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O Hungarian Natural History Museum and Hungarian Academy of Sciences
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AN INTERNATIONAL JOURNAL OFANIMAL TAXONOMY AND ECOLOGY
Acta Mologica Academiae Scientiarum Hungaricae is published quarterly stombebruary l 994 sother issues in May. August and November) by the Hungarian Natural History Museum and the Biological Section of the Hungarian Academyos Sciences with the financiat support of the Hungari an Academy of Sciences.
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Acta Mologica Academiae Scientiarum Hungiariciae 46 4); py. 26 274. 2000
THE RELATIVE IMPORTANCE OF EDAPHIC FACTORS ONTHE DISTRIBUTION OF SOME TERRESTRIAL GA STROPOD SPECIES: AUTECOLOGICA L AND SYNECOLOGICALAPPROACHES
An autecological method secological profites analysis) and a synecological method scanonicalcorrespondence analysis) were used to investigate relationships belween edaphic factors and the distribution os terrestriat gastropolis in northwest Spatia. Gastropods were sampled Domi PT sites in this region. In generat, the two methods of analysis yielded similar resulis. The resulis stlow the importance of the influence of soli texture clay, coarse sand and gravet Content), pH, Calcium, magne Sitim. moi Sture, porosi ty, nitrogen and carbon on the distribution os terrestriat gastropod species in the stud ted area. Key woriis: land snails, edaphic factors, auteCOlOgy, Synecology
BRUIIINS etal. l 959) stated that, apari frona climate, the most important fac tors governing the distribution os terrestriat gastropods are edaphic factors. The influence of edaphic factors on the distribution os terrestriat gastropods is weli documented. Severat authors discus sed the relationship between en Viron mental charac teristi cs - edaphic factors pH. Soli moisture, calcium, SOil texture, etc.) and
Sium and principally, calcium storage compariments in s lugs and snails include the sheli. the calcium celis in the digestive gland s. the integument and the connective tis sue: so these elements are very important for the growth of the sheli an dother physiological processes SOUTH l 992). The soli texture gravet, poros ity, clay, Sand, Sili, etc.) i S also important in determining the distribution os gastropodsdistribution because gastropods have limited capacity for burrowing into the sollwhere it lays iis eggs or feeks refuge BOYCOTT l 934). With respect to the humid-ity snails and principalty slugs are restricted in their habitats by the need to avoid
desiccation: consecuently they are more active at night or in wet weather. On theother hand the association of snail-faunas, characteri sed by high abundance and
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Various statisticat methods are avat labie for investigat ing relationships be- tween edaphic factors and species distributions with in a gi ven area. Some of tho se methods are based on an autecological approach i. e. , independent analysis of the distribution of each species), and others on a Synecological Appi ORCh i. e. , analy Si Sof the effecis of each factor on the distribution of the species set). In the work reported here we investigated the influence of edaphic factors onthe distribution os terrestriat gastropolis in notiti est Spatia, and compared the resulis obtained using an autecological approach secological profites analysis) described by DAGET and GODRON sl 982), and a synecological approach canonical Corresponde iace analysis). The de vel opinent of synecological mei hods is linked tomulti variate statistical analysis. These analyses have been greatly improved in recent years, with the introduction os techni ques specifical ly designe d for ecology one of whicli is canonical corresponde iace analysis TER BRA AK l 986).
Terrestriat gastropods were sampled at lJJ sites in the Provinces os Asturias; Leon. Zamora and Salamanca in northwest Spatia. Terrestriat gastropods were sampled in βψ areas of this region hywet si eving WlLLIAM SON l 959) of the top 5 cm os litter and soli frona an area os O. my. At cach si te soli samples were also collected. sor subsequent determination Os 20 physical and chemicat properties fas described by GUlTIAN & CARBALLAS l9J6) soli moisture, poros ity, Acration, graVel, COII SCsanit, fine sanit, coarse fili, sine Sili, clay, carbon, nitrogen, carboninit rogen rntio, SOdium, potasSi Urn, Culcium, magnesium, aluminium. pH os soli in water. pH of soli in KCl and pH os littor in water. Speciosis ite data were analysed by canonical corresponde iace analysis CCA) and ecologicalprosiles analysis. A synecological stud y allowed tis to investigate the relations hips he tween en viro n-mental factors and the distribution os species grotips, and converse ly aid identification Os species groups with similar distributions in en viro iamentat hypei space TER BRA AK l 986). The data were analyscd by CCA in CANOCO version 3.l: TER BRA AK l 988). with Monte Cario testing to evaluatethe statistical signi sic ance of the Ouico me. An autoccological study allows his to analyZe each species individual response in Order to deieci their preseruncos sor specific interva is of the factors mea sui ed. The most appropriate technique for this is ccological prositos analysis. Ecological prosiles have greater po wer os discrimination whicli makes it possibi e to seu the species profercnces sor cither low. average or high values of a sactor, as weli us indisseretice to a particular factor. Class intervals were determined in ternas of in sicc-tion potnis on the curve os accumulaled frequenci cs DAGET & GODRON l 982): thorcsore we haveol,lained a similar number os samples in cach class. Corrected freque iacies C K)) were calculated sorthe disserent sta ait species as sol lows
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where V K) occurrences os species E in sactor class K. U E)α total number os occurrences os species E. R K)α number of samplus sor sactor class K and NR total numberos samples. Chi/-tests were carried out to determine whether the observed prosile distributions in relation to factors deviatod signi sicantly si ona uniformity.
A total of J3 species were identis ted in otir samples. The morphology of thesheli and genital system were the characters used for the diagno sis of the gastropolis. For determining specimens ait ille avat labie literature has been re vie wed and considere d. In what illo S, we consider only tho se species present in at least l0Rof samples, nam ely Arion intermedius NORMAND l852, Acanthinula iaculeata
The fit st two axes explatia 59 βδ of totai variance in the data. Monte Cario permutation testing as per HOPE l 968. in TER BRA AK l 988) of the outcome of CCA indicate that axis I is significant at the 99 δ levet F ratiora l3. 03: pQ0. 0 l) and axis two at the 9 β in levet F ratio: 6.l 9: pQ 0. Ob): axis III was not significant. Interset correlation coefficients are listed in Table to the factors that are most closely correlated with axis I are M g, Ca pH, C, N, gravel and clay content, moi Sture and porosity the factors that are most closely correlated with axis II are gravel and coarse sanit
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I. HERMIDA. M. P. ONDINA & T. RODRIGUEZI ahle 1. Interset coefficients of correlation belween edaphic factor values anil sample scores on thesirst two axes extracted by canonical correspondeiace analysis of the ten species data set. HUM soll
coni se sand content, and Arion intermedit S and Uitrea contracta, located close tothe origi n. not show clear prefere iaces for any factor.
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Ecological profites is an auloecological method. which allow us to determine whicli edaphic factors are probab ly more imponant for each species: also it is possibi e to determine the species' preferen ce for mean values of the factor and indicates the intervals of the factor values in which the species is present Fig. 2). The