Table Of ContentLOCALDISTRIBUTION PATTERNS OFLAND SNAILS
IN RELATIONTO VEGETATION: IMPLICATIONS FORRESERVEDESIGN.
ROBERT TAYLOR ROBERTMESIBOV ANDIVOR GROWNS
J. ,
Taylor*RJ.,Mesibov,R.&Growns,1. 19940630: Localdistributionpatternsoflandsnails
in relation to vegetation: Implications for reserve design. Memoirs of the Queensland
Muscum36(\): 215-220. Brisbane. ISSN0079- 8835.
Distribution patterns of land snails amongst forest communities were studied in a 500ha
biockofStateforestinnorth-eastTasmania.Twelvespecieswerefound,fourofwhichwere
representedbyfewerthanfiveindividuals.Threeoftheeightcommonspecieswererandomly
distributed in relation to vegetation. Four others were most abundant in the wetter forest
communities,closetodrainagelinesoradjacentslopes.Theremainingcommonspecieswas
mostfrequently found in the driestcommunity. Retention ofstreamside reserves when the
area is logged would probably protect populations of all land snails. However, a more
comprehensivesystemofreservesincludingallmajorvegetationcommunitieswouldensure
protectionofpreferredhabitatforallspecies.^Molluscs,landsnails,distribution,regetasion
community, reservedesign,forestry.
RobertJ. Taylor, Forest Practices Unit, Forestry Commission, 30Patrick Street, Hobtirt,
Tasmania, Australia, 7(.KK>; Robert Mestbov, P. O. Box 700, Burrtte, Tasmania.Australia
7320; IvorGrowns, FisheriesResearch Institute, POBox 27. Cromdta, N.S.W., Australia
2230;30July1991
Because invertebrates, many undescribed, are STUDY AREA
sodiverse,aspecics-by-specicsapproach totheir
conservation is totally impractical. Conservation The study was undertaken on State Forest in
agencies in Australia art now mostly aiming to north-east Tasmania, in a SOOha block of
adopt a strategy of creating reserves to ensure sclerophyll forest to the north and south-west of
regional representation of vegetation com- Old Chum Dam (41°06,S, USTO'E). Altitude
munities. (Brown <fe Hickey, 1990; Common- varied from IO0-250mon an underlyinggeology
wealthofAustralia, 1992). Ithasbeenarguedthat of Ordovician granite, Average annual rainfall
ainvveergetteabtriaotne-bcaosnesdersvtraattieogny.wiIlnlvearltsoebcraatteer afso-r &wasBr9o7w8nmm(.19V9e3g)etwahtoiountiwlaissedstcuodvieedr-baybuDnudnacnacne
semblages are correlated wilh vegetation com- <Braun-BIanquet) floristic datato distinguish six
forestcommunities:
munities (Yen, 1987) However, distributions of
manyinvertebratesarenotinfluencedbychanges
in vegetation(Richardson, 1990) andspeciesap- (1)Blackwoodgullyforest
parentlyrestrictedtoonevegetationtypemaynot This forest was associated with gullies and
occur throughout it (Hill & Michaelis, 1988; ctrheeemk.liSnepsa,rsoeftcemnerfgoernmtisng(a30tmh+in) coofrrEiudcoarlyapltonugs
Cameron, 1992).
obliqua occurred over a dense secondary tree
Mesibov (1993) studied litter invertebrates in layer(20-30m)dominatedbyblaekwood[Acacia
north-western Tasmania in a 50 km2 with rain- melanoxylon). Dicksoniaantarctica, Oleariaar-
forest,weteucalyptforest/woodlandandtea-tree gophylla, Pomaderris apetala, Coprosma quad-
Leptospermum lanigerutn scrub. He concluded nfida and Bursaria spinosa formed a den*e
that most species ranged across all vegetation mediumtotallshrub-Jayer.Thegroundlayerwas
types. Distribution patterns of several inver- dominated by ferns,including Blechnumnudum,
tebrategroups across vegetationtypes at a much B. wansii&wd Polystichunxprolifeiurn. Low light
drier site in north-eastern Tasmania were here levels reaching the forest floor precluded
examined. Results for the land snails are development of herbaceous species but
presented. Snails were used as they were bryophytes werecommon.
taxonomically well known, easily identified,
numbers ofspecies and densities expected were (2)Eucalyptgully woodland
not excessive, and it was anticipated that they This was adjacent to creeks and gullies where
would be influenced by moisturegradients. microclimate was slighliy less humid and soil
.
