 17(7) 22(9) 12(5) 17(7) 2(1) 24(10) V.cos 8 25(2) 75(6) 100(8) 75(6) 88(7) 75(6) 74(6) 37(3) 50(4) 62(5) 50(4) 13(1) 25(2) 50(4) 25(2) 13(1) 25(2) 25(2) 0 25(2) V.pus 10 0 100(10) 90(9) 90(9) 80(8) 90(9) 50(5) 70(7) 50(5) 20(2) 10(1) 40(4) 40(4) 70(7) 20(2) 60(6) 30(3) 0020(2) C.lam 14 7(1) 100(14) 71(10) 71(10) 71(10) 78(11) 64(9) 78(11 50(7) 43(6) 14(2) 36(5) 29(4) 64(9) 7(1) 43(6) 21(3) 7(1) 7(1) 21(3) E.str 10 10(1) 100(10) 80(8) 80(8) 60(6) 90(9) 60(6) 70(7) 50(5) 60(6) 20(2) 30(3) 30(3) 50(5) 20(2) 30(3) 30(3) 10(1) 10(1) 40(4) S.put 13 54(7) 54(7) 77(10) 69(9) 77(10) 46(6) 54(7) 23(3) 61(8) 46(6) 38(5) 0054(7) 15(2) 0 8(1) 8(1) 0 31(4) A.nit 3 0 67(2) 100(3) 67(2) 67(2) 67(2) 67(2) 67(2) 67(2) 67(2) 00 33(1) 33(1) 0033(1) 33(1) 00 T.his 13 0 85(11) 85(11) 69(9) 77(10) 85(11) 38(5) 54(7) 54(7) 54(7) 46(6) 31(4) 23(3) 77(10) 15(2) 15(2) 23(3) 31(4) 31(4) 0 X = % 14,4 79,9 83,9 70,8 75,8 69,8 57,7 54,5 52,0 43,8 22,2 17,6 24,5 53,2 11,6 15,4 22,3 15,7 14,1 2,9 18,8 29 30 Routio • Memoranda Soc.