216 MEMOIRSOFTHEQUEENSLAND MUSEUM
moisture highercompared with sites supporting very dense medium to tall shrub layer was
blackwood gully forest, The community com- dominated by M. squarrosa with L scoparium
prised woodlands, grading into forest, with £. and .4. vertkiUata also prominent. The ground
obliqua and occasional E. viminalis exceeding layer was often dense, being dominated by
30m. A medium to tall shrub layer and included sedges, fernsand graminoids.
eucalypts, P. apetala, Melaleuca squarrosa and
A. verticillata* Trunked ferns (Dieksonia, Todea (6)Heathydrysclerophyllforest
and Cyathea) were prominent The ground layer This community was widespread in the study
was very dense compared with blackwood gully area, occupying well-drained middle and upper
forest and was dominated by ferns with tall slopes subject to moderate drought stress. £.
graminoids prominent on poorly drained sites. amygdaltna was dominant with E. obliqua co-
Herbaceous species were sparse and bryophytes dominant or subdominant. The medium shrub
lesscommon than in blackwoodgully forest layer was very sparse and the low shrub/ground
layerwas moderately dense being dominated by
(3) Tall wetscterophyllforest bracken {P. esculentum) and L scoparium sug-
Thiscommunityoccurredonwelldrainedsoils gesting ahistory offrequent burning.
OH sourh-facing middle to lower slopes. The
upperstratumexceeded30mand wasdominated METHODS
by E. obliqua with E. viminalis a minor species.
The small tree and foil shrub layer was very All 116plots,eacha 10mdiametercircle,were
sparse. The medium shrub layer (I-5m) was located across the study area and stratified to
dense and mainly comprised P. apitata, sample the range of vegetation communities
Monatocaglauca.A. vertkiUata,Zteriaarbores- (blackwood gully forest, 14plots; eucalyptgully
censand Coprosmaquadrifida. A dense to very woodland,20: tail wetsclerophyllforest.7:damp
sclerophyll forest, 30; scrub woodland, 18; and
dense ground stratum, dominated by ferns (Cul* heathy dry sclerophyll forest, 27). Over27 days
ciia dubia and Pteridium esculeruum), was (IS May-23June 1989),snails weresearched(by
present in some areas. Graminoids. grasses and B.M.) 60minutesperplot. Areasexaminedwere
herbsweresporadic in occurrence \ shelteringsites:barkscrolls,basesofferns,
leaf liner including litter built up at the base Of
(4)Dampsclerophyllforest trees, loose bark, moss, rotting wood, bases of
This community w;is widespread, mainly oc- graminoids (e.g. Gahnia and Lomandra)* stones,
cupying slopes with south to cast aspects. Soils tree ferns and woody litter. For each plot, vari-
were well drainedand had moisture levelsinter- ables recorded were: slope, aspect, overstorey
mediatebetween wetanddrysclerophyll sites.E. age (mature or regrowth), plant species thatcon-
obliqua and/or E. amygdalina were dominant tributedsignificantlytocoverorprovided shelter
with £ viminalis .i tumor spe; ies The canopy for snails forboth the shrub layer (>lm) and the
wasdense between 20 and 30ro.The medium to ground layer (if ground cover was dense plant
tailshrublayerwas very sparse andmainly com- species contributing significantly to this cover
prisedA.termtnalisrA. vertkiUata, Olearialirara weregivenarating,of2.ratherthan I forjusttheir
and eucaJyptregeneration.Vegetation below lm presence), a shade rating on a 1-3 scale and the
was moderately dense with the relative abun- type of shelters searched. Snails of many of
dance of sclerophyllous shrubs (e.g. Pultenaea TasmaiuVs terrestrial species are small (< 3 or
juniperina. Lomatia tinctoria, Leptospermutn 4mm in shell width or height). Hence, some
scoparium) and bracken probably reflecting fire smaller snails would have been missed on some
history. Graminoids, herbs and grasses were plots. However,searcheffortwasconsistentover
sparse but more prominent than in the wetter the plots. Hence, results from different plots
forestcommunities. .should becomparable.
(5)Scrubwoodland NUMERICALANALYSIS
This community wits strongly associated with
basins and soakages with impeded drainage. £. Ordination of snail data was carried out using
obliqua and/or E. amy$dalina were dominant. semi-strong hybrid multidimensional scaling
Treeswere sparser, lower in heightand poorer in (SSH) in the PATN software package (Belbin,
formthanthose in sumwndingforest. Adenseto 1988) The Bray-Curtiscoefficient was used asa
LANDSNA1L5 AND RESERVEDESIGN 217
measure ofdissimilarity between samples after and unlikely W have been missed. All four
standardisingdatabysubtract!ngminimumabun- Thryasona diemenensis were found on one plot
dance of a taxon and dividing by its range lo at the head oi a gully in blackwood gully fores*
reducetheweightingofabundanttaxa.Thenum- Miselaoma parvissima and Paralaonta
berofdimensionsrequiredfortheordinationwas caputspinulae were found in heathy dry
assessedby examiningstress levelsasa function sclerophyll forestandoneindividualofRoblinel-
of the number of dimensions from 10 random ia gadensis was found in each of eucalyptgully
starts. The chosen number of dimensions was woodland and tall wel sclerophyll forest. These
then used in 100 random starts and the one with fourspeciesarenotconsideredfurtherduetotheir
the lowest stress used.The relationshipbetween low frequencies ofoccurrence,
(he ordination spaceand the abundances of sn.nl Two plots yielded no snails and were not in-
species and the environmental variables were cluded in the ordination. Four dimensions were
examined using the Principal Axis Correlation required todescribe lheordination ofthe plotson
(PCC)procedureinthePATNprogram. ThePCC the basis of the abundance of snail species.
procedure determines the best linear fit between Caryodes dt<Jresnii> IteUrorion cuvten and Tas-
ordination vectors and the variable under con- mudelos nelsonensis appeared to be randomly
sideration(Be(bm, 1988).Theoverallcorrelation distributed amongst vegetation communities
cstoaetfifsitciciaelntssigdneitfeircamnicneedbybuysiPnCgC10w0erMeon&tteseteCdarfloor a("btuanbdlean1tanindsFcigr.ub1)w.»Cny>sdtlcapnedhabputetotcecrudrirewdasacmroossts
randomisations of the data set (Faith Norris,
thefull rangeofvegetation types being lowest in
1989).
abundance in blackwood gully forest. Den-
The distribution ofsnails in relation to vegeta-
therona subrugosa was most abundant in black-
tion communities was examined to see whether
wood gully forest and occurred in low numbers
theobserved patterns could be explained by ran-
dom processes atone, The Group Definitions in other wettercommunities. Ehothera ricei oc-
module in PATN was used for thisanalysis The curredacrossall vegetationcommunitiesbut was
data foreach species were randomised most abundant in the gully types. Tasmaphena
100 times (Motae Carlo randomisa- —
tions) and Cramer values calculated. Species Total CramerValue Vectorcoefficient
These values are the between-group No. (Significance) r{Significance)
variance divided by the total variance CARYODfDAE
andran^e from0> where nodiscrimina- Canodesdufresnii 50 0.21 (n.s.) 0.36(n.s.)
tion between groups exist, to 1, where CHAROPIDAB
perfect inter-group discrimination oc-
Deutheroriasubnifiosa 3: 0.66K0.05) 0.58(<0.05)
curs. If the Cramer value for lhe actual
duta was greater than 95 ofthe Cramer Elsotheraricei 240 0.43K0.05) 0.62K0.05)
values from the randomised data sets Pernagentofftcen 118 0.36K—0.05) 0.78(—<0.05»
lhe observed patterns were considered Thryasonadiemensix 4 — —
to represent a non-random distribution Hnbhnelkigadensis 7
amongst vegetation communities. The CYSTOPELTIDAE
significanceofdifferencesbetween fre- Cyxiopehapetterdi 290 0.42(<0.05i O.55«0.05)
quencies of occurrence in different HKUCARIONIDAE
categories was determined using Chi-
Helicanoncuvieri 406 0.25(n.s.| 0.82<<a05>
squarc tests.
KHY1IDIDAE
RESULTS Tastnadelosnehonenns 34 0.25(n.s.) 0,78(<tU)5>
TasmaphenasineU:\ri rs 0.32<<0.05) 032<jvb.i
Twelve species of land snail were PUNCITDAE
foundonthestudyarea(Table I).Ofthe Paralanmacaputsprnuttw 2 —
four species (or which fewer than five — —
individuals were located, threeare very Miselaotnoparvissima 1
small (less than 3mm) and this may
partlyexplainwhyfewindividualswere TABLE 1.Totalnumbertit eachspeciesofsnail foundinlhestudy
areaalong with an index oftheirdiscrimination between vegcta-
taken. The fourth species, TUrwsona iion types(Cramer value) ondthe correlation coefficient offljrir
diemenensis, however, is conspicuous vectorofmaximumcorrelation wilhin theordination space.
218 MEMOIRSOFTHEQUEENSLANDMUSEUM
Snails
C.petterdi
H.curx'ieri
5 o-
T,sim-fian
P.afficeri
KGW TWSF HDSF D sitbruROM E.ricei
Vegetation Community
Vector 2
C.petterdt
E,ricei
H.cuvicri B Environmental variables
L,stoparium
^P.apetala
EGW TWSF DaSF ScW HDSF
Vegetation Community C,quaJr
\.mclanoxylon
Shade
P.proliferiim
KM!
C
dufresnii
T.nelsonensis Vector 2
B
T.sinclairi
FIG. 2. Directionsofvectorsofmaximumcorrelation
a ft' with the ordination space for snail plots for each
species (excluding 4 rare species) and for environ-
mentalvariablesshowingsimilardirectionstothatof
the snails. Vectors of similar length and direction
indicate co-occurrence of snail species and/or en-
vironmental variablein theordinationspace.
sothera ricei and Tasmaphena sinclairi had
BGF EGW TWSF DaSF ScW similar vectors of maximum correlation within
Vegetation Community the ordination space. However, the vector for
Tasmaphenasinclairiwasnotsignificant,possib-
FIvGe.get1a.tDieonnsictoymmoufnisntayi,l sBpeGcFies=(Nbol.a/ckhaw.o)odingeualclhy ly due tothe low abundance ofthis species. The
forest,EGW=eucalyptgullywoodland,TWSF=tall vectors for environmental variables associated
wet sclerophyll forest, DaSF = damp sclerophyll with the wetter vegetation communities (D. an-
forest, ScW = scrub woodland and HDSF= heathy tartica, r=0.49; P. apetala* r=0.35; A.
drysclerophyllforest. melanoxylon, r=0.51; C. quadrifida^ r=0.40; P.
proiiferum, r=0.44; and shade, r=0.42) had a
sinclairi was also most abundant in the gully similar direction to that of Dentherona sub-
communities. Incontrast,Pernageraofficer!was rugosa, Elsothera ricei and Tasmaphena
most abundant in the driest community, heathy sinclairi. For Dentherona subrugosa and El-
dry sclerophyll forest. sothera ricei the proportion of plots containing
These patterns are confirmed by theordination these snails variables was significantly greater
(Table 1, Fig 2). Dentherona subrugosa, El- (Chi-squared tests) where the above mentioned
LANDSNAILS AND RESERVEDESIGN 219
plants were present (or where shading was wood gully forest, is puzzlingtas it is very com-
greater) than for those plots were they were ab- mon in north-east Tasmania in a wide varietyof
sent (or where shading was low). This was also wet habitats and even some dry areas (K- Bon-
the case for Tasmaphenasinclaiributsometimes ham, pers. comm.).
not significantly so, probably due to fewer Results here are similar to those of Mesibov
specimens.ThevectorforPernageraofficeriwas (1993) on litterinvertebrates in north-west Tas-
L
similar to that for tincioria (r=0.49) and to a mania in that mostspeciesrangedacrossmostof
lesser extent L scoparium (r=0.44) (Fig. 2). vegetation types. Both studies also found a
Neitherplant species occurred in the gully com- minorityofspecies wererestrictedtooneorvery-
munities but ranged across other vegetation few of the range of vegetation types examined.
types. L. scoparium was the main low shrub Mesibov's (1993) study also found distinct dif-
species in the driest community, heathy dry ferencesin densities ofsome species in different
sclcrophyll forest. The proportion of plots con- vegetation types, as i>ui study did.
taining Pernagera officeri was significantly Because many invertebrates have restricted
greaterwhereL tmctoriaandL scoparium were distributions, any generalised reserve system for
present than for these plots where these plants invertebrate* would need to include reservation
were absent. Caryodes dafresnii was randomly ol habitat al a localised level to supplement a
distributedintheordinationspaceandin relation regional vegetation based reserve system. Sam-
to vegetation communities. Cystopelta petterdi plingofvegetationtypesand/orlandformsshould
andHelicorioncuvierihadvectors in theordina- be undertaken comprehensively in such a
tionspacethatweredissimilartoallotherspecies localised reserve system a* well as at a broader
and to each other (Fig. 2) and these species' regional scale. Our study area occurs in State
vectorsdidnotclosely relatetoany vectorsot the Forest. Until recently, the only systematic reser-
environmental variables. Helicorion cuvieri had vations at a local level m Stale Forests were
the strongest vector ofmaximum correlation in slreamsidc reserves, designed to protect water
theordinationspace. However, itspatternofdis- quality. These reserves extend from 20 to 40m
tributionappearednottorelatetovegetation This either side of streams depending on stream and
was also the case for Tasmadehs nelsonensis protectall streams with a catcJimertt greater than
which hadthe next strongest vector. 50ha(Forestry Commission. 1993). These reser-
An examination ofoccurrence ofsnail species ves are thus biased towards wetter communities
in different types of shelters (= microhabitat ingulliesand areasofimpededdrainage. Stream-
usage)reinforcedthepatternindicatedbyvegeta- side reserves in the present study ;»»eu would
For example, Dentherona subrugosa was probably protect populations of most species.
restricted to the wetter gullies and was sig- since most are widespread and/or have wetter
nificantlyassociatedwith tree fern (/>. antartica) forest types as their favoured habitats. However,
heads as a shelter site. Tree ferns in turn were Pernageraofficeri,whichreachesitshighestden-
restricted to wettergullies sitiesinthedriest vegetationtype,wouldbepoor-
ly represented in such reserves. The preferred
DISCUSSION habitatsforallspeciesshould beincluded within
reserves. Retentionof lOOm-widestrips(referred
to as wildlife habitat strips), which also include
Vegetationpatternsinthestudyareaarestrong- areas of slope and ridge and hence more com-
ly related to topography via its influence on prehensively sample vegetation types at a local
pdrroatiencatgieo(nafndrotmhusfisroeil(mDouinsctaurne)&,sBoirlofwenrt,ili1t9y9A3n)d. level,hasthereforebeenintroducedmTasmanian
Stale Forests (Taylor, 1991). Such measures
Beltersoils with ahigh organiccontentoccuron
should better provide for the conservationof in-
thelowerslopesandingullies,andtheshallower.
vertebrau
more sandy soils occuron theridges and steeper
slopes. The distributions of three snails ACKNOWLEDGEMENTS
(Caryodesdufresnii, H. cuvieri and Tasmadehs
fu-lsonensis) wcie not relatedto these vegetation
patternsandall threewerewidespreadacrossthe Staff from the Fingal district of the Forestry
study area. Distributions of other species were Commission,particularlyMickMillerandLaurie
related to vegetation patterns but none were Gregson, provided logistical support. Ron Kci-
restricted to otic vegetation type. The single site shawassisted with snail identifications. Accom-
occurrence ofThryasonadiemenensis, in black- modationinthefieldwasprovidedbyMrandMrs
220 MEMOIRSOFTHEQUEENSLANDMUSEUM
D. Jennings ofTelita. The study was funded by HILL.L.&MICHAELIS,F.B. 1988. 'Conservationof
the Forestry Commission of Tasmania and the insectsandrelatedwildlife*.OccasionalPaperNo.
Tasmanian ForestEcology Research Fund. 13 (Australian National Parks and Wildlife Ser-
vice: Canberra).
LITERATURECITED HILL, M.O. 1979. Twinspan: A FORTRAN program
forarrangingmultivariatedatainanorderedtwo-
way table by classificationofthe individuals and
BELBIN, L. 1988. 'PATN reference manual* (CSIRO attributes'(CornellUniversity:IthacaNewYork).
DivisionofWildlife and Ecology: Canberra).
BROWN, M. & HICKEY,J.1990. Tasmanian forest, MESIBOV,R. 1993.'Species-levelcomparisonoflitter
CAMEgRenOeNs,orRw.iAl.dDer.ne1s9s9?2.SeLaarcnhd2s1n:ai8l6-f8a7u.nas of the nionvretrhtweebsrtaTteassmafnrioam*.tThraesemavneigaentaNtiRoCnPtTyepcehsnii-n
Napier and Oscar Ranges, Western Australia; cal ReportNo. 13. Forestry Commission, Hobart
and Department ofEnvironment, Sport and Ter-
diversity, distribution and spcciation. Biological
JournaloftheLinneanSociety45: 271-286. ritories,Canberra.
COMMONWEALTH OF AUSTRALIA 1992. 'Na- RICHARDSON, A. 1990. The implicationsofvegeta-
tional forest policy statement: A new focus for tion change for animals and their habitats. Tas-
Australia'sforests* (CommonwealthofAustralia: forests2: 173-178.
Canberra). TAYLOR, R. J. 1991. The role of retained strips for
DUNCAN, F.& BROWN,M. 1993. VegetationatOld fauna conservation in production forests in Tas-
ChumDamin north-eastTasmania. Unpublished mania. Pp265-270, In Lunney, D. (ed.), 'Conser-
Report(Forestry Commission, Hobart). vation of Australia's Forest Fauna' (Royal
FAITH, D.P. & NORRIS, R.H.1989. Correlation of Zoological SocietyofN.S.W.: Mossman).
environmentalvariableswithpatternsofdistribu- YEN, A.L. 1987. A preliminary assessmentofthe cor-
tion and abundance ofcommon and rare fresh- relation betweenplant, vertebrate andColeoptera
water macroinvertebrates. Biological communities in the Victorian mallee. Pp. 73-82,
Conservation50: 77-98. In Majer, J.D.(ed.) 'The Role ofInvertebrates in
FORESTRY COMMISSION 1993. 'Forest practices Conservation and Biological Survey'. (W.A.
code*. (Forestry Commission of Tasmania: Dept. of Conservation and Land Management:
Hobart). Perth).
